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Status of the
Slender Mouse-ear-cress
( Halimolobos virgata or
Transberingia bursifolia subsp. virgata)
in Alberta:

SPECIES AT RiSK

Update 2009

Government
of Alberta ■

Alberta Conservation
Association

Digitized by the Internet Archive
in 2016

https://archive.org/details/statusofslenderm00brad_0

Status of the Slender Mouse-ear-cress
{Halimolobos virgata or
Transberingia bursifolia subsp. virgata )

in Alberta:

Update 2009

Prepared for:

Alberta Sustainable Resource Development (ASRD)
Alberta Conservation Association (AC A)

Update prepared by:

Cheryl Bradley

Much of the original work contained in the report was prepared by Ian Macdonald in 2005.

This report has been reviewed, revised, and edited prior to publication.

It is an ASRD/ AC A working document that will be revised and updated periodically.

Alberta Wildlife Status Report No. 55 (Update 2009)
August 2009

Published By:

Government
of Alberta ■

Alberta Conservation
Association

Publication No. T/218
ISBN: 978-0-7785-8715-6 (Printed Edition)
ISBN: 978-0-7785-8716-3 (On-line Edition)
ISSN: 1206-4912 (Printed Edition)
ISSN: 1499-4682 (On-line Edition)

Series Editors: Sue Peters, Robin Gutsell and Gavin Berg
Illustrations: Brian Huffman
Maps: Velma Hudson

For copies of this report, visit our web site at:
http ://srd. alberta, ca/fishwildlife/ speciesatrisk/
and click on “Detailed Status”

Contact:

Information Centre - Publications
Alberta Sustainable Resource Development
Main Floor, Great West Life Building
9920 - 108 Street

Edmonton, Alberta, Canada T5K 2M4
Telephone: (780) 944-0313 or 1-877-944-0313

This publication may be cited as:

Alberta Sustainable Resource Development and Alberta Conservation Association. 2009. Status
of the Slender Mouse-ear-cress ( Halimolobos virgata or Transberingia bursifolia subsp. virgata)
in Alberta: Update 2009. Alberta Sustainable Resource Development. Wildlife Status Report
No. 55 (Update 2009). Edmonton, AB. 28 pp.

PREFACE

Every five years, the Fish and Wildlife Division of Alberta Sustainable Resource Development
reviews the general status of wildlife species in Alberta. These overviews, which have been
conducted in 1991 ( The Status of Alberta Wildlife ), 1996 ( The Status of Alberta Wildlife ), 2000
(The General Status of Alberta Wild Species 2000), and 2005 (The General Status of Alberta Wild
Species 2005 ) assign individual species “ranks” that reflect the perceived level of risk to populations
that occur in the province. Such designations are determined from extensive consultations with
professional and amateur biologists, and from a variety of readily available sources of population
data. A key objective of these reviews is to identify species that may be considered for more
detailed status determinations.

The Alberta Wildlife Status Report Series is an extension of the general status exercise, and
provides comprehensive current summaries of the biological status of selected wildlife species
in Alberta. Priority is given to species that are At Risk or May Be At Risk in the province, that are
of uncertain status (Undetermined), or that are considered to be at risk at a national level by the
Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

Reports in this series are published and distributed by the Alberta Conservation Association and
the Fish and Wildlife Division of Alberta Sustainable Resource Development. They are intended
to provide detailed and up-to-date information that will be useful to resource professionals for
managing populations of species and their habitats in the province. The reports are also designed to
provide current information that will assist Alberta’s Endangered Species Conservation Committee
in identifying species that may be formally designated as Endangered or Threatened under Alberta’s
Wildlife Act. To achieve these goals, the reports have been authored and/or reviewed by individuals
with unique local expertise in the biology and management of each species.

iii

EXECUTIVE SUMMARY

Slender mouse-ear-cress ( Halimolobos virgata or Transberingia bursifolia subsp. virgata) is an
herbaceous plant distributed in the mixedgrass prairie on the plains of southeast Alberta and
southwest Saskatchewan, and across semi-arid mountain ranges and intervening basins and
plateaux of seven western states. It is listed as Threatened federally and also provincially by
the Saskatchewan government. In Alberta, evaluation of a 2005 provincial status report resulted
in a recommended status of Data Deficient by the Alberta Endangered Species Conservation
Committee and its Scientific Subcommittee. Results of additional surveys in known and potential
habitat for slender mouse-ear-cress are incorporated into this updated status report to assist in the
evaluation of its provincial status.

Suitable habitat for slender mouse-ear-cress in Alberta is characterized as undulating to rolling
native grassland on silty to sandy deposits of fluvial or eolian origin. It may be associated with
ephemerally wet depressions and drainages. Fourteen subpopulations are recognized in Alberta:
one is ranked as extirpated, one as historical, three as failed-to-find during subsequent surveys and
nine as extant. Substantial rare plant search effort over the last few decades, and particularly within
the last few years, in apparently suitable habitat has resulted in reports of only a few additional
subpopulations of slender mouse-ear-cress. The extent of occurrence of all subpopulations in
Alberta is about 9998 km2; that of only extant ones is about 530 km2. Considering only extant
subpopulations, the area occupied by slender mouse-ear-cress is estimated to be 18 km2 (the
sum of occupied 1-km x 1-km squares). This number could be less than 0.05 km2, based on
the number and maximum size of unique locations in the Alberta Natural Heritage Information
Centre database.

The provincial population of slender mouse-ear-cress is estimated to be in the order of several
thousand (3000-7000) reproducing individuals in years when conditions are suitable for
germination and growth. Data over multiple years at some sites indicate large fluctuations in
number of reproducing individuals, depending on environmental conditions such as timing
and amount of rainfall in spring. Alberta’s extant population of slender mouse-ear-cress is
approximately 45 km from the closest known subpopulation in Saskatchewan and 200 km
from the nearest subpopulation in the Sweetgrass Hills of Montana. The next nearest known
populations are about 450 km south in the Tendoy Mountains of southwest Montana and in the
Absaroka Range of northwest Wyoming.

Loss of native grasslands within the range of slender mouse-ear-cress is affecting habitat quality
and availability. Native prairie decline is caused primarily by agriculture expansion, urban
development, oil and gas development and the construction of transportation and utility corridors,
as well as the spread of invasive non-native species in fragmented landscapes. Since 1970, bare
ground resulting from agriculture (cultivation) and industrial development has increased 40%
and linear disturbance has increased 93% in a regional study area that encompasses all of the
range of extant slender mouse-ear-cress subpopulations. The trend in loss of native grasslands
is expected to continue. Other potential limiting factors for slender mouse-ear-cress are climate
change and altered fire and grazing regimes beyond the range of natural variation.

A draft recovery strategy for slender mouse-ear-cress in Canada has recently been developed by
Environment Canada.

ACKNOWLEDGEMENTS

For the original 2005 report prepared by Ian Macdonald:

Bonnie M. Smith (University of Calgary) for her generosity in sharing her experience with the
species in Alberta, without which this report would not be possible; Candace Elchuk (Canadian
Wildlife Service [CWS]) for sharing information on her relocations in the province from 2004,
and for her fresh insight into the habitats of the species; Susan Peters (Alberta Conservation
Association [AC A]) for her encouragement in the field survey and research phases of this project
and her excellent, thorough and insightful review of this report; Andy Didiuk (CWS) and Robin
Gutsell (Alberta Sustainable Resource Development [ASRD]) for their support of the 2002 and
2003 field survey and research phases of this report; Nyree Sharp (AC A) for her review of the final
stages of this report; Ksenija Vujnovic (Alberta Natural Heritage Information Centre [ANHIC])
for providing information on the known sites in Alberta; John Rintoul (ANHIC) for information on
the reported Rosedale and Cypress Hills sites and conservation issues in Alberta; Sheila Lamont
(Saskatchewan Conservation Data Centre [SCDC]), Jeff Keith (SCDC) and Ann Gerry (SCDC)
for information on the recent efforts to locate the species in Saskatchewan and clarification of
the Cypress Hills sites; Mike Shchepanek (The Canadian Museum of Nature) for locating H .J.
Scoggan’s original data file record of M.E. Moodie’s 1914 collection from the Rosedale location,
and to Dr. Marcia Waterway (McGill University), Dr. Paul M. Catling (Agriculture and Agri-
food Canada) and Christine Niezgoda (Vascular Plant Herbarium, Field Museum, Chicago, IL)
for their searches for the actual Rosedale specimen; Bonnie Heidel (Wyoming Natural Diversity
Data Center) for sharing her information on the species’ habitats and distribution in Wyoming and
Montana, and for providing the invaluable correspondence with Walter Fertig (Grand Staircase-
Escalante National Monument) on his knowledge of the locations and habitats for the species
in Wyoming and Montana; Dr. C.C. Chinnappa (University of Calgary) for allowing access to
the herbarium collections; Bob Hale (Duchess Community Pasture Association) and Fred Wittig
(Landowner, Burstall, SK) for providing grazing management information on the locations under
their management in Alberta; Jane Lancaster (Kestrel Consulting) for sharing her information on
the species in Alberta; Garry C. Trottier (CWS) for updated information on the species’ location
in Canadian Forces Base Suffield National Wildlife Area; Dr. Geoffrey L. Holroyd (CWS) for
information on remaining native prairie in western Canada; and Hugh D.J. McLean (Agriculture
and Agri-Food Canada) for information on prairie climate and drought conditions.

Preparation of this report was funded by the Alberta Conservation Association and the Fish and
Wildlife Division of Alberta Sustainable Resource Development.

For the 2009 update prepared by Cheryl Bradley:

The assistance and contributions of several people in the preparation of this report is gratefully
acknowledged. Lome Fitch assisted with field work in 2008. Todd Kemper (Alberta Natural
Heritage Information Centre) provided data on occurrences of slender mouse-ear-cress in Alberta
and worked to jointly resolve issues about the definition of subpopulations. Gavin Berg (Alberta
Sustainable Resource Development, ASRD) assisted in acquiring background information. Ian
Macdonald (botanical consultant) provided background information on the 2005 status report
that he wrote and reviewed collections of slender mouse-ear-cress in the University of Calgary
herbarium. Bonnie Smith (botanical consultant) provided information on previous field work and
collections. Ihsan Al-Shehbaz (Missouri Botanical Garden) provided label information for an

historical collection near Rosedale and insights into revisions to the taxonomy of slender mouse-ear-
cress. Darcy Henderson and Candace Neufeld (Canadian Wildlife Service, CWS) shared information
on occurrences of slender mouse-ear-cress in Saskatchewan, key field identification characters and
appropriate survey techniques. Bonnie Heidel (Wyoming Natural Diversity Database), Peter Lesica
(University of Montana) and Scott Mincemoyer (Montana Natural Heritage Program) helped with
obtaining information on occurrences in Montana. Information on recent rare plant search effort in
potential habitat for slender mouse-ear-cress was shared by fellow botanists Dana Bush (Bush Ecology),
Jane Lancaster (Kestrel Research), Clare and Kathy Tannas (Rangeland Consultants), and Cliff Wallis
(Cottonwood Consultants), as well as by Albert Lees (Jacques Whitford Axys Ltd.). Velma Hudson
(Alberta Conservation Association, ACA) helped with production of maps. This report benefited from
reviews by Bonnie Smith, Dana Bush, Sue Peters (ACA), Gavin Berg and Robin Gutsell (ASRD).

Preparation of this report was funded by the Alberta Conservation Association and the Fish and
Wildlife Division of Alberta Sustainable Resource Development.

TABLE OF CONTENTS

PREFACE iii

EXECUTIVE SUMMARY iv

ACKNOWLEDGEMENTS v

INTRODUCTION 1

SPECIES TAXONOMY 1

HABITAT 2

1. Habitat Attributes 2

2. Habitat Trends 3

CONSERVATION BIOLOGY 5

DISTRIBUTION 6

1. Alberta 6

2. Other Areas 12

POPULATION SIZE AND TRENDS 12

1. Alberta 12

2. Other Areas 15

LIMITING FACTORS 16

1 . Loss and Degradation of Habitat 16

2. Anthropogenic Climate Change 16

3. Altered Fire Regime 17

4. Altered Grazing Regime 17

STATUS DESIGNATIONS 18

1. Alberta 18

2. Other Areas 18

RECENT MANAGEMENT IN ALBERTA 18

vii

TABLE OF CONTENTS continued:

SYNTHESIS 19

LITERATURE CITED 21

Appendix 1 Definitions of status ranks and legal designations 27

LIST OF FIGURES

Figure 1 Occurrence record locations for slender mouse-ear-cress in Alberta 7

Figure 2 Distribution of slender mouse-ear-cress in North America 13

LIST OF TABLES

Table 1 Summary of data on number of plants for occurrences/subpopulations of slender
mouse-ear-cress in Alberta 8

viii

INTRODUCTION

Slender mouse-ear-cress (. Halimolobos virgata
[Nutt.] O.E. Schulz; recently changed to
Transberingia bursifolia subsp. virgata ) is
an annual, biennial or short-lived perennial
herbaceous plant found in mixedgrass prairie
on the plains of southwest Saskatchewan and
southeast Alberta, and in the Sweetgrass Hills
of northern Montana. It is also distributed
across the semi-arid mountain ranges and
intervening basins and plateaux of seven
western states, from eastern California and
central Colorado north to southwest Montana
and northwest Wyoming. The other subspecies
of Transberingia bursifolia in Canada occurs
north of the Arctic Circle. Despite extensive
survey effort in Alberta, the known population
of slender mouse-ear-cress is estimated to
be in the order of several thousand (3000-
7000) reproducing individuals in years when
conditions are favourable. Loss of native
grasslands within the range of slender mouse-
ear-cress is reducing habitat quality and
availability.

Slender mouse-ear-cress is considered May
Be At Risk * according to the 2005 general
status review (Alberta Sustainable Resource
Development [ASRD] 2007). Evaluation of
the 2005 slender mouse-ear-cress status report
(ASRD 2005) resulted in a recommendation of
Data Deficient in 2005 (Alberta Endangered
Species Conservation Committee Scientific
Subcommittee 2005). In Saskatchewan, slender
mouse-ear-cress is listed as Threatened under
that province’s Wildlife Act (Government of
Saskatchewan 2008). Based on an assessment
by the Committee on the Status of Endangered
Wildlife in Canada (COSEWIC) in 2000,
slender mouse-ear-cress is listed as Threatened
in Canada, and is on Schedule 1 of the
federal Species at Risk Act (COSEWIC 2000,
Government of Canada 2008).

* See Appendix 1 for definitions of selected status
designations.

The purpose of this report is to summarize
current and historical data on slender mouse-
ear-cress in Alberta, in order to re-assess the
status of this species and develop conservation
strategies.

SPECIES TAXONOMY

Slender mouse-ear-cress from the western
United States and Canada was originally named
Sisymbrium virgatum Nutt ex Torrey & A. Gray
in 1838. In 1924, it was re-named Halimolobos
virgata (Nutt.) O.E. Schulz. Recently, the taxon
has been included in a new genus Transberingia ,
based on analysis of DNA sequences in related
taxa (Price et al. 2001, Al-Shehbaz and O’Kane
2003). Slender mouse-ear-cress is classified by
some taxonomists as a species Transberingia
virgata (Nutt.) N.H. Holmgren (Holmgren
et al. 2005) and by others as a subspecies
Transberingia bursifolia subsp. virgata (Nutt.)
R.A. Price, Al-Shehbaz & O’ Kane (Price et al.
2001).

The new genus Transberingia includes two other
taxa: Halimolobos mollis (Hooker) Rollins from
Alaska, Yukon, Nunavut, Northwest Territories,
and Greenland; and Arabidopsis bursifolia
(de Candolle) Botschantsev from the Russian
Far East. These two taxa are now classified
as one species Transberingia bursifolia (de
Candolle) Al-Shehbaz & O’Kane and also as
one subspecies Transberingia bursifolia subsp.
bursifolia (Al-Shehbaz and O’ Kane 2003, Price
et al. 2001).

The key distinguishing feature that separates
slender mouse-ear-cress from closely related
taxa is the presence of multi-branched
subappressed hairs (trichomes) sometimes
mixed with simple hairs on the upper parts of
the stem and central axis of the inflorescence
(rachis), instead of only sparse simple hairs or
none at all.

The genus Halimolobos has been redefined
based on DNA sequencing to include eight

species in the southwestern United States and
northern and central Mexico, all characterized
by having fruits with large hairs mixed with
smaller ones (Bailey et al. 2007). Slender
mouse-ear-cress and other species in the genus
Transberingia are described as having no hairs
on the fruits, although some recent collections
of slender mouse-ear-cress from Saskatchewan
are reported to have fruits with hairs (C. Neufeld
pers. comm.). More taxonomic investigation
of the prairie population of slender mouse-
ear-cress is suggested to ascertain the degree
to which the population presents distinctive
features when compared to populations of the
same or closely related taxa several hundreds of
kilometres to the southwest and to the north.

Halimolobos virgata continues to be a widely
accepted scientific name by North American
agencies, other organizations and taxonomic
specialists at the time of writing this report
(Integrated Taxonomic Information System
2009). Authors of a key for the Mustard
family (Brassicaceae) being drafted for The
Flora of North America consider the taxon
as Transberingia bursifolia ssp. virgata (Al-
Shehbaz in prep.).

HABITAT

L Habitat Attributes - In Alberta, slender
mouse-ear-cress is found in the Dry Mixedgrass
Natural Subregion of the Grassland Natural
Region (Alberta Natural Heritage Information
Centre [ANHIC] 2005), in the lower South
Saskatchewan River and Red Deer River basins.
The climate is continental, characterized by
extremes in temperatures with warm summers
and cold winters. In the Dry Mixedgrass
Natural Subregion the mean annual temperature
is 4.2°C, the mean July temperature is 18.5°C,
and the mean January temperature is -12.1°C
(Natural Regions Committee 2006). There is an
average of 1 13 frost-free days per year, and the
average number of growing degree days during
the growing season, April through August,
is 1318, the highest of any natural region in

Alberta. Growing degree days is a cumulative
measure of the temperature above 5°C that
indicates energy available for plant growth.
Average annual precipitation is 333 mm; of
that, 241 mm falls during the growing season.
The summer moisture index (degree days
divided by mean precipitation) averages 7.0,
the highest (and hence, driest) of any natural
subregion in Alberta. A summer moisture
index higher than 4.0 indicates that significant
moisture deficits are likely for extended periods
during the growing season (Natural Regions
Committee 2006). High summer temperatures,
low summer precipitation, drying winds, and
intense sunshine contribute to the high moisture
deficits in midsummer. Low winter snowfalls
contribute little to soil moisture reserves.

In Alberta, slender mouse-ear-cress grows on
silty to sandy parent material of glaciofluvial
(deposited by glacial meltwater), fluvial
(deposited by rivers/streams) or eolian
(deposited by wind) origin on undulating to
rolling sandy plain and river valley slopes and
terraces (Bradley 2008). It may occur on sandy
fluvial veneer over moderately calcareous till.
It is reported near, but not in, choppy sand
hills or dunes. Elevation varies from 600 m to
750 m. Habitat is generally described as dry to
mesic.

Slender mouse-ear-cress grows mainly on soils
that are classified as orthic brown chernozems
and are of coarse texture (sandy loams or sands)
in sandy ecological/range sites (Adams et al.
2005). Soil map units in which slender mouse-
ear-cress has been reported include Bingville-
Cavendish (BVCV), Cavendish (CVD),
Vendisant-Cavendish (VSCV), Foremost-
Purple Springs (FMPL) and Pemukan (PUN),
all characterized as coarse-textured fluvial
or fluvial veneer over till (Kjearsgaard and
Pettapiece 1986). One location is in an area
of intersection of a sandy Cavendish-Purple
Springs (CVPL) map unit with a Foremost
(FMT) map unit characterized as medium-
textured, moderately calcareous till. One

location is in a Rough Broken (RBI) map unit
that is undifferentiated parent material of river
valleys.

It is suggested that slender mouse-ear-cress
may be associated with ephemerally wet
depressions and drainages that experience a
slight alkalization of soils (Environment Canada
2009, Smith 1992, C. Bradley pers. obs.). It is
also suggested that at some sites slender mouse-
ear-cress preferentially occurs in the shelter
of shrubs and cacti, perhaps relying on extra
spring moisture from trapped snow (D. Bush
pers. comm.). Small-scale habitat associations
for slender mouse-ear-cress are not well
documented and require further investigation.

Slender mouse-ear-cress usually occurs in native
mixed grassland dominated by needle-and-
thread grass ( Stipa comata). Bare soil without
vegetation is seldom more than 10 percent of
the area of the ecological community. Co-
dominant grasses may include blue grama grass
(Bouteloua gracilis), Sandberg’s bluegrass ( Poa
sandbergii ), June grass (. Koeleria macrantha ),
northern wheatgrass ( Elymus lanceolatus) or
western wheatgrass (. Pascopyrum smithii). Low
sedge ( Carex stenophylla) may also have more
than 10 percent cover. Habitat may include
scattered clumps of sagebrush (Artemesia cana )
and prickly pear cactus ( Opuntia polycantha).

In southwestern Saskatchewan, slender mouse-
ear-cress is found in mixed grassland habitats
similar to those in Alberta (Environment
Canada 2009). In addition to occurring on
chemozemic soils of sandy to loamy texture
on fluvial or eolian deposits, it is reported to
inhabit sites with regosolic soils and lacustrine
deposits. It is most commonly found in
native grassland communities dominated
by June grass, needle-and-thread grass and
wheat grasses, often with some sagebrush
or prickly pear cactus. Slender mouse-ear-
cress is reported to be occasionally associated
with wild rose ( Rosa woodsii), snowberry
(Symphoricarpos occidentalis) and silverberry

( Eleagnus commutata). The non-native
invasives, Kentucky bluegrass {Poa pratensis)
and crested wheatgrass (Agropyron cristatum ),
have been reported at a few sites where slender
mouse-ear-cress is found (Environment Canada
2009). Historically, slender mouse-ear-cress
was reported from “meadows” in the Cypress
Hills in Saskatchewan and Wood Mountain;
however, these occurrences have not been
relocated (ASRD 2005, Environment Canada
2009).

In the United States, sites where slender
mouse-ear-cress has been reported range from
valley bottoms to ridge tops, from 1000 m to
3600 m in elevation (Al-Shehbaz in prep.). In
the Sweetgrass Hills of north-central Montana,
slender mouse-ear cress was found at 1402 m
in grassland dominated by needle-and-thread
grass, western wheatgrass and Idaho fescue
(Festuca idahoensis) on thin soils over glacial
gravels (collection of June 13, 1989 by E.C.
Darfler, Gray Herbarium #246362) (B. Heidel
pers. comm., S. Mincemoyerpers. comm., Gray
Herbarium 2009). In the Tendoy Mountains
of southwest Montana, slender mouse-ear-
cress occurs in open shrublands dominated
by big sagebrush and mountain mahogany on
valley terraces at 1700 m to 2300 m (Montana
Field Guide 2008, University of Montana
Herbarium 2008, R Lesica pers. comm.). In
Wyoming, it is reported mostly in montane
habitats, especially sagebrush communities in
the vicinity of calcareous rock outcrops (ASRD
2005). In northeast Utah, slender mouse-
ear-cress is associated with moist loamy to
gravelly substrates at 2100 m to 2700 m. At
the southwest limit of its range in east-central
California, slender mouse-ear-cress occurs
in “meadows” and seeps in pinyon-juniper
woodland at 2000 m to 3000 m (Calflora 2008,
California Native Plant Society 2008).

2. Habitat Trends - Grasslands are one of
North America’s most threatened ecosystems
(Gauthier et al. 2003). Mixedgrass and
shortgrass prairie have been reduced to

20%-30% of their former extent, the decline
caused primarily by agriculture expansion,
urban development, oil and gas development
and the construction of transportation and
utility corridors. In Alberta, native prairie
is estimated to have declined by 60%-70%
since colonization in the late 1890s (Alberta
Environmental Protection 1997, Alberta
Prairie Conservation Forum 2000). The Dry
Mixedgrass Natural Subregion has a higher
proportion of intact grasslands remaining
(about 55%) than other subregions of the
Grassland Natural Region; however, the extent
to which these are in native condition is not
well documented.

Native prairie continues to decline because of
human activities and the spread of invasive non-
native species in fragmented landscapes. The
energy sector footprint has been increasing at a
rate of about 9000 hectares per year across the
Grassland Natural Region (Prairie Conservation
Forum 2008). A cumulative effects assessment
of a regional study area extending from
Medicine Hat to the Red Deer River and from
the west boundary of the Canadian Forces Base
(CFB) Suffield to Highway 41 estimates bare
ground resulting from agriculture (cultivation)
and industrial development has increased from
10.2 ha/km2 in 1970 to 14.3 ha/km2 in 2005, an
increase of 40% (Environment Canada 2008a).
Linear disturbance has increased from 2.7 km J
km2 to 5.2 km/km2, an increase of 93%, over
the same thirty-five year period. This trend is
expected to continue.

Several major pipelines and gas fields have
been developed over the last decade in native
grasslands within the known provincial range of
slender mouse-ear-cress and more development
is proposed. Gas field development with
densities up to 16 wells per section (6 wells
per km2) has resulted in total disturbed area
of up to 12% and linear disturbance footprint
of up to 12 km/km2 (Smith and Tulis 2007).
The Great Sand Hills Advisory Committee
(2007) considers anthropogenic disturbance

footprint of more than 1 .9 km/km2 to be “highly
developed.”

A modified plant community is associated
with anthropogenic disturbances in mixedgrass
prairie, not only in areas where vegetation
and soil have been directly impacted by the
land use but also indirectly through invasion
of non-native species into adjacent areas of
native vegetation (AXYS 2005, Bradley 2003,
Great Sand Hills Advisory Committee 2007,
Henderson 2007, Rowland 2008, Smith 2007,
Smith and Taylor 2007, Smith and Tulis 2007).
Invasive, non-native species commonly found
in grasslands in southern Alberta include crested
wheatgrass (. Agropyron cristatum), Kentucky
bluegrass ( Poa pratensis ), smooth brome
( Bromus inermis ), downy brome (Bromus
tectorum) and leafy spurge ( Euphorbia esula).
Once established, these invasive species
persist.

Crested wheatgrass establishes in habitats
suitable to slender mouse-ear-cress (Bradley
2008). It is reported to spread by seed into native
grasslands at rates up to 0.8 m/year (Henderson
2007, Henderson and Naeth 2005). Crested
wheatgrass is associated with decreased plant
community diversity, decreased soil organic
matter and reduced carbon sequestration
(Christian and Wilson 1999, Heidinga and
Wilson 2002, Henderson and Naeth 2005,
Jordan et al. 2008).

Leafy spurge also establishes in habitats suitable
to slender mouse-ear-cress (Bradley 2008). It
is reported to spread by seed and roots into
native grasslands at rates of up to one metre
per year (National Park Service 2003). Leafy
spurge outcompetes native species by shading,
usurping available water and nutrients, and
through plant toxins that prevent the growth
of other plants underneath it (National Park
Service 2003).

One location where slender mouse-ear-cress
was reported in 1884 (Medicine Hat [EO

008]) is no longer suitable habitat as a result
of anthropogenic disturbance for municipal
development and establishment of crested wheat
grass. At a location where slender-mouse-ear-
cress was reported in 1 978 (Sandy Point, north of
McNeill [subEO 002]), surveyors undertaking
subsequent searches noted a modified plant
community dominated by crested wheatgrass
(ASRD 2004, Macdonald 2002). Two other
locations where slender mouse-ear-cress has
not been found during surveys within the last
10 years (west of McNeill [EO 005]; north
of Duchess [EO 009]) have experienced
establishment of modified plant communities
as a result of development of a pipeline
corridor, gas wells and access roads (Bradley
2008). Leafy spurge invasion has been noted at
one location of slender mouse-ear-cress (south
of Empress [EO 017]). Long-term impact of
invasive, non-native species on slender mouse-
ear-cress presence is not known (Environment
Canada 2009).

A conclusion from the information provided in
this section is that a large portion of potential
native upland and river valley habitat for slender
mouse-ear-cress has been lost owing to human
activity over the last century. Substantial further
loss is predicted if current trends in land use
and non-native plant species invasion continue
without measures being taken to identify and
protect sites where slender mouse-ear-cress
occurs.

CONSERVATION BIOLOGY

Slender mouse-ear-cress is a biennial or
sometimes short-lived perennial or annual herb
in the mustard family (Brassicaceae) (Kershaw
et al. 2001, Moss 1983). The plant is tap-
rooted and rosette-forming with one to several
erect, simple or branched stems 10 cm-40 cm
tall. Plants vary greatly in stature, from tall,
branched and robust to short, single-stemmed
and thin. A feature that distinguishes slender
mouse-ear-cress from mustards of similar
appearance, including Arabis hirsuta and

Erysimum inconspicuum , is that the upper stem
generally has longer straight, simple or forked
hairs (trichomes) mixed with shorter, freely
branching hairs. Leaves of the basal rosette are
up to 6 cm long and 15 mm wide, tapered to
the stalk and wavy-toothed. Stem leaves are
smaller, the upper leaves stalkless and clasping
with small basal lobes (auricles). Numerous
small flowers, about 4 mm-8 mm across, occur
on stalks clustered at the tip of the stem. Each
flower has four white petals and four hairy
sepals. The flowering stem (a raceme) elongates
in fruit such that the linear pods (siliques) are
erect and borne on stalks 7 mm-1 1 mm long
that usually extend at a 45 degree angle from
the stem. Pods are 2 cm-4 cm long and 1 mm
wide, generally hairless and cylindrical. Seeds
are crowded in two irregular rows in each of
two locules.

Other mustards of similar appearance occurring
in habitat similar to slender mouse-ear-cress
can be distinguished in fruit by having flattened
pods (Arabis holboellii var. retrofracta, Arabis
divaricarpa, Arabis hirsuta) or four-angled
pods with a beak and seeds in one row in each
locule (Erysimum spp.). Stems of Erysimum
spp. have only simple or forked (malpighian)
hairs, often dense, and lack the scattered,
shorter freely-branching hairs characteristic of
slender mouse-ear-cress.

In Alberta, slender mouse-ear cress has been
reported bearing flowers and immature fruit
during mid-May to late June and bearing
mature fruit and dispersing seed during late
June to mid- July (ASRD 2005, ANHIC 2008,
B. Smith pers. comm.). Each stem bears up to
two dozen flowers and each linear pod contains
a few dozen seeds; therefore, individual plants
on average likely produce between 100 and
400 seeds (ASRD 2005). Further study would
be required to determine whether pollination
in slender mouse-ear-cress is wind- or insect-
mediated, and whether self-fertilization occurs.
Seeds are small (<1 mm) and wingless, with a
seed coat that is minutely reticulate. The pods

split open at maturity while still attached to
the plant, readily dispersing the seeds, most of
which likely fall near the parent plant, although
some may be carried farther by wind, water
or animals. Leaves rapidly dry up, stems
turn brittle and do not appear to persist long
after seed dispersal (C. Bradley pers. obs., C.
Neufeld pers. comm.).

There is no information on seed longevity, the
rates of seed germination, or survival rates of
seedlings for slender mouse-ear-cress. The first
year following seed germination, a tap root and
rosette of leaves may grow. A flowering stem is
generally produced in one or more subsequent
years. Little information is available on how
long individual plants live. For many years
slender mouse-ear-cress was described as
biennial, occasionally annual (Moss 1983);
however, more recent taxonomic treatments
consider it a perennial, perhaps short-lived
(Price et al. 2001).

There is evidence that the number of plants at
one location may fluctuate substantially from
year to year, suggesting that local weather
conditions influence seed production, seed
germination and plant growth. Slender mouse-
ear-cress may be associated with habitats that
are wet in the spring (Environment Canada
2009). Lower than average precipitation in
a given year may suppress germination and
growth, resulting in underestimation of size
and extent of a population. Therefore, surveys
are best planned for years when there is above
average precipitation during April, May and
June.

Slender mouse-ear-cress appears to be tolerant
of light to moderate livestock grazing pressure.
It does not appear to be preferentially selected
by grazers and may be avoided. It is classified
as tolerant of heavy grazing pressure in
range surveys in Wyoming (ASRD 2005). In
locations with heavy livestock use, slender
mouse-ear-cress is generally found close
to shrubs and cacti, suggesting these plants

shelter it from grazing and trampling (D. Bush
pers. comm.). Slender mouse-ear-cress is not
obviously a disturbance-dependent species,
although small disturbances, such as the action
of hoofs exposing bare soil or creating moist
depressions may provide suitable microhabitats
for its establishment. Periodic fire may also
benefit slender mouse-ear-cress by releasing
nutrients and removing competition of grasses
and shrubs.

DISTRIBUTION

1 . Alberta - All reports of slender mouse-ear-
cress in Alberta are within the Dry Mixedgrass
Natural Subregion of the Grassland Natural
Region, and more specifically, in the watersheds
of the Red Deer River below Drumheller and
the South Saskatchewan River below Medicine
Hat (Figure 1). Occurrences are concentrated
in the Bindloss Plain Ecodistrict (Adams et
al. 2005). This Ecodistrict is characterized as
having surficial materials predominantly of
glaciofluvial and eolian origin and the highest
annual moisture index (ratio of total annual
degree days to total annual precipitation) in the
Dry Mixedgrass Natural Subregion.

Fourteen occurrences or subpopulations make
up the known population of slender mouse-
ear-cress in Alberta, as of January 2009. These
element occurrences are listed in Table 1 and
mapped in Figure 1. Where information on
genetics and propagule dispersal is lacking,
element occurrences are defined as separate
populations no less than 1 km apart if
intervening habitat conditions are unsuitable,
and no more than 3 km apart if intervening
habitat conditions are suitable for the species
(NatureServe 2004). Of the fourteen slender
mouse-ear-cress occurrences in Alberta, one
is considered extirpated, one is considered
historical, three are considered failed-to-find
and nine are considered extant (ANHIC 2008,
Hammerson et al. 2008).

Figure 1: Occurrence record locations for slender mouse-ear-cress in Alberta. See Table 1 for
information on each record. Occurrence numbers are assigned by the Alberta Natural Heritage
Information Centre.

The first collection of slender mouse-ear-cress
in Alberta was made in 1894 by John Macoun
near the police barracks at Medicine Hat,
known as Police Point (EO 008 in Table 1). The
collection is filed with the Canadian Museum of
Nature National Herbarium. This occurrence
is considered extirpated because substantial
habitat alteration has occurred as a result of
municipal development, and slender mouse-
ear-cress has not been found during subsequent
rare plant surveys in and near Medicine Hat. A

second collection by John Macoun, generally
described as from the Cypress Hills, has been
determined to be likely from Saskatchewan and
not Alberta (ASRD 2005).

The second collection of slender mouse-ear-
cress was made in 1914 by M.E. Moodie in
“the vicinity of Rosedale in prairies north of the
Red Deer Valley at 2200-2500 ft on damp soil
near sloughs” (EO 033 in Table 1) (Al-Shehbaz
pers. comm.). The collection, only recently

Table 1: Summary of data on number of plants for occurrences/subpopulations of slender
mouse-ear-cress in Alberta. Data are from the Alberta Natural Heritage Information
Centre (ANHIC) database of rare plant occurrences; element occurrence (EO) numbers
and ranks are assigned by ANHIC. See Figure 1 for occurrence locations. EO Rank: H =
historical; F = failed-to-find; E = extant; X = extirpated. N/a indicates that data are not
available.

Site Name

EO#

(sub)

Rank

Max.

Recorded
Pop. (Year)

Survey Date(s)

Population

Estimate1

Area

(m2)

Rosedale

033

>1 (1915)

1915-06-05

n/a

Duchess Pasture:

009

49 (1997)

1997-06-02

Matzhiwin Creek

2002-xx-xx

2005-05-20

2008-06-16

W of Remount Pasture;

N Boundary CFB Suffield

015

47 (2008)

2008-07-02

300

Cavendish:

Remount Pasture NW

018

87 (2008)

2008-07-05

600

Remount Pasture S;

007

398 (2004)

1997-05-31

N Boundary CFB Suffield

2002-xx-xx

2004-06-07

398

1200

2008-07-02

400

Remount Pasture SE;

003

919 (2004)

1997-05-30

900

1997-05-30

200

1500

2002-xx-xx

2004-06-26

919

1000

Bindloss SW;

029

96 (2007)

2007-05-29

n/a

Remount Pasture NE

2008-06-06

160

Bindloss W;

030

130 (2007)

2007-05-27

T —

n/a

Minor Ranch

2008-06-13

Empress S;

Big Loop S. Sk. R.

016

7 (2008)

2008-07-03

Empress;

Big Loop S. Sk. R.

017

15(2008)

2008-07-03

Linstead Flats;

001

20 (1995)

1995-06-23

375

CFB Suffield National Wildlife

2004-xx-xx

Area

2005-06-26

S Sk. R. pipeline crossing;

005

>100 (1997)

1997-05-29

>100

200

W of McNeill

2002-xx-xx

2004-xx-xx

Table 1 continued.

Site Name

EO#

(sub)

Rank

Max.

Recorded
Pop. (Year)

Survey Date(s)

Population

Estimate1

Area

(m2)

McNeill N

01 02

251(2007)

1997-05-24

200

1997-05-24

1999-07-12

200

2002-xx-xx

2004-06-06

145

100

2004-06-24

2004-09-14

n/a

2007-07-01

n/a

2007-07-02

n/a

2007-07-02

n/a

2007-07-02

150

250

2007-07-02

n/a

2007-07-27

1114

2007-07-27

n/a

2007-07-27

2008-06-15

400

2008-06-15

n/a

2008-07-01

n/a

2008-07-02

(McNeill N, Sandy Point;
Hwy 41 at S. Sk. R.)

(002)2

(F)

>1(1978) 1978-05-16

n/a

1991-06-07

1997-05-24

2002-xx-xx

2003-xx-xx

Police Point;

008

>1 (1884) 1884-05-31

n/a

Medicine Hat

1991-06-07

2002-xx-xx

1 Population estimate is the number of individuals counted in a cluster or several clusters, as
reported to ANHIC. Multiple (sub)population estimates on the same date apply to different plant
clusters within the same subpopulation.

2 Sub EO 002 has recently been included in EO 010 and is not shown on the map in Figure 1. For
three decades it was considered a separate EO, and is the only known site within the
subpopulation located west of the river.

relocated, is filed with the Missouri Botanical
Garden (Moodie #949). This occurrence is
considered historical, since slender mouse-ear-
cress has not been reported from the vicinity
in several decades (ANHIC 2008); however,
targeted search in the vicinity has yet to be
conducted.

Six decades elapsed before slender mouse-
ear-cress was collected again, in 1978 by John
Hudson at Sandy Point north and east of the
Highway 41 Bridge in the South Saskatchewan
River valley (EO 010, subEO 002; Table 1). A
collection (#335977) is filed at the Agriculture
Canada Herbarium in Ottawa. In four separate
searches since 1991, surveyors have failed to

find slender mouse-ear-cress on the terraces
where the collection was made, noting
considerable invasion by crested wheatgrass
(ASRD 2004, Macdonald 2002, Smith 1992
and 2000). This location is now considered
part of a larger element occurrence extending
to the east and south (EO 010).

In 1995, slender mouse-ear-cress was collected
in upland sand plain habitat during an inventory
of vascular plants in the Canadian Forces Base
Suffield National Wildlife Area (EO 00 1 ; Table
1) (Macdonald 1997). Collections are filed
with the University of Calgary herbarium and
the Provincial Museum in Edmonton (B95.9.6).
Surveyors failed to find plants during searches
at this location, near Linstead Flats, in 2004 and
2005 (Elchuk 2005); hence, this occurrence is
considered failed-to-find.

In 1997, seven new upland occurrences of
slender mouse-ear-cress (EO 003, EO 005,
EO 006, EO 007, EO 009, EO 010 and EO
032; see Table 1) were reported during a rare
plant survey along a proposed pipeline route
between the Alberta/Saskatchewan border near
McNeill and westward to beyond Matzhiwin
Creek near Duchess (Smith 2000). Locations
were identified as distances along the pipeline
and legal land descriptions (section/township/
range), and not by more precise GPS coordinates
(B. Smith pers. comm.). Population size
included counts of plants of the current year
and also counts of plants identified as “old
stems” from the previous year. Three Alberta
collections of Halimolobos virgata and one
Saskatchewan collection filed at the University
of Calgary herbarium included dried-up stems
and remnants of pods from the previous year that
have been re-identified as Erysimum spp. (C.
Bradley pers. obs., I. Macdonald pers. comm.,
B. Smith pers. comm). All element occurrences
documented by B. Smith included plants of the
current year except the two element occurrences
in the Buffalo Atlee Pasture that were recorded
solely on the basis of “old stems” (EO 006 and
EO 032). These two element occurrences were

recorded as “invalid identification” in 2009 (T.
Kemper pers. comm.), and are therefore not
included in Table 1 or Figure 1. Four Alberta
collections of slender mouse-ear-cress from
locations identified in the 1997 survey are filed
at the University of Calgary herbarium: Duchess
Pasture EO 009 (UAC 56451) Remount Pasture
003 EO (UAC 56455) and near McNeill EO
010 (UAC 56454 , UAC 56457).

Several subsequent intense and targeted
searches between 1997 and 2008 resulted in
confirmation of the presence of slender mouse-
ear-cress at three locations, two in the Remount
Pasture and one near McNeill (EO 003, EO
007 and EO 010) and failure to find it at four
locations (EO 005, EO 009, EO 006 and EO
032; the latter two were subsequently found
to be invalid, as described above). Additional
surveys are needed to determine with confidence
if slender mouse-ear-cress is extirpated at the
two occurrences where surveyors have failed to
find previously reported populations in over a
decade — the Duchess Pasture near Matzhiwin
Creek (EO 009) and the pipeline corridor
crossing of the South Saskatchewan River (EO
005). Alteration of native plant communities
because of major pipeline corridor construction
and gas field development may be contributing
to the plant’s absence.

In 2007, during rare plant survey along a
proposed pipeline route from Hardisty south
through McNeill and eastward, slender mouse-
ear-cress was found at two new locations south
of the Red Deer River near Bindloss (EO
029 and EO 030; Table 1). The extent of the
subpopulation near McNeill (EO 010) was
extended northward to the proposed pipeline
crossing of the South Saskatchewan River
about 7 km downstream of Sandy Point, based
on several new reports during the 2007 and
2008 surveys (D. Bush pers. comm., C. Tannas
pers. comm., A. Lees pers. comm.).

In 2008, four new occurrences of slender
mouse-ear-cress were reported during a targeted

survey in apparently suitable habitat (Bradley
2008). One of these new occurrences is along
the northern boundary of CFB Suffield, a few
kilometres west of the Remount Pasture (EO
018; Table 1). Another occurrence is a few
kilometres south of the Red Deer River between
Cavendish and Buffalo (EO 015; Table 1),
and two others are about 5 km apart south of
Empress and west of the South Saskatchewan
River where it loops into Saskatchewan (EO
016 and EO 017; Table 1).

Over the last few decades, several rare plant
surveys have not reported any occurrences of
slender mouse-ear-cress in apparently suitable
sand plain and river valley habitat in Alberta.
Slender mouse-ear-cress was not found in
extensive survey of sand hill and sand plain
habitats of southern Alberta in 1987 (Wallis and
Wershler 1988). Neither was it found during
more recent rare plant surveys within the CFB
Suffield National Wildlife Area (Elchuk 2005),
the Onefour Research Station (Bradley et al.
2006), the Many Island Lake area (C. Wallis
pers. comm.) and public lands leased to the
Drowning Ford Grazing Association and
Hargraves Ranch (J. Lancaster pers. comm.).
During the last 10 years, rare plant surveys
in other sand plain habitats of southeast
Alberta conducted as part of environmental
assessments for proposed pipeline routes or
gas field developments have resulted in few,
if any, reports of slender mouse-ear-cress,
even though the considerable search effort was
targeted towards slender mouse-ear-cress and
other priority species at risk (ASRD 2004 and
2008, J. Lancaster pers. comm., D. Bush pers.
comm.). In addition, systematic and intensive
search effort in 2008 specifically of habitat
considered to have high potential for slender
mouse-ear-cress, resulted in no occurrences
in 14 of 18 quarter sections searched using
parallel, randomly spaced transects (Bradley
2008).

The extent of occurrence of slender mouse-
ear-cress is the area within a polygon made

by drawing straight lines between the most
northerly, westerly, southerly and easterly
occurrences. A polygon that encompasses
only occurrences ranked as extant, including
mostly sand plain and choppy sand hills, is
about 530 km2 in area (G. Berg pers. comm.).
This area increases to 2930 km2 when all
occurrences considered extant or failed-to-find
are included, and 9998 km2 when all reported
occurrences in Alberta (even those ranked as
extirpated or historical) are included (G. Berg
pers. comm.). At least half of the habitat within
the extant range (530 km2) of slender mouse-
ear-cress in Alberta has been converted to non-
native vegetation and a considerable portion
of the native habitat is unsuitable including
shrublands, wetlands and alkaline flats, till
ridges, rolling sand dunes, eroding slopes and
rivers or streams. A similar proportion of the
range that includes all reported occurrences
(9998 km2) is unsuitable for slender mouse-
ear-cress.

The known area of occupancy, defined as
the area within the extent of occurrence
occupied by slender mouse-ear-cress excluding
unsuitable or unoccupied habitat (IUCN 2001),
is estimated to be less than 0.05 km2 using data
from Alberta Natural Heritage Information
Centre (ANHIC) occurrence records. There are
33 unique locations of slender mouse-ear-cress
in ANHIC reports (based on UTM coordinates)
and the maximum population extent for any
one location is 1500 m2 (Table 1), implying
that area of occupancy for all known locations
is unlikely to exceed 0.05 km2 (33 x 1500 m2).
Slender mouse-ear-cress plants are found in
small discrete patches and seeds appear to fall
close to the parent plants; hence area between
patches is considered to be unoccupied.

Potential area of occupancy may also be
estimated to be less than 0.05 km2 if one applies
the percentage area of suitable habitat occupied
by slender mouse-ear-cress, derived from
results of the systematic 2008 survey, over the
total extent of extant occurrences (530 km2).

Eighteen quarter sections with apparently
suitable habitat were surveyed along up to ten
randomly-spaced, parallel transects in each
quarter section (Bradley 2008). The sampling
approach gives an 80% to 90% probability of
detection, assuming an area of occupancy of
0.1% of the study area (D. Henderson pers.
comm.). The total area occupied by the four
populations found in 2008 was 920 m2 out of
a total search area of approximately 11.5 km2;
hence, only about 0.01% of apparently suitable
habitat searched was found to be occupied by
slender mouse-ear-cress.

The area of occupancy calculated by summing
occupied 1 -km x 1 -km squares (excluding failed-
to-find, extirpated and historical occurrences)
results in an area of 18 km2 (or 52 km2 using
2-km x 2-km squares, the International Union
for Conservation of Nature standard [IUCN
2001] but less biologically relevant for this
species).

2. Other Areas - In Saskatchewan, slender
mouse-ear-cress is known from 13 locations,
plus three additional historical locations that
have not been relocated (C. Neufeld pers.
comm.) (Figure 2). Historical locations include
one in Wood Mountain and two in the Cypress
Hills. Extant populations occur north and west
of the South Saskatchewan River between
Riverhurst and Outlook (Riverhurst, Birsay,
Macrorie, Coteau, Lucky Lake), northeast of
Kindersley (Stranraer), near Estuary on the
South Saskatchewan River (Estuary, Alkali
Creek) and in the Great Sand Hills (Golden
Prairie, East Fox, Liebenthal). The closest
known location to Alberta is within the Prairie
National Wildlife Area Unit 20, approximately
45 km directly east of Alberta’s McNeill
location. Native prairie on sand plain contiguous
with known habitat for slender mouse-ear-cress
near McNeill appears to extend 10-15 km into
Saskatchewan; however, survey for slender
mouse-ear-cress has not yet been conducted in
this area (C. Neufeld pers. comm.).

In Montana, slender mouse-ear-cress was found
in 1 989 in the East Butte uplift of the Sweetgrass
Hills (SE6-36-5 E 5M), approximately 3 km
north/northeast of the summit of Mount
Brown and about 10 km south of the border
with Alberta (Gray Herbarium 2009, Westech
1989). This is within Liberty County about
200 km south of McNeill. Collections from
Sheridan and Phillips counties in northeastern
Montana originally identified as Halimolobos
virgata have been re-identified as Arabis hirsuta
(University of Montana Herbarium 2008). All
other known Montana locations of slender
mouse-ear-cress are a further 450 km south in
the Tendoy Mountains of Beaverhead County
in the southwest part of the state (P. Lesica pers.
comm.). The nearest population in Wyoming
is also 450 km south of the Sweetgrass Hills
in the Absaroka Range of the northwest part of
the state (University of Wyoming 1998).

Elsewhere in the United States, slender mouse-
ear-cress is known from northeastern Idaho
(Butte county), central and western Wyoming
(several counties), central Colorado (Gunnison
and Park counties), northeastern Utah (Dagget
and Wasatch counties), southwest Nevada
(Esmeralda and Nye counties) and east
central California (Inyo and Mono counties)
(NatureServe 2009, Al-Shehbaz in prep.)
(Figure 2).

POPULATION SIZE AND TRENDS

1. Alberta - There are insufficient data to
confidently estimate the size of the provincial
population of slender mouse-ear-cress, in terms
of number of individuals. Survey methods used
in acquiring existing data are generally not
well defined and likely vary greatly, thereby
confounding meaningful comparisons among
locations and years. With these provisos, a
population size of 3000-7000 individuals
is estimated based on the data currently
available.

Figure 2: Distribution of slender mouse-ear-cress in North America (based on information available
from NatureServe 2009).

For slender mouse-ear-cress, an individual is
defined by a basal leaf rosette. Reproductive
plants will have a flowering shoot or stem
associated with a basal rosette, whereas non-
reproductive plants will not. In addition, viable
seeds in the soil are part of the non-reproductive
population but are not readily counted. The
most practical and efficient unit for monitoring
population size of slender mouse-ear-cress is
the flowering shoot (Henderson 2008).

The number of reproductive individuals within
a subpopulation, as variously defined in reports
filed with ANHIC, ranges from 1 to 919 (Table
1, ANHIC 2008). The distribution of plants
within known subpopulations (separated by no
more than 3 km) varies from one small cluster
of one or a few individuals to several scattered
clusters of several to many individuals. The
three largest known subpopulations, in terms of
extent and size, are one north of McNeill and
east of the South Saskatchewan River (EO 010)
and two along the northeast boundary of CFB
Suffield in the Remount Pasture (EO 003 and
EO 007).

There are more data for the McNeill
subpopulation than any other subpopulation
(EO 010, Table 1). Data consist of reports of
slender mouse-ear cress at approximately 20
unique sites (based on GPS coordinates provided
by surveyors) over 1 1 years (1997-2008) (Table
1), in an area approximately 10 km by 3 km
(30 km2) east of the South Saskatchewan River
to the Alberta-Saskatchewan border. Most of
the survey effort has been focused along two
proposed pipeline rights-of-way and has not
included a systematic approach to estimating
total population size. Reported plant clusters
range in size from 1 individual to 1 50 individuals
and in density from 36 individuals in 1114 m2
(0.03 plants/m2) to 39 individuals in 10 m2
(3.9 plants/m2). The population size also varies
over time. During a spring survey in 1997, 104
individuals were reported in three clusters; in
1999, only 12 individuals were reported at the
same sites; in 2002, no individuals were found;

and, in 2004, 1 84 individuals were reported in
two clusters. In 2007, 251 individuals were
reported in 1 1 clusters throughout a larger area
compared to previous surveys. From these
data one can estimate there are several hundred
(300-700) reproducing individuals in the
McNeill subpopulation in a year with suitable
conditions for germination and growth, and
there are large fluctuations in the number of
reproducing individuals from year to year.

Data on the two southern Remount Pasture
subpopulations (EO 003 and EO 007), along the
boundary with CFB Suffield, consist of three to
four records at each location (Table 1). Reports
of size for the most easterly subpopulation (EO
003) are, in 1997, 216 individuals in three
clusters; in 2002, no individuals; and, in 2004,
9 1 9 individuals in 1 000 m2. Reported clusters
are scattered over a 3 -km distance, east to west.
Reports of size for the second subpopulation
(EO 007) are, in 1997 and 2002, no individuals;
in 2007, 398 individuals in 1200 m2; and, in
2008, 25 individuals in 400 m2. From these data
we can conclude that there are several hundred
(300-700) individuals in each of the two
Remount Pasture subpopulations, and perhaps
a few thousand (1000-3000) individuals in a
year with suitable conditions for germination
and growth. As well, there is evidence for
large fluctuations in the number of reproducing
individuals from year to year. These two
subpopulations are separated by approximately
3 km; however, the intervening habitat is
native grassland on sandy parent material
and additional survey may determine that the
two subpopulations are one. Suitable habitat
for slender mouse-ear-cress also occurs a few
hundred metres south of these subpopulations
within CFB Suffield; however, a major pipeline
corridor, vehicle trail, fenceline and road bisect
what once was contiguous habitat.

Another subpopulation (EO 015) of slender
mouse-ear-cress along the north boundary of
CFB Suffield and west of the Remount Pasture
is separated from the nearest subpopulation

(EO 007) by five kilometres and a till ridge. In
2008, the only year of record, the subpopulation
was reported to have 47 individuals in 300 m2.

Two subpopulations (EO 029 andEO 030) about
1 5 km north ofCFB Suffield’s northern boundary
near Bindloss have reported maximums of 130
and 96 individuals, respectively, in 2007, and
much reduced numbers in 2008. These two
subpopulations are separated by 3 km, including
a broad corridor of disturbance resulting
from railway line and highway construction;
hence there is unlikely to be sufficient genetic
exchange between these two subpopulations to
consider them one. In 2008, about 15 km to
the west along Highway 555 near Cavendish,
another subpopulation (EO 018) was reported
to have 87 individuals in a 600 m2 area.

A subpopulation (EO 005) of about 100
individuals scattered in small clusters of 3-7
stems over an area of about 200 m2 was reported
in 1997. This subpopulation occurs on upland
grassland west of the South Saskatchewan
River near where a pipeline corridor crosses
the river about 12 km upstream of the Highway
41 bridge (Smith 2000, Smith pers. comm.). It
is about 8 km west of McNeill and about 8 km
east of the CFB Suffield’s eastern boundary.
Two subsequent searches in the area failed to
find slender mouse-ear-cress.

Three subpopulations are reported to have
fewer than 20 individuals. A subpopulation
(EO 001) in CFB Suffield about 20 km south of
the northern boundary was reported, in 1995, to
have 20 individuals in 375 m2. No individuals
have been found there in two subsequent
surveys. Two subpopulations (EO 016 and EO
017) south of Empress are reported, in 2008,
to have only 7 and 1 5 reproducing individuals,
respectively, and are separated by 5 km. The
intervening habitat is native grassland on sandy
substrate; hence, additional search effort may
find these two subpopulations to be one.

The disjunct subpopulation (EO 009) near
Matzhiwin Creek north of Duchess was
characterized as having 54 individuals in
“several small patches over 2 km” when first
found in 1997 (Smith 2000). No slender mouse-
ear-cress has since been found during several
searches at this location. This subpopulation
is separated by over 160 km from the nearest
subpopulations in the Remount Pasture. Much
of the intervening area is considered unsuitable
habitat for slender mouse-ear-cress, given that
surficial deposits are not fluvial-eolian sands but
rather till, lacustrine silts and clays and eroded
bedrock of the Dinosaur badlands (Kjearsgaard
and Pettapiece 1986).

Based on the data available, the provincial
population of slender mouse-ear-cress is
estimated to be in the order of several thousands
(3000-7000) of reproducing individuals in years
when conditions are suitable for germination
and growth. To accurately define population
size and trends, known locations would need
to be surveyed over a period of several years
using a well-defined monitoring protocol
designed to meet a specified degree of statistical
confidence with respect to population size and
extent (Elzinga et al. 1998, Henderson 2008).
As well, a systematic approach to searching for
additional subpopulations would be required.
Environmental stochasticity and observation
error pose challenges, as does the invisibility
of the seed bank (Brigham and Thomson 2003,
Elderd et al. 2003, Alexander et al. 2009).

2. Other Areas - In Saskatchewan, the
maximum population of slender mouse-ear-
cress recorded at one of the 13 extant locations
is 3678 individuals; four subpopulations are
reported to have 100-150 individuals; three
have 20-40 individuals; three have fewer than
five individuals; and, two lack count data with
no plants found in recent survey (C. Neufeld
pers. comm., Environment Canada 2009).
More systematic surveys for slender mouse-
ear-cress in the Great Sand Hills in 2006, 2007
and 2008 are providing baseline data for more

confidently estimating population size and
monitoring long-term trends.

No information is available on population
size of slender mouse-ear-cress in the United
States.

LIMITING FACTORS

Limiting factors are major factors that affect
habitat quality and availability, reproductive
output, or survival of individuals. The focus
is on factors that have an anthropogenic
origin. The effects of limiting factors may be
cumulative.

7. Loss and Degradation of Habitat - Loss of
native grasslands within the range of slender
mouse-ear-cress continues to affect habitat
quality and availability. Native prairie decline
is caused primarily by agriculture expansion,
urban development, oil and gas development
and the construction of transportation and utility
corridors, as well as the spread of invasive
non-native species in fragmented landscapes.
Information on loss of native grasslands within
slender mouse-ear-cress range is provided in
the Habitat section of this report. Key points
are summarized as follows:

• Over the last century, approximately
50% of the Dry Mixedgrass Natural Subregion
in southeast Alberta has been converted from
native vegetation to a completely altered state
by human land uses (Alberta Environmental
Protection 1997).

• Since 1970, in a study area that
encompasses all of the provincial range of
extant slender mouse-ear-cress subpopulations,
bare ground resulting from agriculture
(cultivation) and industrial development has
increased 40% (from 10.2 ha/km2 to 14.3 ha/
km2) (Environment Canada 2008a). In the
same period linear disturbance has increased
93% (from 2.7 km/km2 to 5.2 km/km2).

• A subpopulation (EO 008) of slender
mouse-ear-cress has been extirpated as a result
of municipal development.

• Habitat for eight subpopulations of
slender mouse-ear-cress has been altered
within the last few decades by gas field and
major pipeline corridor development (EO 009,
EO 015, EO 007, EO 003, EO 029, EO 030, EO
005, EO 010).

• As the amount of anthropogenic edge
in native prairie increases, the potential for
invasion of non-native species increases.
Invasion of non-native species, especially
crested wheat grass, from human disturbances
is adversely affecting the quality of slender
mouse-ear-cress habitat.

Further loss or alteration of habitat for slender
mouse-ear-cress is predicted if current trends in
land use continue.

Recently, the Joint Review Panel of the
Canadian Environmental Assessment Agency
and the Energy Resources Conservation Board
recommended developing a management
strategy for non-native invasive plant species
to protect native prairie integrity in the Suffield
National Wildlife Area (Joint Review Panel
2009). The National Wildlife Area includes
known habitat for slender mouse-ear-cress.
The Joint Review Panel also recommended
excluding industrial disturbance in critical
habitat for slender mouse-ear-cress unless
otherwise specifically permitted.

2. Anthropogenic Climate Change - Population
data suggest that annual weather influences
germination and growth of slender mouse-ear-
cress. For example, the absence of slender
mouse-ear-cress rosettes and stems in 2002
at locations where previously there had been
many individuals may be explained by lower
than average precipitation in May 2002; less
than 10 mm measured at Empress and Bindloss
compared to an average of 40 mm (Environment
Canada 2008b). Relatively high numbers of
individuals found in 2007 may be explained by
higher than average precipitation in May 2007;
57 mm measured at Bindloss (Empress data not
available). It can be assumed that predicted

change in climate because of human activities
will affect slender mouse-ear-cress reproduction
and survival, as well as its habitat.

Slender mouse-ear-cress occurs in that part of
Alberta with the highest potential for significant
moisture deficits during the growing season,
that is the Bindloss Plain Ecodistrict of the Dry
Mixedgrass Natural Subregion. Predictions
are that this area will experience up to a 4°C
increase in mean annual temperature by the
2020s, mostly occurring in winter and spring,
and up to a 20% increase in mean annual
precipitation mostly occurring in winter and
spring (Sauchyn and Kulshreshtha 2007);
however, summers will be especially dry. A
trend of increased aridity will most likely be
realized through a greater frequency of dry
years. Also predicted are increased climate
variability and more frequent extreme events,
including a greater frequency of flooding and
severe drought.

Higher precipitation in spring may increase
germination and growth of slender mouse-ear-
cress, especially if the species is associated with
vernal pools, although this has not yet been
confirmed. Increased summer drought may
negatively affect seed viability and survival of
plants that only appear as rosettes in a given
year. The prairie population of slender mouse-
ear-cress in Alberta and Saskatchewan has
survived drought in the past, including that of
the 1930s. However, occurrences in the United
States (where most of the species’ range is) are
at considerably higher elevations, 1000 m-
3600 m, compared to elevations of 600 m-
750 m in Canada, suggesting an affinity to
cooler and moister growing season conditions
than are predicted for the mixedgrass prairie
region with climate change.

Movement of slender mouse-ear-cress
northward as vegetation shifts in response
to climate change may be restricted by lack
of contiguous corridors and blocks of native
mixedgrass prairie on sandy substrates.

3. Altered Fire Regime - Absence of fire
may be affecting the slender mouse-ear-cress
population in Alberta. For millennia, fire
started by lightning or humans was a constant
presence in mixedgrass prairie, fluctuating with
regional climate change, vegetation change, and
cultural change. Fires ranged in size from less
than a hectare to several thousand hectares and
had return intervals from 0-35 years with mean
intervals of 4-10 years (Henderson 2006). Fire
helped to maintain a shifting mosaic of large
ungulate grazing pressure on the landscape and
played a role in soil organic matter formation.

Such a pervasive disturbance in the ecosystem
likely influenced the evolution and distribution
of slender mouse-ear-cress. Fire may affect
these and other herbaceous plants by reducing
competition from perennial grasses and
shrubs for space and resources, stimulating or
suppressing seed germination and sprouting of
dormant roots, enhancing growth by increasing
organic matter in the soil, or directly killing
rosettes and reproductive shoots.

Today, fire suppression is practiced throughout
the range of slender mouse-ear-cress. Alteration
of the fire regime, beyond the range of natural
variation in fire as an ecosystem process, is
likely resulting in more vegetation and litter
cover and less bare soil in the mixedgrass
prairie habitats of slender mouse-ear-cress.
The implications for this species are unknown.

Recently the Joint Review Panel of the
Canadian Environmental Assessment Agency
and the Energy Resources Conservation Board
recommended take measures “that are necessary
and safe” to restore the natural fire regime to
the Suffield National Wildlife Area, which
includes known habitat for slender mouse-ear-
cress (Joint Review Panel 2009).

4 . Altered Grazing Regime - For millennia,
grazing by herbivores such as bison, pronghorn,
elk, deer, small mammals and insects was a
constant presence in the prairie habitats of

slender mouse-ear-cress. Size, shape, spatial
distribution and the succession in grazed
patches varied across the landscape over time,
depending on when, how long, how often and
how intensively the mix of native herbivores
grazed. Environmental modifications brought
about by grazing animals contribute to variety
in habitats and biodiversity in the landscape
(Romo 2007).

Such a pervasive disturbance in the ecosystem
likely influenced the evolution and distribution
of slender mouse-ear-cress. Grazing may affect
herbaceous plants such as slender mouse-ear-
cress by reducing competition from perennial
grasses and shrubs for space and resources,
creating openings that stimulate or suppress
seed germination and sprouting of dormant
roots, enhancing growth by increasing nutrients
in the soil, suppressing growth through soil
compaction, dispersing seed, or directly killing
rosettes and reproductive shoots through
browsing and trampling. Today, slender mouse-
ear-cress is found in areas that receive light to
moderate livestock grazing pressure.

In the 1800s, introduction of cattle meant going
from an open system, where grazing patterns
were climatically defined, to a closed system
where management dictates pattern, timing
and intensity of grazing. The implications
for slender mouse-ear-cress of this altered
grazing regime, beyond the range of natural
variation in grazing as an ecosystem process,
are unknown.

STATUS DESIGNATIONS*

1. Alberta - The evaluation of a detailed status
report for slender mouse-ear-cress (ASRD
2005) under the provincial Species At Risk
Program resulted in an assessment of Data
Deficient in 2005 (Alberta Endangered Species
Conservation Committee Scientific Sub-

* See Appendix 1 for definitions of selected status
designations.

committee 2005). Slender mouse-ear-cress is
considered May Be At Risk according to the
general status review (ASRD 2007). It is also
currently ranked as S1S2 in Alberta (Gould
2006).

2, Other areas - Based on an assessment
by COSEWIC, slender mouse-ear-cress
was designated Endangered in Canada in
April 1992. Its status was re-evaluated and
designated Threatened in Canada in May
2000 (Environment Canada 2009). It is
listed on Schedule 1 of the federal Species at
Risk Act (Government of Canada 2008). In
Saskatchewan, slender mouse-ear-cress is
ranked as S 1 and is listed as Threatened under
the province’s Wildlife Act (Government of
Saskatchewan 2008). Nationally, in Canada
slender mouse-ear-cress has a rank of N2
(NatureServe 2009). A draft recovery strategy
for slender mouse-ear-cress in Canada has
recently been developed (Environment Canada
2009).

In the United States, known locations of slender
mouse-ear-cress are limited to one or a few
counties within each of the states in which it
occurs (except for Wyoming). Slender mouse-
ear-cress is ranked as S 1 in Utah, California and
Colorado, S3 in Montana and Wyoming, and
SNR in Idaho and Nevada (NatureServe 2009,
Al-Shehbaz in prep., B. Heidel pers. comm.).
Detailed status evaluations of slender mouse-
ear-cress within these jurisdictions are lacking.
Nationally, in the United States it is ranked as
N3 and globally as G4 (NatureServe 2009).

RECENT MANAGEMENT IN ALBERTA

No specific management activities for the
protection of slender mouse-ear-cress have been
undertaken in Alberta. Because slender mouse-
ear-cress is listed as Threatened in Schedule 1
of the federal Species at Risk Act , provincial
managers require that development proposals
involving potential habitat on provincial land
include rare plant surveys. If slender mouse-

ear-cress is found, steps must be taken to avoid
adverse affects on the local subpopulation.

Provincial representatives have cooperated
with representatives of Environment Canada,
Agriculture and Agri-Food Canada and the
Government of Saskatchewan in preparing a
national recovery strategy for slender-mouse-
ear-cress through the National Recovery Team
for Plants at Risk in the Prairie Provinces
(Environment Canada 2009). Consultation is
occurring with Department ofNational Defence,
industry stakeholders, First Nations, and
environmental non-government organizations.
The strategy has yet to be officially approved
and implemented.

Slender mouse-ear-cress occurs along the
proposed route of the TransCanada Keystone
Pipeline project. The National Energy Board
(NEB) approved the project in September
2007. An environmental screening report
completed by the NEB requires specific
mitigation be developed, in consultation with
Alberta Sustainable Resource Development and
Environment Canada, to minimize effects on
rare plants, and that mitigation be incorporated
into the Environmental Protection Plan and the
Operations Vegetation Management Plan for
the project (National Energy Board 2007).

There is one occurrence of slender mouse-
ear-cress recorded in the CFB Suffield
National Wildlife Area, an area managed by
the Department of National Defence with
advice from the Canadian Wildlife Service of
Environment Canada. A proposed shallow
gas infill development project in the National
Wildlife Area was recently the subject of a
panel review of the Canadian Environmental
Assessment Agency and the Energy Resources
Conservation Board. The report of the Joint
Review Panel (2009) includes recommendations
for finalizing critical habitat of slender mouse-
ear-cress, using mapped critical habitat as
exclusion areas if the project proceeds (unless
otherwise permitted under the Species at Risk

Act), and ensuring a monitoring program is
implemented to evaluate the effects of the
project.

SYNTHESIS

Slender mouse-ear-cress ( Halimolobos

virgata (Nutt.) O.E. Schulz) is an annual,
biennial or short-lived perennial herbaceous
plant that recently has undergone taxonomic
revision to Trans beringia bursifolia subsp.
virgata. In Alberta, slender mouse-ear-cress
is found within the lower South Saskatchewan
River and Red Deer River basins in the Dry
Mixedgrass Natural Subregion. Its habitat
is native grassland on silty to sandy parent
material of glaciofluvial, fluvial or eolian origin
on undulating to rolling sandy plain and river
valley slopes and terraces. Slender mouse-ear-
cress appears to be associated with ephemerally
wet depressions and drainages.

Fourteen subpopulations are recognized: one
is ranked as extirpated, one as historical, three
as failed-to-find, and nine as extant. Extant
occurrences are concentrated in the Bindloss
Plain Ecodistrict. The historical extent of
occurrence of all subpopulations is about
9998 km2; that of only extant ones is about
530 km2. Area of occupancy estimated from
element occurrence data is less than 0.05 km2;
calculated by summing occupied 1-km x 1-km
squares results in an area of occupancy of 18
km2. Substantial rare plant search effort over
the last few decades, and particularly within the
last few years, has resulted in reports of only a
few localized subpopulations of slender mouse-
ear-cress within apparently suitable habitat.

Estimates of reproducing individuals of slender
mouse-ear cress at the 14 known occurrences
range from 1 to 919 plants, and data over
multiple years at some sites suggest large
fluctuations, depending on environmental
conditions such as timing and amount of rainfall
in spring. The provincial population of slender
mouse-ear-cress is estimated to be in the order

of several thousand (3000-7000) reproductive
individuals in years when conditions are
suitable for germination and growth.

Loss of native grasslands within the range of
slender mouse-ear-cress continues to affect
habitat quality and availability. Native prairie
decline is caused primarily by agriculture
expansion, urban development, oil and
gas development and the construction of
transportation and utility corridors, as well
as the spread of invasive non-native species
in fragmented landscapes. Since 1970, bare
ground resulting from agriculture (cultivation)
and industrial development has increased 40%
and linear disturbance has increased 93% in a
study area that encompasses all of the range of
extant slender mouse-ear-cress subpopulations.
Other potential limiting factors are climate
change and altered fire and grazing regimes
beyond the range of natural variation.

To accurately define population size, extent
and trends, known locations will need to be
surveyed over a period of several years using
a well-defined monitoring protocol designed to
meet a specified degree of statistical confidence
with respect to population size and extent. As
well, a systematic approach to searching for

additional subpopulations will be required
similar to that used by Bradley (2008).

Alberta’s extant population of slender mouse-
ear-cress is approximately 45 km from the
closest known subpopulation in Saskatchewan
and 200 km from the nearest population in
Montana. No genetic exchange is expected.
Future survey is needed to determine if there
is a subpopulation in Saskatchewan contiguous
with the McNeill subpopulation in Alberta. In
addition, more taxonomic investigation of the
prairie population of slender mouse-ear-cress
is suggested to ascertain the degree to which
there are features distinct from populations of
slender mouse-ear-cress several hundreds of
kilometres to the north and to the southwest
(Environment Canada 2009).

Slender mouse-ear-cress was designated as
Endangered by COSEWIC in 1992 and re-
assessed as Threatened in 2000. It is listed on
Schedule 1 of the federal Species at Risk Act.
In Saskatchewan, slender mouse-ear-cress
is listed as Threatened under the province’s
Wildlife Act. A draft recovery strategy for
slender mouse-ear-cress in Canada has recently
been developed.

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36 pp. plus appendices.

Appendix 1: Definitions of status ranks and legal designations.

A. The General Status of Alberta Wild Species 2005 (after Alberta Sustainable Resource Development 2007)

2005 Rank

1996 Rank

Definitions

At Risk

Red

Any species known to be At Risk after formal detailed status
assessment and designation as Endangered or Threatened in
Alberta.

May Be At Risk

Blue

Any species that may be at risk of extinction or extirpation, and is
therefore a candidate for detailed risk assessment.

Sensitive

Yellow

Any species that is not at risk of extinction or extirpation but may
require special attention or protection to prevent it from becoming at
risk.

Secure

Green

Any species that is not At Risk, May Be At Risk or Sensitive.

Undetermined

Status

Undetermined

Any species for which insufficient information, knowledge or data
is available to reliably evaluate its general status.

Not Assessed

n/a

Any species that has not been examined during this exercise.

Exotic/Alien

n/a

Any species that has been introduced as a result of human activities.

Extirpated/Extinct

n/a

Any species no longer thought to be present in Alberta (Extirpated)
or no longer believed to be present anywhere in the world (Extinct).

Accidental/V agrant

n/a

Any species occurring infrequently and unpredictably in Alberta,
i.e., outside its usual range.

B. Alberta Species at Risk Formal Status Designations

Species designated as Endangered under Alberta’s Wildlife Act include those listed as Endangered or
Threatened in the Wildlife Regulation (in bold).

Endangered

A species facing imminent extirpation or extinction.

Threatened

A species likely to become endangered if limiting factors are not reversed.

Species of
Special Concern

A species of special concern because of characteristics that make it particularly sensitive to
human activities or natural events.

Data Deficient

A species for which there is insufficient scientific information to support status designation.

C. Committee on the Status of Endangered Wildlife in Canada (after COSEWIC 2009)

Extinct

A species that no longer exists.

Extirpated

A species that no longer exists in the wild in Canada, but occurs elsewhere.

Endangered

A species facing imminent extirpation or extinction.

Threatened

A species that is likely to become endangered if nothing is done to reverse the factors
leading to its extirpation or extinction.

Special Concern

A species that may become threatened or endangered because of a combination of
biological characteristics and identified threats.

Not at Risk

A species that has been evaluated and found to be not at risk of extinction given the
current circumstances.

Data Deficient

A category that applies when the available information is insufficient to (a) resolve a
wildlife species' eligibility for assessment, or (b) permit an assessment of the wildlife
species' risk of extinction.

D. Heritage Status Ranks: Global (G), National (N), Sub-national (S) (after Alberta Natural Heritage
Information Centre 2007, NatureServe 2009)

G1/N1/S1

5 or fewer occurrences or only a few remaining individuals. May be especially vulnerable
to extirpation because of some factor of its biology.

G2/N2/S2

6 to 20 or fewer occurrences or with many individuals in fewer locations. May be especially
vulnerable to extirpation because of some factor of its biology.

G3/N3/S3

21 to 100 occurrences; may be rare and local throughout its range, or in a restricted range
(may be abundant in some locations). May be susceptible to extirpation because of large-
scale disturbances.

G4/N4/S4

Typically > 100 occurrences. Apparently secure.

G5/N5/S5

Typically > 100 occurrences. Demonstrably secure.

GX/NX/SX

Believed to be extinct or extirpated; historical records only.

GH/NH/SH

Historically known; may be relocated in the future.

G7/N7/S?

Not yet ranked, or rank tentatively assigned.

E. United States Endangered Species Act (after National Research Council 1995)

Endangered

Any species that is in danger of extinction throughout all or a significant portion of its range.

Threatened

Any species that is likely to become an endangered species within the foreseeable future
throughout all or a significant portion of its range.

List of Titles in This Series

(as of August 2009)

No. 1 Status of the Piping Plover ( Charadrius melodus ) in Alberta, by David R. C. Prescott. 19 pp. (1997)

No. 2 Status of the Wolverine ( Gulo gulo) in Alberta, by Stephen Petersen. 17 pp. (1997)

No. 3 Status of the Northern Long-eared Bat ( Myotis septentrionalis) in Alberta, by M. Carolina Caceres and M.

J. Pybus. 19 pp. (1997)

No. 3 Update 2009. Status of the Northern Myotis ( Myotis septentrionalis ) in Alberta. Alberta Sustainable
Resource Development and Alberta Conservation Association. 34 pp. (2009)

No. 4 Status of the Ord’s Kangaroo Rat (Dipodomys ordii ) in Alberta, by David L. Gummer. 16 pp. (1997)

No. 5 Status of the Eastern Short-homed Lizard ( Phrynosoma douglassii brevirostre ) in Alberta, by Janice D.

James, Anthony P. Russell and G. Lawrence Powell. 20 pp. (1997)

No. 5 Update 2004. Status of the Short-homed Lizard {Phrynosoma hernandesi) in Alberta. Alberta Sustainable
Resource Development. 27 pp. (2004)

No. 6 Status of the Prairie Rattlesnake {Crotalus viridis viridis) in Alberta, by Sheri M. Watson and Anthony P.
Russell. 26 pp. (1997)

No. 7 Status of the Swift Fox {Vulpes velox) in Alberta, by Susan E. Cotterill. 17 pp. (1997)

No. 8 Status of the Peregrine Falcon ( Falco peregrinus anatum) in Alberta, by Petra Rowell and David P.

Stepnisky. 23 pp. (1997)

No. 9 Status of the Northern Leopard Frog ( Rana pipiens) in Alberta, by Greg Wagner. 46 pp. (1997)

No. 9 Update 2003. Status of the Northern Leopard Frog {Rana pipiens) in Alberta. Alberta Sustainable Resource
Development. 61 pp. (2003)

Status of the Sprague’s Pipit {Anthus spragueii ) in Alberta, by David R. C. Prescott. 14 pp. (1997)

Status of the Burrowing Owl {Speotyto cunicularia hypugaea) in Alberta, by Troy I. Wellicome. 21 pp.
(1997)

Update 2005. Status of the Burrowing Owl {Athene cunicularia ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 28 pp. (2005)

Status of the Canadian Toad {Bufo hemiophrys ) in Alberta, by Ian M. Hamilton, Joann L. Skilnick, Howard
Troughton, Anthony P. Russell, and G. Lawrence Powell. 30 pp. (1998)

Status of the Sage Grouse {Centrocercus urophasianus urophasianus) in Alberta, by Cameron L. Aldridge.
23 pp. (1998)

Status of the Great Plains Toad {Bufo cognatus) in Alberta, by Janice D. James. 26 pp. (1998)

Status of the Plains Hognose Snake {Heterodon nasicus nasicus) in Alberta, by Jonathan Wright and
Andrew Didiuk. 26 pp. (1998)

Status of the Long-billed Curlew {Numenius americanus) in Alberta, by Dorothy P. Hill. 20 pp. (1998)

No. 10
No. 11

No. 11

No. 12

No. 13

No. 14
No. 15

No. 16

No. 17 Status of the Columbia Spotted Frog (Rana luteiventris ) in Alberta, by Janice D. James. 21 pp. (1998)

No. 18 Status of the Ferruginous Hawk ( Buteo regalis ) in Alberta, by Josef K. Schmutz. 18 pp. (1999)

No. 18 Update 2006. Status of the Ferruginous Hawk (Buteo regalis ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 22 pp. (2006)

No. 19 Status of the Red-tailed Chipmunk (Tamias ruficaudus) in Alberta, by Ron Bennett. 15 pp. (1999)

No. 20 Status of the Northern Pygmy Owl ( Glaucidium gnoma californicum) in Alberta, by Kevin C. Hannah. 20
pp. (1999)

No. 21 Status of the Western Blue Flag (Iris missouriensis ) in Alberta, by Joyce Gould. 22 pp. (1999)

No. 21 Update 2005. Status of the Western Blue Flag (Iris missouriensis ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 29 pp. (2005)

No. 22 Status of the Long-toed Salamander (Ambystoma macrodactylum ) in Alberta, by Karen L. Graham and G.
Lawrence Powell. 19 pp. (1999)

No. 23 Status of the Black-throated Green Warbler (Dendroica virens) in Alberta, by Michael R. Norton. 24 pp.
(1999)

No. 24 Status of the Loggerhead Shrike (Lanius ludovicianus ) in Alberta, by David R. C. Prescott and Ronald R.
Bjorge. 28 pp. (1999)

No. 25 Status of the Plains Spadefoot (Spea bombifrons) in Alberta, by Richard D. Lauzon. 17 pp. (1999)

No. 26 Status of the Trumpeter Swan (Cygnus buccinator ) in Alberta, by M. Lynne James. 21 pp. (2000)

No. 27 Status of the Pygmy Whitefish (Prosopium coulteri ) in Alberta, by William C. Mackay. 16 pp. (2000)

No. 28 Status of the Short-eared Owl (Asio flammeus) in Alberta, by Kort M. Clayton. 15 pp. (2000)

No. 29 Status of the Willow Flycatcher (Empidonax trailin') in Alberta, by Bryan Kulba and W. Bruce
McGillivray. 15 pp. (2001)

No. 30 Status of the Woodland Caribou (Rangifer tarandus caribou ) in Alberta, by Elston Dzus. 47 pp. (2001)

No. 3 1 Status of the Western Spiderwort (Tradescantia occidentalis ) in Alberta, by Bonnie Smith. 12 pp. (2001)

No. 32 Status of the Bay-breasted Warbler (Dendroica castanea) in Alberta, by Michael Norton. 21 pp. (2001)

No. 33 Status of the Cape May Warbler (Dendroica tigrina) in Alberta, by Michael Norton. 20 pp. (2001)

No. 34 Status of the Whooping Crane (Grus americana ) in Alberta, by Jennifer L. White. 21 pp. (2001)

No. 35 Status of Soapweed (Yucca glauca) in Alberta, by Donna Hurlburt. 18 pp. (2001)

No. 36 Status of the Harlequin Duck (Histrionicus histrionicus) in Alberta, by Beth MacCallum. 38 pp. (2001)

No. 37 Status of the Grizzly Bear (Ursus arctos ) in Alberta, by John L. Kansas. 43 pp. (2002)

No. 38 Status of the Wood Bison (Bison bison athabascae) in Alberta, by Jonathan A. Mitchell and C. Cormack
Gates. 32 pp. (2002)

No. 39 Status of the Bull Trout ( Salvelinus confluentus ) in Alberta, by John R. Post and Fiona D. Johnston. 40 pp.
(2002)

No. 40 Status of the Banff Springs Snail {Physella johnsoni ) in Alberta, by Dwayne A. W. Lepitzki. 29 pp. (2002)
No. 41 Status of the Shortjaw Cisco ( Coregonus zenithicus) in Alberta, by Mark Steinhilber. 23 pp. (2002)

No. 42 Status of the Prairie Falcon ( Falco mexicanus ) in Alberta, by Dale Paton. 28 pp. (2002)

No. 43 Status of the American Badger ( Taxidea taxus ) in Alberta, by Dave Scobie. 17 pp. (2002)

No. 44 Status of the Yucca Moth (Tegeticula yuccasella) in Alberta. Alberta Sustainable Resource Development.

21 pp. (2002)

No. 45 Status of the White-winged Scoter ( Melanitta fusca deglandi ) in Alberta. Alberta Sustainable Resource
Development. 15 pp. (2002)

No. 46 Status of the Lake Sturgeon ( Acipenser fulvescens) in Alberta. Alberta Sustainable Resource
Development. 30 pp. (2002)

No. 47 Status of the Western Silvery Minnow ( Hybognathus argyritis) in Alberta. Alberta Sustainable Resource
Development. 24 pp. (2003)

No. 48 Status of the Small-flowered Sand Verbena ( Tripterocalyx micranthus) in Alberta. Alberta Sustainable
Resource Development. 24 pp. (2003)

No. 49 Status of the Brown Creeper ( Certhia americana) in Alberta. Alberta Sustainable Resource Development.
30 pp. (2003)

No. 50 Status of the Mountain Plover ( Charadrius montanus ) in Alberta. Alberta Sustainable Resource
Development. 25 pp. (2003)

No. 5 1 Status of the St. Mary Shorthead Sculpin (provisionally Cottus bairdi punctulatus) in Alberta. Alberta
Sustainable Resource Development. 24 pp. (2003)

No. 52 Status of the Stonecat (Noturus flavus ) in Alberta. Alberta Sustainable Resource Development. 22 pp.
(2003)

No. 53 Status of the Sage Thrasher ( Oreoscoptes montanus) in Alberta. Alberta Sustainable Resource
Development. 23 pp. (2004)

No. 54 Status of the Tiny Cryptanthe ( Cryptantha minima) in Alberta. Alberta Sustainable Resource
Development. 39 pp. (2004)

No. 55 Status of the Slender Mouse-ear-cress ( Halimolobos virgata) in Alberta. Alberta Sustainable Resource
Development. 27 pp. (2005)

No. 55 Update 2009. Status of the Slender Mouse-ear-cress (. Halimolobos virgata or Transberingia bursifolia
subsp. virgata) in Alberta. Alberta Sustainable Resource Development and Alberta Conservation
Association. 28 pp. (2009)

No. 56 Status of the Barred Owl ( Strix varia) in Alberta. Alberta Sustainable Resource Development. 15 pp.
(2005)

No. 57 Status of the Arctic Grayling ( Thymallus arcticus) in Alberta. Alberta Sustainable Resource Development.
41 pp. (2005)

No. 58 Status of the Weidemeyer’s Admiral ( Limenitis weidemeyerii ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 1 3 pp. (2005)

No. 59 Status of the Porsild’s Bryum ( Bryum porsildii) in Alberta. Alberta Sustainable Resource Development
and Alberta Conservation Association. 30 pp. (2006)

No. 60 Status of the Western Grebe ( Aechmophorus occidentalis ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 29 pp. (2006)

No. 61 Status of the Westslope Cutthroat Trout ( Oncorhynchus clarkii lewisii ) in Alberta. Alberta Sustainable
Resource Development and Alberta Conservation Association. 34 pp. (2006)

No. 62 Status of the Limber Pine ( Pinus flexilis ) in Alberta. Alberta Sustainable Resource Development and
Alberta Conservation Association. 17 pp. (2007)

No. 63 Status of the Whitebark Pine {Pinus albicaulis ) in Alberta. Alberta Sustainable Resource Development
and Alberta Conservation Association. 22 pp. (2007)

No. 64 Status of the Western Small-footed Bat {Myotis ciliolabrum ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 24 pp. (2008)

No. 65 Status of the Verna’s Flower Moth ( Schinia vema) in Alberta. Alberta Sustainable Resource Development
and Alberta Conservation Association. 1 7 pp. (2008)

No. 66 Status of the Athabasca Rainbow Trout {Oncorhynchus mykiss ) in Alberta. Alberta Sustainable Resource
Development and Alberta Conservation Association. 32 pp. (2009)

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