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Full text of "Further study of the garter snake, Thamnophis sirtalis, in northeastern Kansas"

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Herp. 



LIBRARY 



QL 
666 

F4"\'/^V/^'M'f"V/'V/^ l-J/J^I/l/y^C^ AUG 6 2001 



2001 



cientific Papers 



uKllS?, 



Natural History Museum 
The University of Kansas 



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15 June 2001 Number 19:1-6 

Further Study of the Garter Snake, Thamnophis sirtalis, 

in Northeastern Kansas 

By 

^ Henry S. Fitch 



§■1 



js: a 



t— rt 



tu c 



FzYc/i Natural History Resen>ation, The University ofKa^as 
2060 East 1600 Road, Lawrence, Kansas 66044-9450, USA 



CONTENTS 

o ^ ; ABSTRACT 1 

; INTRODUCTION '2 

; Acknowledgments 2 

MATERIALS AND METHODS 2 

; RESULTS 2 

^'^ DISCUSSION 5 

A 1 . LITERATURE CITED 6 

ts ^ ^ 

S S - ABSTRACT The red-sided garter snake, Thamnophis sirtalis parietalis, is a prominent member of the 

local snake fauna at the Fitch Natural History Reservation and has been a subject of field study over 
the past 53 years. Although several publications in whole or in part, have been devoted to this species, 
some aspects of its ecology have remained poorly known; some of these are dealt with in the present 
paper. Herein, I discuss the range of variation in color and pattern, and compare the frequencies of 
pattern types in males and females; I also compare the sexes with each other and with immatures in 
their ecological traits including vagility and their fidelity to specific locations. Comparison of feeding 
records show major differences in food habits between the sexes and between young and adults. A 
northern population of this same subspecies in the Interlake Region in Manitoba, Canada, is com- 
pared behaviorally with the Kansas population on the basis of recent studies. 

Key words; Dorsolateral area; Funnel trap; Intersquamal color; Probability of capture; Thamnophis sirtalis 
parietalis. 

© Natural History Museum, The University of Kansas ISSN No. 1094-0782 



Scientific Papers, Natural History Museum, The University of Kansas 



INTRODUCTION 



The common garter snake, Thamnophis sirtalis, is eco- 
logically important and geographically widespread; it oc- 
curs throughout most of the United States (except the arid 
southwestern one-fourth) and in the southern half of 
Canada (Ruthven, 1908). A large amount of literature ex- 
ists regarding its local occurrence, identification, and in- 
teractions with other species (Fitch, 1980). It is in fact one 
of the best known of North American snakes. The recent 
book by Rossman et al. (1996) summarizes much informa- 
tion concerning the species. My acquaintance with the spe- 
cies began with studies of the west coast garter snakes at 
the University of California's Museum of Vertebrate Zool- 
ogy in the 1930s. (Fitch, 1941). With my becoming the first 
superintendent of the University of Kansas Natural His- 
tory Reservation in 1948, 1 had opportunity to study a lo- 
cal population of the red-sided garter snake {ThamnopJiis 
sirtalis parietalis) and subsequently published an ecologi- 
cal study on that snake (Fitch, 1965). In that study the popu- 
lation on the Reservation was compared with that in 
Harvey County State Park, 140 miles to the southwest; geo- 
graphic variation over the entire range was discussed, and 
the two local populations were compared with respect to 
habitat, temperature relationships, food habits, breeding. 



growth, movements, defense and escape, natural enemies, 
parasites, composition of the population and numbers. In 
my synthesis of a Kansas snake community (Fitch, 1999), 1 
presented data on the common garter snake dealing with 
traits of the species, behavior, size relationships, pattern 
types, tail functions, spatial relationships, kinds of prey, 
reproduction, growth, numbers, and geographic differen- 
tiation. Since that study was completed, three more sea- 
sons of field work on garter snakes have been finished. 
The present report deals with aspects of the ecology not 
undertaken or adequately treated in previous publications, 
to describe in detail the color pattern phases and their in- 
cidence in a large sample, and to compare the sexes with 
each other and with immatures in their ecological traits. 

ACKBOWLEDGMENTS 

I thank William E. Duellman for his advice regarding 
the content and organization of this paper. I am indebted 
to Neil B. Ford and Stevan J. Arnold for their many help- 
ful suggestions. My daughter, Alice F. Echelle, helped me 
with various phases of the early field work and also made 
suggestions for improving the original manuscript. Also, 
I thank the many students who have helped me capture 
snakes over the past 53 years. 



MATERIALS AND METHODS 



Garter snakes were captured in wire funnel traps, or 
by hand from beneath shelters, both metal and wooden, 
and these contrasting techniques were used on different 
areas. Data routinely recorded from each snake captured 
included sex, snout-vent length, tail length, color and 
markings, and stomach contents. Color pattern was de- 
scribed with special attention to the vertebral stripe, the 
dark dorsolateral area, and the series of pale intersquamal 
marks on the body. Lincoln Index censuses were made from 
time to time on relatively small and discrete areas of in- 
tensive study. Each census was based on two consecutive 
sampling periods; the ratio of marked snakes (from the 
first sampling) to unmarked snakes in the second sampling 
was the basis for an estimate; it was obvious that the 
snakes' movements prevented a highly accurate census, 
and the longer the sampling period the more distorted the 
census figure, because previously marked snakes wan- 



dered away and were replaced by new ones. Food habits 
were studied by palping food items from the stomach up 
into the mouth for identification, and comparisons in- 
volved male and female snakes, adults versus first-year 
young, areas of different habitats and changes over time. 
Areas of most Intensive study on Fitch Natural His- 
tory Reservation (FNHR) included House Field (10 ha in 
the headquarters area sampled from shelters in the 1990s), 
and Quarry Field (a 3.36 ha hilltop field on the northern 
edge of the reservation). On the adjacent Nelson Environ- 
mental Study Area (NESA), study areas included the Elec- 
tric Mouse Pens (in the northwestern sector, 9.65 ha 
sampled with traps in the 1990s), the Fish Pond Pens (2.6 
ha south of NESA headquarters, sampled with traps in the 
1990s), and Plots 4 and 5 in the southeastern part of the 
Biotic Succession Area (5.0 ha , sampled with shelters, 1986- 
2001). 



RESULTS 



Color pattern. — Thamnophis sirtalis has a longitudi- 
nally striped pattern, and is one of the most brightly col- 
ored snakes. There is much variation, both geographic and 
individual, in color and pattern, but ontogenetically there 
is little change, which involves a brightening from the 
rather dull color of the neonate. Between the scales on loose 
skin of the dorsolateral area are the colored marks that give 
the subspecies its vernacular name "red-sided." These 



marks are not always red and are highly variable in size 
and color, providing a variety of pattern types. Table 1 
shows the relative frequency of nine pattern types in the 
local population and shows differences between the sexes. 
Actually, individual variation is such that a continuum 
might be established among all nine types. The 
intersquamal marks are arranged in transverse alternat- 
ing series, with the two lower rows and the three upper 



Further Study of the Garter Snake 



Table 1. Pattern variation in intersquamous marks of dorsolateral area 
in a local population of Thamnophis sirtalis parietalis. Numbers are per- 
centages of total sample size for each sex (669 males, 1029 females). 





Intersquamous pattern 


Males 


Females 


Allied 


26.5 


34.5 


All yellow 


5.5 


3.5 


All green 


3.9 


2.7 


All blue 


3.2 


1.2 


Uppermost row pale (russet, 






ivory, green, or blue) 


19.0 


14.9 


Two upper rows pale 


26.5 


26.6 


Three upper rows pale 


12.7 


9.1 


Four upper rows pale 


2.5 


2.3 


Two upper rows missing 






(T.s./iWn' pattern) 


0.1 


0.2 





offset and alternating, separated by about the length of 
one scale from the next in front or behind. The lowest row 
is just above the lateral stripe and its marks are the largest; 
those marks farther from the lateral stripe become progres- 
sively smaller and less colorful. The two lower marks are 
on each side of the fourth scale row; the three upper marks 
involve scales of the fifth, sixth, and seventh rows. These 
marks on the dorsolateral area are sometimes all one color 
(in both sexes combined, 26.3% red, 3.6% yellow, 2.5% 
green, 2.2% blue), but in some cases only the lower rows 
are red, and the upper (four, three, two or one) are paler, 
faintly yellow, green or blue. In occasional individuals, 
the upper series (two or three nearest the dorsal stripe) 
are missing, and these snakes have essentially the pat- 
tern of the West Coast subspecies, Thamnophis sirtalis 
fitchi. In the majority of local snakes, the upper marks 
are not red but are pale, ivory, or delicately tinted with 
yellow, green, or blue. In a small minority, there is no 
red in the pattern and all dorsolateral marks are of pale 
color. 



The yellow vertebral stripe is perhaps the most char- 
acteristic trait of the species, but in the local population it 
also is subject to much individual variation. Typically the 
stripe is bright yellow and involves the vertebral scale row 
and half of the adjacent row on each side, but it may be a 
dull, muddy yellow, may be broader than the typical one 
and two halves of scale rows, and may have indistinct 
edges. The dorsolateral area between the vertebral stripe 
and the lateral stripe on each side is typically sepia-colored 
or almost black, but may be paler brown or gray, with two 
alternating rows of darker spots and five pairs of transverse 
markings, largely confined to the skin between the scales. 

Movements and abundance-Behavioral differences 
between the sexes affect their relative probability of cap- 
ture (Table 2). For example, site fidelity is more prominent 
in females. This is illustrated by attempts to apply a Lin- 
coln Index census to the data. In 1998 in House Field, snakes 
were captured exclusively by hand. There were 43 males 
and 55 females (excluding the young born in late summer). 
Of the 98 snakes in the sample, 57 were caught in the first 
half of the season (March, April, May. June), 41 were caught 
in the latter part (July through October) and 10 of these 
were captured in both early and late periods. From the 
ratio of recaptures in late summer and fall the Lincoln In- 
dex indicates a population of approximately 234. But if 
the census is applied separately to males and females, the 
figures for females are 38 for the first half of the season, 17 
for the second half, and 8 for both, with the equation indi- 
cating a population of 80.8 individuals. For males, the cor- 
responding figures are 19, 24 and 2, suggesting a popula- 
tion of 228 individuals. Intuitively, it seems that the figure 
for males is much too high, and is the result of only two 
recaptures, because most of those present in spring and 
early summer had moved away by the time of the late sum- 
mer-fall sampling. Censusing from the ratio of marked to 
unmarked snakes assumes there is no movement to or from 



Table 2. Relative probability of capture of the red-sided garter snake. 







Method of 
capture 


Sex 


Total 






Number of 


captures 










Twice 


Three times 

N % 


Four t 

N 


imes or more 


Area 


N 


% 


% 


House Field 


Under shelters 


cf 


175 


76 


43.4 


16 


9.1 


6 


3.4 




or by hand 


9 


184 


103 


56.0 


75 


38.7 


27 


14.7 


Biotic Succession Area 


Under shelters 


cf 


46 


5 


10.9 


1 


6.5 


_ 


_ 




or by hand 


9 


93 


24 


25.8 


11 


11.8 


3 


3.2 


Nelson Environmental 


Wire funnel 


cf 


140 


35 


25.0 


15 


10.7 


4 


2.9 


Study Area 


traps 


9 


140 


50 


35.7 


20 


14.3 


12 


8.6 


Quarry 


Wire funnel 


cS 


35 


10 


28.6 


8 


22.9 


- 


- 




traps 


9 


51 


30 


58.8 


17 


33.3 


6 


16.8 


Hilltop outcrop 


Wire funnel 


cf 


53 


3 


6.0 


- 


- 


- 


- 




traps 


9 


81 


5 


6.3 


1 


1.3 


- 


- 


Reservation, 


Wire funnel 


cf 


457 


48 


10.5 


10 


2.2 


10 


2.2 


1950s & 1960s 


traps 


9 


635 


94 


14.8 


23 


3.6 


19 


3.0 





Scientific Papers, Natural History Museum, The University of Kansas 



398 


106 


.16.3 


80.6 


3.67 


2.23 


44 


13 



Table 3. Distances between capti.ire points and implied areas of activity 
for male, female, and young red-sided garter snakes. 

Males Females Young 



N U7 

Mean distances (m) between capture points 117.9 

Implied area (ha) 3.77 

Recaptures reflecting no net movement 9 



a study area. However, there is always some movement, 
depending on the length of time involved. In male garter 
snakes movement is especially prominent, and it is essen- 
tial to have short sampling periods in order to minimize 
the effect (Fitch, 1999) and to be aware of the error caused 
by movement. Compared with females, adult males move 
farther and more frequently, and they have less tendency 
to return to any specific location. Therefore, they are less 
susceptible to recapture, and this affects the ratios in Lin- 
coln Index censuses. 

Table 3 shows differences between the sexes and be- 
tween adults and yoi-mg in distances moved. The young 
were all first-year individuals, but most had made sub- 
stantial growth before their first capture. They were mostly 
in the range of 300-400 mm in snout-vent length, and thus 
had about doubled in length since birth. In these partly 
grown young, the average movements were substantially 
less than in adults of either sex. It is believed that even 
smaller young, down to the size of neonates would show 
progressively shorter movements and their home ranges 
would be progressively smaller. Adults of both sexes are 
similar in their movements compared with young, which 
move within smaller areas. Adult females and young are 
alike (but differ from males) in their tendency to return 
frequently to favored spots. 



On the FNHR until the 1980s, and at the pens area 
in the NESA, samples of snakes were obtained with wire 
funnel traps and consisted almost entirely of adults, 
because immatures easily pass through the quarter-inch 
wire mesh of the funnel traps. In the Biotic Succession 
Area (BSA) of the NESA and FNHR in the late 1980s 
and 1990s, sampling was accomplished by distributing 
wooden and metal shelters, which presumably were 
used by snakes of all sizes and ages indiscriminately, 
but young were relatively few in the upland habitat of 
the BSA. 

Food habits. — Studies of food habits have shown 
major geographic differences within the species but usu- 
ally have not compared food of the sexes, or compared 
adults and young. In the local population such differ- 
ences exist and are shown in Tables 4 and 5. Table 4 
shows the total food sample divided into 48 categories 
to bring out differences between the sexes, between 
adults and young, and between areas of different habi- 
tat. 

There are striking differences between areas. The 
many young captured in House Field had eaten earth- 
worms almost exclusively. One had eaten a small slug 
{Deroceras laeve) and several had eaten newly metamor- 
phosed hylids {Acris and Psendacris). Another impor- 
tant difference was predation on small mammals by 
adult females (30 records, 16 of them on Microtus 
oclirogaster) compared with only one record for a male 
snake, which had eaten an individual of the much less 
bulky Reithwdontomys megalotis. 

Frogs {Rana blairi and R. catesbeiana) made up a major 
part of the food and were well represented in each local- 
ized sample. Raim blairi was eaten about twice as often as 
R. catesbeiana, and none of the latter species was much more 



Table 4. Prey of the red-sided garter snake in four areas of the Fitch Natural History Reservation (FNHR) and Nelson Environmental Study Area 
(NESA) comparing sexes, mean snout-vent lengths in mm (SVL ± 1 SE), and numbers (N) of snake predators. BSA = Biotic Succession Area of NESA. 









House Field 




FNHR 




BSA 




NESA Pens 




Sex 




1980-2000 




1950-1990 




1986-2000 




1986-2000 


Prey 


N 


SVL 


N 


SVL 


N 


SVL 


N 


SVL 


Earthworm 


Cf 


54 


397.9 ± 12.1 


9 


517.7 


2 


356 


_ 


_ 




9 


81 


430.6 ±11.3 


4 


475.8 ±21.1 


6 


480.8 ±16.9 


1 


517 


Microtus 


a 


_ 


_ 


_ 


— 


_ 


- 


- 


_ 




9 


1 


623 


3 


675 


6 


649.3 ± 32.7 


6 


705.7 ±21.5 


Other mammals* 


<s 


_ 


- 


1 


490 


- 


- 


_ 


- 




9 


4 


600.8 ± 28.8 


10 


636.4 ± 3.14 


1 


783 


4 


612.3 ± 8.8 


Rana* 


cf 


12 


496.3 ±1.5 


15 


488.9 ± 2.5 


1 


540 


6 


536.7 ±6.2 




9 


23 


567.6 ± 4.3 


21 


549.0 ± 6.7 


4 


669.3 ± 14.4 


27 


623.0 ± 13.8 


Bufo* 


CJ 


3 


438.6 


6 


403..3 ± 0.65 


_ 


- 


2 


374.0 




9 


3 


582.4 


7 


615.3 ±6.2 


4 


673.0 ± 18.5 


1 


745 


Other amphibians* 


cf 


3 


354.5 


4 


364,8 ± 14.1 


4 


442.5 + 74.2 


3 


338.3 




9 


9 


442.2 


7 


562.4 ± 10.0 


5 


532.6 ± 12.1 


9 


591.4 ±3.9 





* "Other mammals" includes Peromyscus, Reithrodontomys, Blarina, and Cryptotis. "Rana" includes R. blairi and R. catesbeiana. "Bufo" includes B. 
americanus and B. ivoodhousii. "Other amphibians" includes Acris, Hyla, Pseudacris, and Gastrophiyne. 



Further Study of the Garter Snake 



Table 5. Prey eaten by red-sided garter snakes on the FNHR and adjoin- 
ing areas and sizes of snake predators. In columns of SVL, the first line 
is the obseri'ed range and the second line is the mean ± 1 SE. Measure- 
ments in mm. 









SVL of male 




SVL of female 


Kind of prey* 


N 


predator 


N 


predator 


AUohbophora caliginosa 
(earthworm) 


60 


225-666 
392.5 ± 11.7 


88 


226-666 
432.1 ± 10.5 


Rana blairi 


47 


411-610 
522.3 ±9.5 


54 


363-780 
602,9 ± 13.3 


Rana catesbeiana 


7 


419-582 
487.4 ±23.4 


13 


531-834 
637.8 ±32.7 


Rana sp. 


1 


497 


8 


294-630 
554.9 ± 46.8 


Bufo amerkaniis 


5 


368-596 
458.0 ±52.8 


13 


519-745 
638.5 ± 52.9 


Bufo woodbousii 


5 


459-578 
432.6 ±40.1 


6 


488-673 
616.7 ±40.4 


Hyla chnjsoscelis 


5 


243-596 
426.6 ± 63.9 


9 


374-653 
571.7 ±30.5 


Acris crepitans 


7 


228-580 
413.7 ± 55.2 


10 


240-712 
480.6 ± 59.8 


Pseudacris triseriata 


2 


383-406 
394.0 


4 


303-688 
487.3 ± 96.0 


Microtus ochrogaster 


- 


: 


17 


585-810 
691.1 ±23.6 


Pewmysciis leucopus 


- 


- 


8 


510-850 
647.3 ± 44.1 


Reithrodontomi/s megalotis 


- 


- 


5 


565-783 
637.4 ± 37.9 





*Prey species with few records (sex and SVL of snake predator in paren- 
theses): Cryptotis panm (9, 615), Synaptomys cooperi (9, 648), Cardinalis 
cardinalis (9, 713), Melospiza Hncolnii (9, 520). Unidentified bird (9, 634), 
Diadophis punctatiis (9, 520), Gastrophryne olivacea ( 9, 600),Deroceras laeve 
(9, 303). 

than half grown. Toads {Bufo) were taken about half as of- 
ten as frogs {Rana), and several of those eaten, especially 
of the smaller B. americanus, were adults. Of the tree frogs 
{Hyla chiysoscelis) eaten, several had been taken by snakes 
found at the hilltop rock outcrops where the snakes hiber- 
nate. Perhaps the frogs also had come to these places in 
search of hibemacula. 

In a total of 375 prey animals, most were amphibians 
(8 kinds), small mammals (6 kinds) and earthworms, with 
an occasional bird, snake, or slug. Food of the first-year 
young consisted almost exclusively of earthworms, but 
with an occasional newly metamorphosed anuran. Of 32 
small mammals eaten, 31 including all the microtines (13) 
were taken by adult females (510 to 850 mm SVL) and only 
one mammal, a harvest mouse {Reithrodontomys) was eaten 
by an adult male (490 mm SVL). Frogs {Rana) and toads 
{Bufo) were eaten chiefly by the adult snakes, especially 
by females. It should be emphasized that mammals, al- 
though too bulky to be ingested by males and immatures, 
are regularly eaten by adult females and constitute an im- 
portant resource for the developing embryos. 



DISCUSSION 
The widespread occurrence of Thamnophis sirtalis 
parietalis is evidence of its plasticity and ability to thrive 
under diverse conditions. In recent decades, the snake dens 
of Manitoba Canada, have attracted much attention. There, 
field studies of far northern representatives of T. s. parietalis 
by Aleksiuk (1976), Aleksiuk and Stewart (1971), Crews et 
al. (1988), Gregory (1974), Joy and Crews (1988), Shine et 
al. (2001), and Shine and Mason (2001) have revealed the 
following traits: 

1. Formation of huge denning aggregations Qoy and 
Crews, 1985; Crews et al, 1984); thousands of snakes hi- 
bernate together in deep limestone sinks. 

2. Formation of massive mating aggregations at, or 
near, the hibemacula, as recently emergent males pile up, 
sometimes by the hundreds, to court emerging females 
(Gregory, 1977). 

3. Presence of "she-males" m mating aggregations 
(Shine and Mason, 2001); these are the most recently 
emerged males, weak and debilitated from their long so- 
journ underground, but possessing the ability to produce 
pheromones Hke those of emergent females that are highly 
attractive to males (Shine et al., 2001). Within a time-span 
as short as one day such males lose much of their attrac- 
hveness but gain in strength and vigor. 

4. Massive mortality at and near the dens (Shine et al., 
2001). Predators, including crows, kill many, but much 
larger numbers are victims of their own social system. The 
pUe ups that occur in mating aggregations may suffocate 
hundreds of the participants. Mortality is selective; males 
that are eliminated tend to be the smallest, thinnest, and 
weakest of those participating, and their deaths may ben- 
efit the population at large. However, the females killed 
tend to be the largest and heaviest, as these are the most 
attractive and summon the largest retinues of males. 

5) Long distance dispersal (up to 20 km) from the dens, 
as the emergent snakes scatter to exploit extensive marsh- 
lands in the region of the dens, where they feed on a vari- 
ety of marshland ariimals, notably the wood frog, Rana 
sylvatica (Gregory and Stewart, 1975). 

It must be realized that these combined traits are not 
characteristic of the subspecies T. s. parietalis but, instead, 
result from the unique selective pressures generated by 
the environment near the northern edge of the range. None 
of the behaviors described above has been observed in the 
red-sided garter snakes of northeastern Kansas, thereby 
indicating widely divergent responses to contrasting en- 
viroriments. No comparison of morphology or color pat- 
tern has yet been made between the Kansas population of 
T. s. parietalis and that of Manitoba. 

The longitudinally striped pattern is adaptive in that 
it conceals motion as the snake moves through dense veg- 
etation. It is sigruficant that adult females, larger and more 



SciENTinc Papers, Natural History Museum, The University of Kansas 



aggressive than male counterparts, are somewhat more 
likely to have red in the pattern and to respond to con- 
frontation with sematic display, whereas males are less 
aggressive and more inclined to escape and to seek con- 
cealment. 

Shine (1991) pointed out that Thamnophis are unusual 



among snakes for their marked sexual dimorphism in head 
size, with the females having relatively larger heads. Mam- 
mals, although too bulky to be ingested by males and 
immatures, are eaten regularly by adult females. This di- 
etary difference helps to explain how this sexual dimor- 
phism is maintained. 



LITERATURE CITED 



Aleksiuk, M. 1976. Reptilian hibernation. Evidence of adaptive strate- 
gies in Thamnophis sirtalis parietalis. Copeia 1976:170-178. 

Aleksiuk, M., and K. Stewart. 1971. Seasonal change in the body compo- 
sition of the garter snake (Thamnophis sirtalis parietalis) at northern 
latititudes. Ecology 52:485-490. 

Crews, D., M. Diamond, R. Tokarz, B. Camaztne, and W. Garstka. 1984. 
Hormone independence of male sexual behavior in a garter snake. 
Hormonal Behavior 18:29-41. 

Crews, D., V. Hingorani, and R. J. Nelson. 1988. Role of the pineal gland 
in the control of annual reproductive, behavioral, and physiologi- 
cal cycles in the redsided garter snake {Thamnophis sirtalis parietalis). 
Journal of Biological Rhythms 3:293-302. 

Fitch, H. S. 1941. Geographic variation in the garter snakes of the species 
Thamnophis sirtalis in the Pacific Coast Region of North America. 
American Midland Naturalist 26:570-592. 

Fitch, H. S. 1965. An ecological study of the garter snake, Thamnophis 
sirtalis. University of Kansas Museum of Natural History 15:493-564. 

Fitch, H. S. 1980. Thamnophis sirtalis. Catalog of American Amphibians 
and Reptiles 279:1-4. 

Fitch, H. S. 1999. A Kansas Snake Community: Composition and Changes 
over Fifty Years. Malabar, Florida: Krieger Publishing Company, xi 
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