Rodents and field sowing;

994-

UC-NRLF

data is not for publication
without consent of the Forest
Service. )

SS D-6

Columbia - Studies

Nursery Experiments.

RODENTS AND FIELD SOWING

By C. P. Willis
November 19, 1912.
---o---

The study was started on the T/ena tehee National
Forest after observing serious injuries to seed spots by
rodents boring into them and eating the seed sown. A se-
ries of tests was carried on on this Forest with the ain
of obtaining some substance so repulsive to white-footed
mice that seed treated v/ith it would not be molested when
sown in the field. Mice were kept in captivity for the
tests, and were fed untreated and treated seed each day.
The following is the summary of these tests:

Wenatchee Tests with Gaged Ilice (See file copy of prog-
ress report. )

The following table shows the substances test-
ed with white-footed mice, and the value of each accord-
ing to percentage of good seed left untouched.

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Number of seed left for

Substance used in Per cent different mice
treatment of seed Mouse House Mouse House

left 7 8 9 10

Zenoleum and sulphur

60

30

56 9o#

Zinc chloride

56

0

72 no

lodoform

54

76$

50$ 36$

Nux vomica

44

60

74- 5#

Nap thai en e

43

7#

42 78$

Tincture of iron

19

20

Glycerated asafoetida

14

0

30

Tannic acid

16

0

35

Carbolic acid

6

6

Powdered sulphur

2

2

Zenoleum

2

2

Tobacco solution

1

1

Copper sulphate

1

1

Lime and sulphur

0

0

Borax

0

0

"

Glycerine soap

0

0

Mercuric chloride

0

0

Belladonna

0

0

Tincture red pepper

0

o#

Quinine

0

#150 treated and 1JO untreated seed were
each day fed. All were Douglas fir seed, "but
two different lots 7/ere used. In one lot a
count of 500 seed showed 105 out of 150 had
kernels. This lot was used where the # is not
given. The othe^ lot had 97 good seed out of
150 and this was used where a # is given after
the figure.

It is thought that the test was severe and that
where 40^ or 50^ of the treated seed were eaten in the
cage that few or none would have been touched in the field.
This is merely a supposition based upon the following facts :
The mouse was in each case confined to a small space; he
was underfed; the treated seed was easier to reach than the
untreated seed in the cage.

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Wind River Tests with Gaged Mice and Chipmunks:

Tests similar to the Wenatohee ones were a few
months later carried on at the V7ind River Nursery.

Zinc chloride, which was next to the best sub-
stance -cried on the Wenatchee Forest, failed absolutely.
Two tests were made with different mice, and in each case
all the treated seed were eaten.

lodofonn, the third best substance on the Wenat-
chee, was not used in the sanig form as previously, but in
the way it was us ed it failed. Instead of putting the
iodoform on the seeds, it was placed on the surface of the
earth :ir which seed was buried. One-fourth teaspoonful
was cpvi.uTOLed over soil in a box 5" x 6" in size, but seed
buried '1-1/4" under it were smell ed and dug up.

Hap thai ene, fifth best on the Wenatchee, wae

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used ae in the case of iodofonr placed or: the surface of

soil in which seed was buried, instead of on the seed as
formerly. In the form used last it failed.

ITux vomica, iodoform, starch, and flour, made
into a pellet 3/8 tf to 1/2" in diameter, inclosing 10 seed,
was only fairly efficient. Of b pellets, two fed to each
of three mice, 3 were nibbled, .1 broken to pieces, and
the seed eaten, and 2 were left untouched.

The only conclusion which can be rnaae is that

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the Wenatchee tests were not as severe as was thought, and.
that the ideal substance is yet to be discovered.

Various other pellets, pastes, etc., were tried
and among them only one form of one mixture gave satisfac-
tory results so far as protection goes. This was a pellet
composed of equal parts of tannic acid powder, tincture
red peper, tincture of "belladonna, and enough flour to
make thick paste, the whole enclosing ten seeds and being
about 1/2" in diameter and four sided. The pellets were
used twice with one mouse, once with two other mice, and
once with two different chipmunks, and in all cases formed
perfect protect ion. The seed, co-old ha idly be sown in rush
foim, lio*rf-,T e:r, as it undoubtedly would take too long tc
germinate, BO -chis substance i^ -.iCt practical. The sf.nxe
mixture in paste foim was of 5°> 'approximately) value,
failing absolutely in one of two oa/.ee. The omj ;• G ion of
one of the poisons seemed to nullify the protect! ve value.

Alter tests in the treating of seed with repul-
sive substances had been carried to this point, it seemed
best to try other methods of prot-ccti on. Accordingly seed
was enclosed in screen wire cylinders, about Iu nigh and
1/3" in diameter, with two thicknesses of wire as protec-
tion to the seed, since it was eoon fcunrL that 'die mice
could nibble the seed wten but a single thictaiess was IB ed.

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Cage tests indicated t-iat this was sufficient protectiov

to the seed. To give further tests, a nursery bed frame

was made mouse proof, spots representing seed spots we:;.;..

sown over the ground surface enclosed, a couple of mice

were turned into the area, and the results following were

obtained:

Results of P & S No. ?:

There were seed spots in the experimental
bed. These differed from one another in the seed being
encased in cartridges of screen wire, or not so encased;
in different sizes and forms of the cartridges; in dif-
erent depths of covering; and in different number of seed
per spot, as well as firming the covering soil or leaving
it loose.

Encasing seed in screen cartridges is not effi-
cient protection, llany of the cylinders were dug up,
others were exposed by the mouse digging around them,
while seed was extracted in two instances by the mouse
gnawing the top of the cylinder and reaching the seed in
this way without digging up the cartridge. It does not
seem that the cartridges could be used even if they gave
better protection, for the stems and roots of the .cod--
lings do not extend vertically, and consequently ait more
apt to pierce the sides of the grlinder passing through

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the wire mesh, than to miss the wire by passing through
the openings of the cartridge.

The ordinary method of oeed spotting, 50 seeds
to the spot, 1/2" covering of soil, either firmed or loose,
gave as good results as any other method tried, but never-
theless suffered greatly through the mouse damage,
tfotes dm the Smelling Powers of ITice:

In the last experiment seed was sown at depths
of 1-1/2" and 2-1/2" in some of the tests. Part of the seed
in the 1-1/2" sowing was dug up, while the surface soil on
one of the 2-1/2" spots was nosed. It is obvious, therefore,
that mice can smell seed even through 2-1/2" of soil. Since
deeper sowing than 1-1/2" would make the coming up of the
plants very uncertain, it is not possible to sow seed deep
enough to prevent their detection by rodents.

In cage tests a box 5" x 6" x 1-1/2" was filled with
soil, seed sown at a depth of 1-1/4" in it, and iodoform or
napthalene spread over the surface. The following instances
show that mice detected the seed despite the strong smell of
the substance sprinkled over the surface. (Only the first
time the box was put in a given mouse's cage is considered,
since on repeating such a test there is a chance memory
rather than sense of smell rcould cause the mouse to dig.)

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With Mouse 11 two moth balls (napthalene) we;?e crusliej. and
put on the soil surface. The first night the mouse dug
into the box. "but only went to a depth of 1/2", ani there-
fore did not reach the seed, though it seems he must have
smelled them; With Mouse 12 a similar test was carried on,
but in this case one-fourth teaspoonf ul of iodoform was put
in the surface. In one night 4J;J of the seed in the box
were dug up. Again, with Fouse 13 a test similar to that
with House 11, except that the napthalene was placed in a
layer over the seed instead of on the ground sir face, was
carried on. Approximately 5°^ of ^e s66^ were eaten in
one night.

In the field seed spotting on Pilot Knob (P & S 2)
most of the spots were mulched and a few were left unmulched.
Signs of mouse damage were verjr evident in the unmulched
spots, and apparently almost absent in the mulched ones. Two
spots mjLLched in the mouse-proof nursery bed already mention-
ed apparently were not dug into. Ho seedlings came up in
these spots, however , and it therefore is not known whether
the mulching actually prevented the detection of the sown
seed by mice, or whether the debris accompanying the mulch
merely hid the evidence of damage. There appeared to be a
strong probability, however, that the smell of vegetation --
in mulching — might be strong enough and of the right nature

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jjons 3 sd" cfifsiffl -- gnirfolina ni

to deaden the smell of the seeds, and so prevent their de-
tection. To test this point the following sxper.i.nniit *-iras
made:
Re&lilts of P & S No. 8:

A nursery "bed similar to that of P & S 7 was made
mouse proof and sown to 46 seed spots, each with 3° seeds
covered 1/2". Ten spots were left unmulched, and various sorts
and amounts ot mulch were used on the other spots. The nun*
ber of seeds which germinated per spot indicated the effi-
ciency of the mulch in protecting during the period the
spots were exposed to the attack of a mouse turned into the
bed.

The mulch did not prove effective protection, "but
it apparently had a slightly "beneficial effect , at least
when its depth was over 3/4". The following is a comparison
of mulched spots with layers of mulch 3 A" to 1-1/2" deep, ant,'.
unmulched spots. There were ten of each.
Class Seedlings per spot Spots with seedlings

I'ulched VAn. 0, Kax, 5, Av. 1.4 $0$

Unmulched Mi.n. 0. I Sax, 1, Av« .4 40^

All of tilt; umiuiched epcts and 6p^ of the above
mulched s^cts load been dug into by the mouse* No evidence
of digging was found in four of the well-mulched spots,
biro is ib not certain that they were unmolested. The spot

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having the highest number of seedlings (5) had certainly

"been dug into,

Extent of Damage in Field Sowing:

Area Ho. 1 of the field sowing was devoted tc- de-
termining how seriously mice and chipmunks damage seed ---pots*
One-fourth of the spots were caged with wire screens, pre-
venting rodent digging, and the others left uncaged. Hilf
of the area had the seed covered 1/2", and the remainder had
I-1/211 of earth over the sown seed.

Gemination was very poor and for this reason no
conclusive results were obtained. On the area, comprising
1/6 acre, 15 white-footed mice and 6 chipmunks were trapped.
Prom the looks of the seed spots it was judged that 9^/j of
the damage done was caused by white-footed mice and 2/£ by
chipmunks. In the 1/2 M sowing, <)6$ of the spots had "been dug
into at the end of 11 days, while 76$" of the 1-1/2" sowing Imd
been similarlTf damaged in the same time. These figures ap-
ply, of course, to the uncaged spots; there was no damage
in the caged ones, since the screens pror ed very efficient
protection. The germination results are not very sug^ stive,
owing to the general poorness of germination. Even in the
protected spots and the shallow sowing it was very poor.
The number of seedlings per caged and per uncaged spot dif-
fered little. Of the caged spots, 60^ had no germination

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while 71/j of the uncaged spots were without seedlings. The
most seedlings per spot were in an unprotected spot. Ger-
ij4 1 nation was almost an utter failure where 1-1/2" of soil cov-
ered the ceed.

On P & S No. 3j at least 82$, and probably more,
of the seed spots had been dug into by mice or similar ani-
malSj when examination was made July 22, 1912, a month and
a half after sowing.

On P & S No. 4, a count on the north slope showed
86$ dug into and one on the south slope showed fji?$ of the

certainly dug into by rodents. The time of sowing and
of examination were similar to P & S No. 3*

On P & S Ho. 5 1 w&ere the spots were made with a
tamp, and were 3" in diameter arrl lt! to 2" deep, a count on
the north slope showed at least 73$ duS into by rodents, and
one on the south slope showed 76$ molested.
Results of Poisoning 20-30 Acres in Spring, and Sowing Seed
in Fall:

P. & S. Ho. 6 is an experiment in poisoning to rid
a small tract of rodents so that seed could safely be sown on
it. The trial failed. The area was poisoned with strych-
nine-treated wheat on June 15, 1912. The wheat was poisoned
by Dr.. Dea.rbcrn of the Biological Survey, and was distribut-
ed partly "by him and partly under his direct supervision. To

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a "bushel of wheat, 2 ounces of strychnine in the alkaloid
form and 3 pints of tallow were used. (On the lit. Hebo
poisoning, Kraebel gives the folio?/ ing figures: To 5 gal-

j'j-s cf wheat, 20 teaspoonfuls of strychnine and. one quart
of -callow The strychnine and tallow were mixed "before ap-
plying to the wheat, but this was not done in the poisoning
of P & S Ho. 6.) (The poisoning on the Mt. Kebo area w«,8
more severe, since 1 teaspoonful instead of 1/2 teaspoonful
of strychnine was used per quart of wheat.) Since the
wheat was :V>.stributed at the rate of 1 bushel to 20-30 a-
cres, 1 quart to 1-1/2 quarts was used per acre. (In the lit.
He'oj poisoning 5 according to Kraebel, the wheat was distri-
buted L\t -he rate of 2 to 3 quarts per acre.)

Oi.' July 27 most of the wheat seemed to have been
eaten or carried away. One dead mouse was found; some ker-
nels half eaten showed rodent work; seme bird feathers were
found near piles of ™>ieat.

On October 26, 28 and 3°i part of the area was
sown to Douglas fir and western white pine. The sowing of
the 26 tli was examined on the 28th, and one count showed 80;£
to 96^3 of the spots dug into. Another count made nearer
the center of the tract showed 80)£ to 90^ of the spots mo-
lested. This was after two nights. During the same time
four mice were caught in five traps and the bait of the
fifth tiap had been nibbled without springing the trap. On

-11-

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October 30 the sowing of the 2oth was examined. On a
strip through the center of the tiact lOOJi of spots where
seed was covered 1/2" deep appeared to have been disturbed,
while 91/£ of these undoubtedly had been burrowed into,
since seed husks were found on them. In spots similarly
placed but with seed covered lft deep, J2/0 appeared to have
been molested and 38/4 &ad surely been dug into, as shown
by the husks of eaten seeds on the spots. As with the pre-
vious count, this damage was done during two nights after
sowing. As before, in this time four mice were caught in
five traps, and the bait of the fifth trap had been nibbled.
The traps this time were set as near as possible to the cen-
ter of the sowing area, and about in the center of the area
poisoned.

It is evident, therefore, that poisoning a small
area in the early summer cannot be depended upon to rid the
tract of rodents to such an extent that- seed can safely be
sown on the place in the following fall.

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