The Nevada Mouse Plague, 1907-8. 
In December, 1907, we told the story of the 
plague of field mice which had appeared dur¬ 
ing the previous summer in Humboldt Valley, 
Nevada. The mice were first seen in noticeable 
numbers in ^lay, 1907, and by . October their 
numbers had so greatly increased that the yield 
of hay had been re¬ 
duced by one - third, 
potatoes and wheat 
crops were quite gen¬ 
erally destroyed, many 
alfalfa fields were ruin¬ 
ed, and the entire de¬ 
struction of this, the 
chief crop of the val¬ 
ley. was threatened. In 
November the animals 
had so greatly increased 
that it was estimated 
that on many large 
ranches there were from 
8,000 to 12,000 mice to 
each acre. The animals 
burrowed down about 
the alfalfa plants, fol¬ 
lowed the roots along, 
and ate them so that 
they either killed or 
seriously injured the 
plants. They attacked 
the roots of trees, in¬ 
juring or destroying or¬ 
chards, killed most of 
the young shade trees 
planted along the irri¬ 
gating ditches, and even 
completely girdled and 
killed large poplars. In 
the following winter 
they stripped the bark 
from the small willows, 
and even the grease- 
wood. The ground was 
traversed in every direc¬ 
tion by their tunnels and 
honeycombed by the entrances to the burrows. 
Of course, the ranchman tried to fight them, but 
'in an unintelligent spasmodic way, using wheat 
treated with a strong solution of yellow phos¬ 
phorus in carbon bisulphid, a poison which was 
cheap and effective for mice, but just as effec¬ 
tive for birds, besides being inflammable and 
explosive. Great numbers of California quail 
and other birds were destroyed by this poison¬ 
ing. On one occasion sixty-seven horned larks 
were found dead on a small area, and many 
skunks and cats were killed as a result of eat¬ 
ing mice poisoned with phosphorus. Cases of 
fatal poisoning of live stock occurred. 
-A.t last the Biological Survey, as told in a 
Farmers’ Bulletin by Stanley E. Piper, by sys¬ 
tematic experiments on the Rodgers ranch, 
proved that mice could be effectively destroyed 
in the winter by alfalfa hay, poisoned with 
strychnine. Meantime predaceous birds and 
mammals had not been idle and had greatly re¬ 
duced the numbers of the mice. Moreover, they 
began to die without known cause, perhaps 
owing to a lack of food and severe cold weather. 
The most efficient poison, besides being the 
safest, is strychnia sulphate. It is soluble in 
water and so is readily prepared. Alfalfa hay, 
the fresher the better, chopped into short 
lengths, or the fine leaves and blossoms from 
the base of stacks, could be used. The material 
should be placed in a large metal receptacle to 
the amount of thirty pounds, and this sprinkled 
with three gallons of fresh water and well 
mixed with a pitchfork. One ounce of strychnia 
sulphate dissolved in two or three gallons of 
water by heating in a closed vessel should be 
sprinkled over the already dampened hay, and 
well mixed until all the moisture is taken up. 
This is now put in sacks and is ready for use. 
A small pinch of this hay, about a teaspoonful, 
should be placed near the entrance of each bur¬ 
row, where it will be found and eaten by the 
mice. Wetting the dry alfalfa hay with water 
freshens it and makes it attractive to the field 
mice, especially so in winter. Green alfalfa was 
also used with very great success, as was 
crushed wheat. The destruction of the mice 
by these means was very great, but of course 
a proportion still remained uninjured. By going 
over the fields in which the holes of the mice 
were so numerous with a brush drawn by horses, 
the burrows at the surface were obliterated, and 
a little later it was easy to see what holes had 
been reopened and so were occupied. 
In a case of this kind it was important to 
remove—preferably by burning—all growth of 
grass, weeds and brush 
in which mice might 
hide. Dogs were found 
effective enemies in 
fighting the mice and 
learned to follow the 
plow and kill them as 
they were turned out 
of their burrows. The 
services rendered by 
hawks, owls, gulls, 
crows, ravens, herons 
and shrikes among 
birds; and by skunks, 
coyotes, foxes, weasels, 
badgers and wildcats 
among mammals, are 
the greatest benefit. 
It is estimated that 
the loss in the Hum¬ 
boldt Valley from this 
cause was not much less 
than $300,000. Further 
up the valley, in land 
less of which had 
been cultivated, another 
plague of mice occurred, 
but the damage was 
much less. In the Car- 
son Valley there was 
great destruction of the 
alfalfa crop by mice. It 
was shown that the fe¬ 
males produced from 
six to ten young at a 
birth, and the increase 
if unchecked would have 
been something beyond 
belief. Mice are very 
prolific, each pair producing from four to six 
litters of six each during the long breeding sea¬ 
son from March to November. 
The lesson of this plague of mice is that a 
constant warfare on these rodents must be 
waged by each farmer. 
Beavers Repairing a Dam. 
Chicago, Ill., March 27 .— Editor Forest and 
Stream: The first illustration given herewith 
shows a beaver dam about six hundred feet long 
across a creek in Northern Michigan, thus form¬ 
ing out of a small spring-supplied lake a large 
lake of about sixty acres, having in it two large 
beaver houses and a third in course of con¬ 
struction. They are at the far side of the lake 
and are not visible in the picture. They were 
probably placed there to guard against being 
taken out by the ice in the spring time. Notice 
THE BEAVER DAM BEFORE AND AFTER IT HAD BEEN CUT. 
