DIXON — RODENTS IN IMPERIAL VALLEY 
143 
On account of numerous breaks in the canals caused by the burrows 
of various rodents, including the muskrat, the ditch tenders and some 
of the irrigation companies consider muskrats as pests, and often men 
are hired or paid a bounty to trap the animals. The bounty is paid 
not on the muskrat^s head but on his tail so as not to detract from the 
value of the pelt. There is no gainsaying the fact that muskrats do 
cause a certain amount of damage. However, the evidence indicates 
that the damage has often been exaggerated, and investigation has 
shown that many of the breaks in the canals were not due to muskrats 
at all. In one instance an extensive break said to have cost upwards 
of five thousand dollars was widely reported to have been caused by 
muskrats, but Mr. Rouse, chief engineer of the Imperial Irrigation 
District, assures me that this particular break was really due to cracks 
in the soil of the canal bank and not to muskrats at all. However, 
two out of fourteen of the mutual water companies In the valley do 
pay a bounty of twenty-five cents on muskrat tails. 
Practically all of the professional trappers wait until December, 
when fur is prime, before they start trapping muskrats. As one trapper 
said: “It doesn’t pay to trap a muskrat in August for twenty-five 
cents when one can get $1.50 for the same animal in January.” District 
number four, which is the smaller of the two districts paying bounty 
on muskrats, covers over 20,000 acres and has 133 miles of canals 
and waterways. In twelve months during 1919-20 this district, ac- 
cording to their secretary, paid a twenty-five cent bounty on 2395 
muskrats. It is obvious that owing to the high prices of fur, nearly 
all of these muskrats would have been trapped, bounty or no bounty. 
One outstanding feature of muskrat control is seen in the fact that the 
market price is much more potent in the reduction of muskrats than 
the bounty system, and this is true even during years when fur is low 
in price. After careful investigation and consideration of all the fac- 
tors concerned, it is believed by the writer that the value of the musk- 
rats’ pelts at least equals, and probably exceeds the damage done by 
these rodents in Imperial Valley. 
The Imperial Valley pocket gopher constitutes the real rodent 
problem in the delta region. Fifteen years ago gophers occurred in 
very small numbers over small but widely scattered areas of the valley. 
This species was then so rare that museums had difficulty in securing 
even a few specimens. Today hundreds could be secured in almost 
any part of the irrigated sections. What has been the cause of this 
remarkable increase? The writer believes that the answer to this 
