36 The Mammals of Colorado 
efforts. Here the animals were destroyed by driving them into 
an enclosure, and they were then killed with clubs by men on 
foot. The rabbits were driven to the place by a large number 
of men, both on foot and on horseback, who began opera- 
tions away from the entrance and gradually worked toward 
it, driving the rabbits ahead of them until they were forced 
into the enclosure. This was of wire netting, and usually 
with wings extending for a considerable distance on either 
side; at one drive these wings covered a space of seven miles. 
In 207 drives from 1888 to 1897 inclusive, 494,634 rabbits 
were killed. These figures are from the Biological Survey 
Bulletin on the Jack Rabbits. Drives and hunts have also 
been held in other States besides those mentioned, but it is 
hardly necessary to describe them particularly. 
Like the Snow-shoe Rabbit, Jack Rabbits are subject to 
epidemics, which at times destroy large numbers of them. 
We do not find much information as to their nature, Preble 
being the only one who gives us any report about it, at least 
of late. He examined a number of Varying Hares (Lepus 
americanus) in the upper Mackenzie region which had died 
of the disease, and found the throat and lungs much in- 
flamed, the viscera were in an excessively moist condition, 
and the skin and flesh were very dry, and separated with 
difficulty. These epidemics occur every five to seven years. 
They have been known in Colorado, but do not affect the 
whole State at the same time apparently, being seemingly 
local in their effects. There was one in the San Luis Valley 
two or three years ago; and in Grand and Routt counties, 
in the spring and summer of 1907, it was reported to me 
that the rabbits had been killed off by some disease; certainly 
they were very scarce all through that season, when I was 
collecting there, and especially anxious to get good series of 
the rabbits; Cottontails were fairly plentiful, but Jacks were 
but seldom seen. 
