182 WATCHED BY WILD ANIMALS 
development of the pronghorn in the desert 
regions—the ability to do without water for days 
at a time. 
The food of the pronghorn is sage, grease- 
wood, sometimes cactus, and, on the desert, 
broomrape. I do not recall ever seeing him 
eat grass. In the extremely arid regions of 
the Southwest the local flocks, in common with 
mountain sheep and other animals of the desert, 
have developed the habit of doing without water 
for days—sometimes for a period of two weeks 
or longer have no other moisture than that fur- 
nished by the plants eaten. 
When the young antelope are about three 
weeks old they appear to have full use of their 
legs and usually follow the mother in feedings 
and fights. At this time numbers of mothers 
and youngsters collect and run together. They 
are thus enabled to give mutual aid and to 
withstand coyotes and other enemies better. 
Sometimes under dangerous conditions the 
young are left behind while some of the mothers 
go for water, and on their return the remaining 
ones go. Just why this mutual aid is not 
practised while the young are almost helpless 
is not clear. 
In early autumn all ages and sexes unite and 
commonly run together, often in large flocks, 
throughout the winter. The youngsters often 
