UX'Sa. \islK-r l"l(i). Joined with this ability was 

 long-range vision to discern the approach of danger 

 from a distance. Coyotes could not run as fast as 

 prongliorn, but since the pronghorn usually ran in 

 wide circles, the members of a pack of coyotes would 

 sometimes run in relays until the pronghorn fell 

 exhausted. 



Rodents and lagomorphs constitute the other 

 principal groups of mammals. Ground squirrels, 

 pocket gophers, mice, and jack rabbits are common 

 nearly everywhere and sometimes reach plague pro- 

 portions. Prairie dogs form towns, some in former 

 days large enough to cover several square miles, with 

 each animal feeding on the grasses and herbs only in 

 the vicinity of his own burrow. Prairie dogs are most 

 numerous on the Great Plains where the grasses are 

 shorter, and a century ago they probably numbered 

 in the billions. They as well as other species of ro- 

 dents have numerous predatory enemies such as 

 coyotes, badgers, ferrets, foxes, weasels, owls, and 

 rattlesnakes. They have good vision, however, and 

 quickly plunge into their extensive underground bur- 

 rows at the approach of danger (Koford 1958). 



Jack rabbits, other small mammals, prairie chick- 

 ens, as well as most of the small birds, grasshoppers, 

 and other insects rely considerably on their well 

 developed protective coloration — they freeze in the 

 deep grass to escape notice of predators. If the preda- 

 tor comes too close, they take to running, jumping, 

 or flying with such a burst of activity so as to startle 

 the intruder momentarily and give them a head start 

 in their flight. 



The development of hopping locomotion among 



\ 



0i4a 





Grassland biome 329 



