ANIMAL BEHAVIOR — WALKER 285 



animals merely utilize whatever natural shelter is available. Others 

 exercise considerable ingenuity to construct a fairly definite type of 

 home. 



Prairie dogs build a very definite type of home. It consists of a 

 burrow that may go 15 feet or more almost straight down into the 

 ground with 2 or 3 small chambers at the end. One of these cham- 

 bers is the real nest ; another is a little toilet room ; sometimes there 

 is a spare room ; and 2 or 3 feet below the entrance of the burrow is 

 a little shelf which is used as a sentry station. 



The plains prairie dog usually heaps up a volcano-shaped cone 

 at the entrance of the burrow. The entrance is at the top of the 

 cone. This arrangement prevents water from getting into the burrow 

 should the land be flooded by heavy rain. The little fellows can 

 sit on the crater's rim or inner slope. If alarmed they merely tumble 

 into the burrow, disappearing in an incredibly short time. The 

 manner in which they maintain this crater is particularly interesting. 

 Earth is pushed and kicked out of the burrow and is gradually built 

 up around the entrance. If it is necessary to build the crater rim 

 higher and soil is not being brought up out of the burrow, they go to 

 the outer base of the cone, dig earth loose with their forefeet and 

 teeth, kick it backward with their hind feet up toward the center of 

 the cone and then turn around and push the loose soil with their hands 

 and chests. When the loose soil is finally in place, they pat it with 

 their forefeet and tamp it very firmly with their noses. The nose 

 marks can regularly be seen in fresh, well-kept prairie-dog burrows. 



It is particularly amusing to see prairie dogs working the first thing 

 in the morning after a heavy rain. Almost every individual of the 

 colony is industriously cleaning out its burrow or repairing its cone, 

 pushing the soil into place and tamping it with its nose. In captivity 

 they are fascinating to watch for they are active by day, and if they 

 have not been persecuted they soon become friendly and go about 

 their everyday lives as though they had no spectators. 



Moles {Scalopus, Talpa, and other genera) are related to the 

 shrews {Sorex and related genera) and inhabit North America, 

 Europe, Africa, and Asia. Most people who live in their range know 

 these animals by their work; but very few persons have actually seen 

 them at work. This is because moles spend almost their entire lives 

 a few inches under the surface of the ground burrowing in search 

 of insects. Their burrows appear generally at the surface of the 

 ground as raised ridges of earth, which may be annoyingly conspicu- 

 ous when they cross well-kept lawns. This burrowing is really a 

 process of forcing upward and to the sides the earth loosened by 

 the animal as it forces itself ahead, digging to the right and left 

 with its broad spadelike front feet armed with long, sharp, straight 

 claws and lifting the forepart of its body when it wedges itself into 



