Variation in the Caudal Fat Deposit of Microdipodops megacephalus

Abstract

The size of the caudal fat deposit varied seasonally in a population of the dark kangaroo mouse ( Microdipodops megacephalus ). Tails reached their maximum circumference prior to a period of winter inactivity, and were thin in the spring, when mice resumed activity. Juveniles had thinner tails than adults. There was some evidence that tail thicknesses differed between years. Sexes did not differ in tail thickness or rate of increase in thickness. Mice that returned to the study area after winter 1979–80 had thicker tails during the preceding fall than did mice that did not return. Comparison of the adaptations of desert small mammals with caudal fat deposits suggests that small body size, torpor, and a non-granivorous diet are selective factors associated with such fat stores.