Sex differences in repeatability of food-hoarding behaviour of kangaroo rats

Abstract

Many animals store food in small, widely dispersed scatter hoards or in large larder hoards in burrows or other centralized locations. Kangaroo rats (Dipodomys spp.) show an unusual amount of variation in food-hoarding behaviour both between and within species. I used laboratory trials to characterize individual variation in food hoarding by two species of kangaroo rats, Merriam’s kangaroo rats, Dipodomys merriami, and Ord’s kangaroo rats, Dipodomys ordii. Trials were done in arenas with sites for scatter hoarding and larder hoarding, and individuals were tested twice to assess the repeatability of their behaviour. I also removed larder hoards or scatter hoards from some subjects to test their response to simulated cache theft. Males of both species were much more repeatable than females in larder-hoarding propensity, and this was due to greater variation in mean values between males as well as greater variation between trials for individual females. For Merriam’s kangaroo rats, males were less likely to replace lost larder hoards than were females, but the reverse was true for Ord’s kangaroo rats. Sex differences in repeatability of food-hoarding behaviour were consistent with the possibility of alternative mating strategies in male kangaroo rats, while differences in response to cache pilferage between males of the two species were consistent with differences in aggressive behaviour associated with body size. This study of kangaroo rats illustrates the importance of behavioural plasticity as a dimension of personality that may differ in males and females.