BANTA, M.R.: The effects of temperature on seed movement in the caching rodent, Merriam’s kangaroo rat

The desert-dwelling rodent Merriam’s kangaroo rat (Dipodomys merriami) is known to manage cached seeds. Studies have documented individuals moving cached seeds within burrows or a testing arena. These studies suggest that kangaroo rats move seeds to areas of high relative humidity. Two hypotheses have been offered to explain this behavior: an attempt to enhance water uptake by seeds that the kangaroo rat then obtains when feeding, and an attempt to place seeds in a microhabitat conducive to the growth of beneficial molds. Temperature as well as humidity can vary within kangaroo rat burrows, yet a connection between seed movement and temperature has not been explored. In this study, seed movement by kangaroo rats was studied under constant humidity and variable temperature. Kangaroo rats that were either water-stressed or had ad lib water were allowed to move among eight chambers held at temperatures ranging from 10 to 38 &deg C. Absolute humidity was constant in all chambers. Each chamber contained 4.0 g of barley seeds at the beginning of each trial. All the water-stressed animals visited all eight chambers and all moved seeds. These animals tended to move seeds into the chambers where they spent the most time. Five of the eight animals that were not water-stressed never left the chamber they started in, regardless of temperature. Those that did visit all eight chambers also moved seeds to the chambers where they spent the most time. Most of the animals spent the majority of their time in the warmest (38 &deg C) chamber and also moved many seeds into this chamber. Keeping seeds nearby as individuals track ambient temperature in their burrows for energetic savings could facilitate cache guarding in an environment where food resources are limited and competition is high.