STACKING OF SEEDS CHANGES SPOILAGE DYNAMICS OF FOOD CACHES OF THE BANNER-TAILED KANGAROO RAT (DIPODOMYS SPECTABILIS)

Abstract

We report a previously undescribed seed-storing behavior of banner-tailed kangaroo rats (Dipodomys spectabilis) that reduces losses to microbes. D. spectabilis cuts upper stems of the grass Sporobolus cryptandrus into 3-to 5-cm sections that we refer to as seed stems. Seeds within these seed stems remain attached to their rachis and are protected by an enveloping leaf. Most seed stems are bundled together tightly in packs of about 50 to several hundred individual stems and jammed vertically into cul-de-sacs excavated in the walls of their burrows. This behavior reduces rate of infection of seeds by fungi and also may reduce number of seeds pilfered by arthropods. Furthermore, compared with seeds of S. cryptandrus housed in middle sections of seed stems, those housed in the ends had a higher rate of infection. Simulated seed stems of wheat straw containing seeds of white millet (Panicum miliaceum) had a lower rate of infection and fewer species of fungi than seeds only protected by wire mesh. Seeds closer to the top of the simulated seed stems were more likely to be infected and had more species of fungi. Community structure and dynamics of microfungi also appeared affected by the protective layering of seed stems. We suggest that D. spectabilis manages the structure, and perhaps dynamics, of communities of microbes within their food caches by modifying position, location, or organization of food items.Key words: caching behavior, Dipodomys spectabilis, kangaroo rat, storing strategies Food storing occurs in a variety of ways by a variety of organisms (Smith and Reichman 1984;Vander Wall 1990). Banner-tailed kangaroo rats (Dipodomys spectabilis; Heteromyidae) are predominantly seed-storing rodents that construct large underground burrow systems where they cache vast amounts of food (Mun and Whitford 1990;Vorhies and Taylor 1922). These caches usually attract a diversity of microbes (Hawkins 1992; and microarthropods (Hawkins and Nicoletto 1992;Seastedt et al. 1986).While studying populations of microfungi that inhabit caches of D. spectabilis at Sevilleta National Wildlife Refuge, Socorro County, New Mexico, we happened on * Correspondent: jherrera@truman.edu caches of food containing large numbers of cut stems containing seeds of the sand dropseed (Sporobolus cryptandrus-Herrera 1996). These seed stems were bundled tightly upright and squeezed into cul-desacs dug in walls of the burrow (Fig. 1).Although we suspect that cutting and carrying stems containing seeds of S. cryptandrus allows D. spectabilis to transport seeds efficiently to their burrow, we were interested in determining why D. spectabilis organizes and places seed stems upright in their burrow. We believe that careful organization of the seed stems of S. cryptandrus is time consuming and energetically costly and suspect the existence of an equally powerful counterselective advantage(s) to the food-storing behavior of the rodent. We investigated whether seeds of S. cryptanDownloaded from https://academic.oup.

Kangaroo Rats Remodel Burrows in Response to Seasonal Changes in Environmental Conditions

“…High levels of fungal infections in seed caches occur within mounds after rainfall . While banner-tailed kangaroo rats may prefer slightly moldy seeds, they avoid eating very moldy seeds and actively manage seed caches to reduce major fungal infections Reichman et al 1986;Frank 1988;Herrera et al 2001). Massive fungal contamination of seed caches with mycotoxins are implicated in the near-extirpation of banner-tailed kangaroo rats following a large rainfall event of 129 mm in Arizona (Valone et al 1995), indicating that significant cache loss can greatly impact fitness.…”