Competing seed consumers drive the evolution of scatter-hoarding: Why rodents do not put all their seeds in one larder

Abstract

Competition for food resources amongst animal seed dispersers and pilferers has driven dispersers to increasingly innovative seed-caching methods. We determined cache sizes in the field as well as seed cache recovery ability of a scatter-hoarding mouse, Acomys subspinosus, and compared these results to its seed competitor, the seed predator Rhabdomys pumilio.We found that up to 76% of A. subspinosus caches in the field contained one seed and that A. subspinosus was able to find caches of all sizes equally well under wet and dry soil conditions. In contrast, R. pumilio was able to find caches of all sizes in wet soil conditions but recovery success of small caches  (single-seed) was poor in dry soil conditions. This suggests that scatter-hoarding may have evolved in A. subspinosus as an anti-pilfering strategy. This strategy would likely work best in dry conditions, where cache pilferers have difficulty locating small caches.

Keywords: cache recovery, olfaction, rodent, fynbos, Acomys subspinosus, Rhabdomys pumilio