Scatter‐hoarding and cache pilfering of rodents in response to seed abundance

Abstract

Seed caching and reciprocal cache pilferage play an important role in the coexistence of food‐hoarding animals. Understanding what affects seed caching and how cache pilferage occurs is an important question in seed dispersal ecology. However, tracking seed fate and cache pilferage presents substantial practical difficulties. Siberian chipmunks Tamias sibiricus always remove the entire pericarp when scatter‐hoarding acorns of Mongolian oak Quercus mongolica, whereas wood mice Apodemus peninsulae often store whole acorns in their caches. These differences in behavior provide an opportunity to investigate unilateral cache pilferage of T. sibiricus from A. peninsulae in response to seed abundance. In this study, tagged acorns were released at the peak and end periods of seed rain from Q. mongolica. This allowed us to investigate seed caching and unilateral cache pilferage at different seed abundances. We found that a higher proportion of acorns were cached at lower level of seed abundance (toward the end of seed rain), mainly because T. sibiricus rather than A. peninsulae scatter‐hoarded significantly more acorns at this time. Cache distances decreased with increasing seed abundance, indicating that acorns were cached further away and into smaller caches at lower seed abundance. Unexpectedly, unilateral cache pilferage by T. sibiricus was not significantly influenced by seed abundance—remaining at around 28% during both periods of high and low seed abundance.

Prescribed fire and partial overstory removal alter an acorn–rodent conditional mutualism

“…Too few acorns were cached in our forest floor survival experiment to assess how treatments affected cache recovery. However, cache recovery based on spatial memory may display different trends than cache pilferage, as the two are driven by fundamentally different behavioral processes (Wang et al 2018, Yi et al 2019. We found higher overall survival of artificial caches (24%) than rodent caches (15.7%), consistent with a recovery advantage for cache owners (Steele et al 2011).…”

“…, Yi et al. ). We found higher overall survival of artificial caches (24%) than rodent caches (15.7%), consistent with a recovery advantage for cache owners (Steele et al.…”

“…However, we caution that variation between sites, harvests, and prescribed burns, and lack of fully replicated control sites, constrain the generality of our results. A broader understanding of the implications of silviculturally altered acorn-granivore interactions will require work under a range of conditions imposed by annual variation in acorn mast crop and small mammal population fluctuations; composition of mast-producing species; and in habitats of varying ages and maturational stages (Raybuck et al 2012, Kellner et al 2014, 2016, Lichti et al 2014, Yi et al 2019.…”

Squirrel-Seed Interactions: The Evolutionary Strategies and Impact of Squirrels as Both Seed Predators and Seed Dispersers

“…One species of squirrel that does not perform embryo excision of early germinating acorns appears to have overcome this problem with a suite of other behavioral strategies that allow it to manage the challenge of early germination (Table 2). Although this species is known to larderhoard food for winter hibernation, the relatively solitary species also regularly engages in scatterhoarding and, as a result, contributes significantly to seed dispersal (Wang et al, 2018;Yi et al, 2019b). In China, Siberian chipmunks (T. sibiricus) exhibit the unique behavior of pericarp removal of acorns of Q. mongolica, Q. variabilis, Q. aliena and Q. serrata var.…”

“…Moreover, field evidence showed that whole acorns cached by wood mice, Apodemus peninsulae, were more likely to be pilfered by Siberian chipmunks than acorns that had pericarps removed. Pilferage rates of whole intact acorns were estimated at 28% during both periods of both high and low seed abundance (Yi et al, 2019b).…”