Food availability and animal space use both determine cache density of Eurasian red squirrels

PLoS One. 2013 Nov 12;8(11):e80632. doi: 10.1371/journal.pone.0080632. eCollection 2013.

Abstract

Scatter hoarders are not able to defend their caches. A longer hoarding distance combined with lower cache density can reduce cache losses but increase the costs of hoarding and retrieving. Scatter hoarders arrange their cache density to achieve an optimal balance between hoarding costs and main cache losses. We conducted systematic cache sampling investigations to estimate the effects of food availability on cache patterns of Eurasian red squirrels (Sciurus vulgaris). This study was conducted over a five-year period at two sample plots in a Korean pine (Pinus koraiensis)-dominated forest with contrasting seed production patterns. During these investigations, the locations of nest trees were treated as indicators of squirrel space use to explore how space use affected cache pattern. The squirrels selectively hoarded heavier pine seeds farther away from seed-bearing trees. The heaviest seeds were placed in caches around nest trees regardless of the nest tree location, and this placement was not in response to decreased food availability. The cache density declined with the hoarding distance. Cache density was lower at sites with lower seed production and during poor seed years. During seed mast years, the cache density around nest trees was higher and invariant. The pine seeds were dispersed over a larger distance when seed availability was lower. Our results suggest that 1) animal space use is an important factor that affects food hoarding distance and associated cache densities, 2) animals employ different hoarding strategies based on food availability, and 3) seed dispersal outside the original stand is stimulated in poor seed years.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Feed*
  • Animals
  • Biomass
  • Feeding Behavior*
  • Pinus
  • Population Density
  • Population Dynamics
  • Sciuridae / physiology*
  • Seeds
  • Trees

Grants and funding

This work was funded by Forestry Industry Research Special Funds for Public Welfare Projects of China (200904012) and the National Natural Science Funds of china (31172100, 30970372). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.