Does scatter-hoarding of seeds benefit cache owners or pilferers?

The scatter-hoarding behavior of granivorous rodents plays an important role in seed dispersal and seedling regeneration of trees, as well as the evolution of several well-known mutualisms between trees and rodents in forest ecosystems. Because it is difficult to identify seed hoarders and pilferers under field conditions by traditional methods, the full costs incurred and benefits accrued by scatter-hoarding have not been fully evaluated in most systems. By using infrared radiation camera tracking and seed tagging, we investigated the benefits and losses of scatter-hoarded seeds (Camellia oleifera) for 3 sympatric rodent species (Apodemus draco, Niviventer confucianus and Leopoldamys edwardsi) in a subtropical forest of Southwest China during 2013 to 2015. We established the relationships between the rodents and the seeds at the individual level. For each rodent species, we calculated the cache recovery rate of cache owners, as well as conspecific and interspecific pilferage rates. We found that all 3 sympatric rodent species had a cache recovery advantage with rates that far exceeded average pilferage rates over a 30-day tracking period. The smallest species (A. draco) showed the highest rate of scatter-hoarding and the highest recovery advantage compared with the other 2 larger species (N. confucianus and L. edwardsi). Our results suggest that scatter-hoarding benefits cache owners in food competition, supporting the pilferage avoidance hypothesis. Therefore, scatter-hoarding behavior should be favored by natural selection, and plays a significant role in species coexistence of rodent community and in the formation of mutualism between seeds and rodents in forest ecosystems.