Research On Factors Affecting Seed Hoarding Behavior Of Small Rodents In Yugong Area, Jiyuan, China

In the forest ecological system, small rodents paly a critical role in predating seeds of plants. Meanwhile, because of their food hoarding behavior, rodents act as important seed disperser. Once the buried seeds escape from predation by animals, they may germinate and establish seedlings. Recruitment in many plants needs the aids from dispersal agency from animals, and plants develop some characteristics to attract animal dispersers, for instance, mast seeding, the phenomenon where a population of plants synchronously but intermittently productes a large amount of seeds, while exhibiting low seed production at other times, is common in perennial plants where the seeds are dispersed by scatter-hoarding animals. For the animals which live in forest, they must develop strategies to adapt to the annual changes in food quantity. Some rodents can affect seed dispersal and regeneration of plants by eating or scatter hoarding seeds. Therefore, the scatter hoarding behavior of small rodents has attracted the attention of many ecologist who commited to the study of co-evolutionary between plants and animals. To study the influential factors on scatter hoarding, community composition and its variation of local rodents were investigated as well as the seed dispersal and hoarding by rodents in semi-naturl enclosures in State-owned Yugong Forest Farm in Jiyuan, Henan province, China. We also studied the effects of seed abundance on food hoarding behabior of Western Chipmunk(Eutamias sibiricus) and the key factors which affect the capacity of Apodemus peninsula to discover scatter-hoarded seeds. The main results and conclusions of this research are showed below:1) It was found that Apodemus peninsula, Niviventer confucianus were the main rodent species in Yugong region. The trap success of the rodents was high in 2009 than that in 2010 in study area, the population of the main rodent species was different during seasons and habitats, not significantly, and the quantity of main rodents were lower in spring than that in summer and autumn; the number of them was higher in shrub;2) the seed production and the constitute of seed rain of Cork oak varied significantly between years, the intact seeds were the majority in 2008, while the aborted seeds were the most in 2009. The median survival time of released nuts in 2008 and 2009 were 22.700 d and 8.825 d, respectively, the mean transporting distance of nuts of Cork oak was significantly shorter in 2008 than that in 2009, rodents tended to hoard more nuts of Cork oak scattered in 2008 than that in 2009. Our results indicated that mast seeding increased the possibility of nuts escaping from predating, and then benefit plant regeneration under predator satiation.3) In the experiment of effects of abundance of nut of Juglans regia on hoarding behavior of Western Chipmunks, the results indicated that Chipmunks mainly scatter hoaded the seeds of walnut, the number of seeds cached by Chipmunks increased with increasing of seed abundance. This indicated that higher seed abundance would stimulate the rodents scatter hoarding more seeds rather than predating.4) In dry condition, the seed discovery capacity of Apodemus peninsulae was significantly affected by blocking the visual signal. Moreover, the seed discovery rate was significantly increased with increasing of soil humidity; the number of seeds found by Apodemus peninsulae was significantly increased with the increasing of soil humidity.In short, seed abundance is an important factor affecting scatter-hoarding behavior of small rodents, which tend to scatter-hoard more seeds in mast seeding years, which indicated that mast seeding increased the possibility of nuts escaping from predating, and then benefit plant regeneration under predator satiation. Rodents'discovery rate of buried seeds significantly reduced under dry condition, the discovery rate of buried seeds by rodents was significantly related with the increasing of soil humidity.