Food Hoarding Behavior Of Rodents In Xishuangbanna Area, Yunan, China

Abstract:Food hoarding is an important component of the adaptive strategies of many rodents when short on food resources in long-term or short-term. There are two major forms of seed hoarding:larder-hoarding and scatter-hoarding. The benefits derived from hoarding food include improving an individual's chances of surviving a period of food scarcity, improving an animal's competitive status when foraging for limited resources, and insuring a continuous, even flow of food to young in the reproductive season. Some rodents scatter hoard seeds, it is a key stage of plant regeneration loop. Many factors, especially seed characteristics, such as pericarp thickness, nutritive material et al play a key important part in hoarding decision of rodents. Some rodents can affect the seed dispersal and regeneration of plants by eating or scatter hoarding seeds, which are depend on the defence and nutritive characteristics of seeds. Therefore, there is a mutualism interaction between rodents and plants about seed eating and dispersal, and which has attracted the attention of many evolutionary biologists and field ecologists.Buff-breasted rat (Rattus flavipectus), and Chinese White-bellied rat (Niviventor confucianus), are dominant rodents species in Xishuangbanna area. They may affect seed dispersal and seedling recruitment of seed trees by eating or hoarding seeds in Xishuangbanna area. Seeds of (Pittosporopsis kerrii) and (Lithocarpus truncatus), which are common tree species in the tropical rain forest of this area, with greatly varied seeds in size, endocarp thickness and caloric value, were used as food item in our experiment. The main research questions centered on difference of seed morphological and nutritional traits, seed hoarding behaviors of the two common rodent species including such factors as predation pressure, competition, and field experience, and their subsequent effects on seed dispersal, seedling recruitment and forest regeneration. The objectives of our experiment were:1) to study seed hoarding behavior of common rodent species, and the mutualism interaction between these rodent and tree species about seed eating and dispersal; 2) to study the influence of the different defence and nutritive characteristics of forest seeds to seed dispersal and forest regeneration; 3) to offer reasonable suggestions and data for effect of competition and coevolution on rodents eating and hoarding seeds. The main results included the following points.1) There were 127 individuals of 10 species small mammals trapped. The average rate of small mammals captured was 6.05%. The N. confucianus and R. flavipectus were the most dominant species of the community of small mammals in study area. In the seven different habitats, the species diversity index in the tropical rain forest was the highest (H'= 1.91); the evenness in the tropical lower montane evergreen broad-leaved forest was the highest(E'= 0.95); the dominance in the tropical seasonal moist forest was the highest (D= 0.94). There was none of small mammals in the rubber forest. The highest population density was found in dry season.2) R. flavipectus hoarded food only in larder form. On the second day,20.8% seeds of P. kerrii and 39.2% seeds of L. truncates were larder hoarded, the difference were marked (Wilcoxon test, second day:P=0.047); 4.2% seeds of P. kerrii and 0.8% seeds of L. truncates were consumed in situ, the difference were marked (Wilcoxon test, second day:P=0.109), respectively. Simulated pilfering of stored food enhanced food hoarding behavior of rodent, more preferred seeds of L. truncates were larder hoarded (Wilcoxon test, P= 0.008). Our result indicated that seeds size and coat thickness would affect decision making in food hoarding and consumption by rodents.3) In the semi-natura enclosures, R. flavipectus hoarded food in larders only, whereas N. confucianus showed larder hoarding and scatter hoarding at the same time. Intraspecific competition strengthened both the R. flavipectus (IS:P= 0.021; EN:P= 0.023) and N. confucianus (IS:P= 0.045; EN:P= 0.004) added the number of P. kerrii seeds which intact in situ or hoarded in larders. The influence of interspecific competition on food hoarding behavior of R. flavipectus was not distinct, however, was conspicuous to N. confucianus (AS:P= 0.016; EN:P= 0.018).