Intraspecific Pilferage And Pilferage Avoidance In Sciurotamias Davidianus

Food-hoarding is an important adaptive behavior of animals to cope with seasonal shortage of food,which is beneficial for fitness of both individuals and population.Food pilferage by conspecific and heterospecific is one of the causes of food loss.Reciprocal pilferage hypothesis:that each individual involved in the "hoarding-pilferage" system is both hoarder and pilfer,and animals keep high intensity of scatter hoarding under the conditions of high pilferage because they can compensate for food loss through pilfering from others.The reciprocal pilferage hypothesis provides a new perspective to explain the evolution of scatter-hoarding behaviour in food hoarding animals in which individuals are solitary but have overlapped home ranges.However,there is a lack of experimental evidences in matters of reciprocal pilferage hypothesis.Sciurotamias davidianus is a good model to test the reciprocal pilferage hypothesis because individuals live in solitary with overlapped home ranges and primarily hoard plant seeds in scatter.In this study,I tracked seed hoarding and pilferage(nuts of Juglans regia)between paired squirrels using far-infrared camera traps in a semi-natural enclosure(50 m × 40 m).I wanted to know how individual squirrel shared food sources and pilferage each other.For each individual,we tested:whether food loss pilfered by other individuals could be compensated by pilfering from others,harvesting from seed sources,or both of the two ways.The reciprocal pilferage hypothesis was supported if proportion of food pilfered from others is not less than that pilfered by others.I found that(1)there was no significant difference between the rate of pilferage from others and rate of pilferage loss by other individuals,suggesting that individuals can make up for the loss of food by pilfering food from others;(2)the proportion of foods harvested from the seed sources is higher than that of food loss pilfered by others among S.davidianus which suggest that S.davidianus are more likely to compete for food sources than steal others' stores in high pilferage pressure;(3)the total food harvested from seed sources and pilfered from others was too much more than food loss pilfered by other individuals,suggesting that S.davidianus compensated for food loss both by competing for food sources and pilfering from others.(4)in the face of conspecific competitor,both male and female S.davidianus scatter hoarded more seeds to reduce the possibility of pilferage.In presence of a higher pilferage,female S.davidianus reduced food intake and repeatedly removed seeds to protect food and avoid pilferage.Male S.davidianus are more likely to eat seeds to occupy food resource.These results show that in the face of high pilferage loss,S.davidianus not only compensates for food loss through reciprocal pilferage between individuals,collecting more food from the food resources to take advantage of the competition,increasing eating and/or repeatedly changing cache places.We propose the hypothesis that scatter-hoarding animals will not only pilfer others' foods,but also increase the use of food sources to make up for food loss under the conditions of high pilferage.This study provides experimental evidence to the reciprocal pilferage hypothesis,and references for the evolution of scatter-hoarding and pilferage avoidance behaviour in food hoarding animals.