同种竞争压力对小泡巨鼠贮藏油茶种子行为的作用分析

2002年11～12月，在四川省都江堰地区的亚热带常绿阔叶林内利用人工修建的半自然状态围栏进行实验，研究了小泡巨鼠在有同种竞争存在条件下对油茶种子的埋藏行为。结果表明，小泡巨鼠在有竞争存在条件下，显增加了埋藏油茶种子的量。这一结果支持了“竞争的存在刺激鼠类埋藏”的假说。同时，研究结果表明，小泡巨鼠在有竞争存在条件下，显增加了对埋藏种子的搬运距离，每个贮藏点埋藏种子的数量也有所增加，同时埋藏的生境更多地偏向于遮蔽较好的微生境(草丛底层、灌丛下层)中。这些行为策略有可能有利于种子被埋藏植物的种群扩散。在讨论中，我们还通过比较鸟类和兽类在感觉器官上的差别，分析它们在有竞争存在条件下所采取的不同贮食策略。

Analysis of the Effect of a Conspecific Competitor on the Caching of Oil Tea Seeds by Edward's Rats

Previous research work has shown that some birds cache fewer food items in the presence of a conspecific competitor, but some rats cache more. None of these studies paid attention to the dispersal distances of buried food and the microhabitats where the food was buried. In order to examine the effect of the presence of a conspecific competitor on dispersal distances of buried food and microhabitats where food was buried, an experiment was conducted from November to December 2002. The experiment was performed in two enclosures that were built with bricks in secondary forest in Dujiangyan District, Sichuan Province, China. The climate is sub-tropical. The wall of the enclosures extended 1.3 m above and 0.5 m below ground to prevent subjects from escaping during the experiment. A piece of 8 cm mesh net covered each enclosure to isolate predators from the outside. The subjects used in the experiment were Edward's rats (Leopoldamys edwardsi).The food provided for Edward's rats to eat and bury were oil tea seeds (Camellia oleifera).Each subject was given 50 seeds and 1 night to eat and bury the seeds. The next morning, the number of seeds eaten, buried and dispersed were recorded, as well as the dispersal distances of the buried seeds and their microhabitats. The results showed that in the presence of a conspecific competitor, Edward's rats cached more oil tea seeds, and the mean cache size increased. The dispersal distances of buried seeds was much larger in the presence of a conspecific competitor. Furthermore, in the presence of a conspecific competitor, Edward's rats cached a larger proportion of buried seeds under grass or under shrubs, and a smaller proportion in open ground. We discuss the difference in caching behavior in the presence of a conspecific competitor between birds and rodents. The presence of a conspecific competitor promoted Edward's rats to bury more food, supporting the hypothesis that rats would bury more food in the presence of a competitor. When there were competitors, each rat would share fewer food items. In order to gain an advantage over the others, a subject would cache more food items for later use only by itself. Birds receive information from outside mainly by vision. Since the competitor would notice the cacher caching the food items, which would lead to loss of the buried food items, birds would cache fewer food items to avoid wasting their energy investment. Rodents receive information from outside mainly by olfaction, while vision performs less of a function, especially in secondary forest at night. When facing a competitor, rodents worried less about the loss of buried food items than birds, so they cached more food items. Edward's rats cached oil tea seeds more widely in the presence of a conspecific competitor, which brings an advantage to oil tea. Seeds were buried much farther away from where they were released (or where they dropped on the ground), causing the population of this plant to develop faster and more widely.