The Cache Recovery Mechanism Of Squirrels (Sciurus Vulgaris Mantchuricus)

From September 2005 to April 2006, this study was designed to investigate the recovery mechanism of cached food by squirrels (Sciurus vulgaris mantchuricus) in the captivity, in the Longying wildlife feed lot, in the suburb of Harbin. To know the recovery mechanism more exactly and clearly, we conducted some experiments under control. The results showed as follow:1 The spatial memory ability and pilferer is the main tool of squirrels to recover cache. In little scale, squirrels mainly depend on pilferer to recover cache. In large scale, squirrels mainly depend on spatial memory ability to recover cache. All the factors to be concerned, spatial memory ability play a more important role than pilferer in cache recovery of squirrels in nature.2 The pilferer of squirrels is sharp. Depend on sharp pilferer, squirrels could easily find the seeds of Korean pine(Pinus koraiensis) buried in soil with the depth of 8 cm, which is deepe than the main burial depth (2～5 cm) and deepest burial depth (7 cm) of the seeds of Korean pine in this experiment, and also deeper than the mean depth 15.8cm of the seeds of Korean pine in Liangshui nature reserve. Squirrels could easily find the seeds of Korean pine buried in soil with the depth of 16～20 cm, which is deeper than the mean burial depth 15.8cm of the seeds of Korean pine in Liangshui nature reserve. So we could conclude that the pilferer play an important role in cache recovery of squirrels, especially in recovery other squirrel's cache. However, the pilferer could only be used to recover cache in little scale, if the distance of cache is more than 50 cm, the cache is hard to be found by the pilferer of squirrels.3 Squirrels could depend on spatial memory ability (mainly by memorize the spatial pattern in a suitable scale around the cache) to recover their cache. Squirrels could exactly remember the orientation of cache and spatial pattern around the cache, it also could remember the size and direction of soil container, but it could hardly remember the color of soil container and planar difference of soil. Squirrels could remember the orientation of cache about 15 days in this study, but should be longer in nature.4 Compared with the spatial memory ability and pilferer, the trail made by squirrels when cached the seeds is nearly useless for the recovery of squirrels (include hoarder and nonhoarder).