Caching and Recovery of Food by the Western Fox Squirrel

Abstract

Caching of seeds by rodents for future food supplies is recognized by wildlife managers, foresters, nurserymen, and others to be important in plant reproduction. If the entire crop is consumed, reproduction is prevented but if the crop is stored though not all used by the rodent harvesters, plant reproduction may be encouraged by the seed being protected through the winter from normal exposure to severe climatic conditions (Shaw, 1936). Olmsted (1937) has pointed out that, in Connecticut, black oak (Quercus velutina) invades many communities through burial of its acorns by More knowledge is needed of the caching habit and its effect on forest and other vegetation. Of the many forest-dwelling rodents, probably none is of greater significance to their environment than the larger tree squirrels. Red squirrels and most small ground-dwelling rodents gather many seeds into relatively few hoards, but the larger squirrels make many caches, each of one or a few nuts. This wide scattering and planting, if in suitable seed-beds, may at times be a desirable factor in perpetuating the forest. These squirrels, however, need large quantities of food to sustain them, especially as they do not hibernate through the long winters. They depend heavily on the fruit of commercially important hardwood species such as oaks, hickories, walnuts, beech and formerly, the American chestnut. The rapidity with which these nut crops are cleaned up from the forest floor is almost phenome'nal. Hahn (1908) describes the disappearance of a very large acorn crop on the Farm of the University of Indiana in the autumn of 1906, when gray squirrels were also very abundant. He estimated that each of the large white oaks produced from two to eight thousand acorns during that season. Eighty acres [were] heavily wooded with white oaks and nearly a hundred acres more [had] a considerable growth of these trees. Before November 1, the immense crop of acorns had been so completely garnered by the squirrels that none were in sight on top of the leaves and only an occasional one could be found bythe most careful search. In the long run, the fate of the seed crops controls that of the forest. In the fall of 1928 I studied the life history of the western fox squirrel (Sciurus niger rufiventer), a major objective being to determine, if possible, the effect of this species on forest reproduction. This investigation was a part of the program of a junior instructorship which continued through the following spring under the School of Forestry and Conservation, University of Michigan. I am grateful to Dean S. T. Dana and Alvin G. Whitney for arranging the financial assistance that made possible this year of study and field work and to Professors Whitney, H. M. Wight and L. R. Dice for advice and suggestions on this project. Two studies on caching and recovery of nuts to determine the percentage and method of removal from hiding places, were made in Forest Hills Cemetery in Ann Arbor. The squirrels were accus-