Red Squirrel Responses to Spruce Cone Failure in Interior Alaska

Abstract

Observations were made on a red squirrel (Tamiasciurus hudsonicus) population in mature white spruce (Picea glauca) forest near Fairbanks, Alaska, during 2 years of spruce cone crop failure (July, 1964, to April, 1966). An adequate supply of old spruce cones, cached in previous years, was available during the first winter. A 67-percent drop in numbers of the squirrel population followed the second crop failure with the remaining squirrels utilizing spruce buds as their primary food during the winter. Stomach analyses revealed spruce seed, when available, as the major constituent in the diet. In its absence, utilization of mushrooms in summer and spruce buds in winter is heavy. Feeding trials conducted with captive red squirrels in March, 1965, and April, 1966, showed that about 194 old spruce cones per day were necessary to sustain a squirrel, approximately 35 percent more than for cones from the current year's crop. Three squirrels survived for 8 days on a diet of only white spruce buds. Excavation of middens revealed up to 8,500 old, cached cones per midden, despite a crop failure. Squirrels may cut and cache 12,000 to 16,000 cones, the excess accruing annually, eventually creating a supply sufficient to maintain the squirrels through a winter following a cone crop failure. This paper presents some aspects of red squirrel ecology during two consecutive years of cone crop failure in a mature white spruce forest in interior Alaska. The work was part of a study aimed at determining the ecological relationships of red squirrels to the production and supply of white spruce seed in interior Alaska. Because red squirrels utilize large quantities of white 1 Financed by the U. S. Forest Service's Northern Forest Experiment Station (Contract No. 12-11010-1650) and the Alaska Cooperative Wildlife Research Unit. 2 Present address: Department of Zoology, Canterbury University, Christchurch, New Zealand. s so e aspects of red spruce seed as the major constituent of their diet during years of normal cone production (Brink 1964), this study was oriented to determine food habits in the absence of a fresh supply of cones. One phase deals with observations of natural conditions on a study area within a mature white spruce forest. The second phase consists of a series of feeding trials conducted with captive red squirrels. The feeding trials were set up in such a way that the data would be directly comparable to those obtained by Brink and Dean (1966). Of the many persons who aided in the study, special thanks go to Dr. Frederick This content downloaded from 157.55.39.208 on Fri, 14 Oct 2016 04:09:41 UTC All use subject to http://about.jstor.org/terms 306 Journal of Wildlife Management, Vol. 32, No. 2, April 1968 C. Dean, Head, Department of Wildlife Management, University of Alaska; Dr. David R. Klein, Leader, Alaska Cooperative Wildlife Research Unit; Samuel J. Harbo, biometrician, Department of Wildlife Management, University of Alaska; and Robert A. Gregory of the Northern Forest Experiment Station at College, Alaska.