Seasonal Changes in Heart Rates, Activity, Metabolism, and Forage Intake of White-Tailed Deer

Abstract

White-tailed deer (Odocoileus virginianus) exhibited seasonal rhythms in heart rates, activities, and metabolism, with the lowest ecological metabolism occurring in the winter and highest in the summer. This rhythm is an adaptation for energy conservation; resource needs are lower when range resources are reduced. A series of equations is used to estimate ecological metabolism and forage consumption from measured heart rates and activity patterns throughout the year. The highest energy expenditure (about 4 times baseline metabolism) is estimated for a female with 2 fawns during the lactation period, and the lowest (about 1.5 times baseline metabolism) for deer in midwinter. As metabolism rises in March and April, the intake of dormant forage should also rise until more digestible spring growth is available. The timing of the arrival of spring seems to be an important factor in population dynamics, with its effect being most pronounced 2 years later when the fawns should become members of the breeding population. J. WILDL. MANAGE. 42(4):715-738 The free-ranging animal presents several acute problems for the physiological ecologist interested in quantifying the animal's of living over the annual cycle. Knowledge of this cost is fundamental to an understanding of productivity, for an animal can be productive only if the range supplies nutrients in excess of the level necessary for maintenance. There is ample evidence for this in the literature; it is well known that deer on overstocked range are smaller in size, have fewer fawns, and have smaller antlers than those on range that is properly stocked. Difficulties in the direct measurement of the metabolism of free-ranging animals are sufficiently great to compel one to seek alternate methods of estimation. This paper presents a method for predicting ecological metabolism (Moen 1973) and forage intake of white-tailed deer based on equations derived from several years of physiological telemetry measurements at the Wildlife Ecology Laboratory, Cornell University, and additional data from the literature. Funds for this research have been provided by the New York State Department f Environmental Conservation through Pittman-Robertson Project W-124-R and the N.Y. State College of Agriculture and Life Sciences, Cornell University. Special thanks are due Anne Hiller and Barbara Buxton for their part in the training and measurements on experimental deer, Joanne Paul for summarizing data, and Elyse Egan for verifying each of the equatio s. I wish to recognize Helenette Silv r for her pioneering work on the metabolism of white-tailed deer in the 1950's which served as an important foundation for my research in the 60's and 70's.