Metabolic and Endocrine Responses of White-Tailed Deer to Increasing Population Density

Abstract

Blood samples were collected in March each year, 1969-1977, and in Nov., 1974, 1975 and 1976 from white-tailed deer (O. virginianus) living in a 252-ha enclosure. The animals were provided ad lib supplemental food beginning in Jan., 1972, and the population was allowed to increase with no removals except by accident. The number of animals increased from 23 (0.09/ha) in March 1972 to 159 (0.63/ha) in March, 1977. Values for serum urea N, thyroxine, mean corpuscular Hb concentration and white blood cells were lower during years prior to supplemental feeding and values for hematocrit were higher. No consistent differences were detected in glucose, cortisol, mean corpuscular volume, red blood cells and Hb as a result of feeding or increasing population density. The only changes correlated with increasing population size were increasing numbers of white blood cells in fawns and adult does and decreasing red blood cell size in fawns. Serum cortisol, serum cortisol responses to ACTH stimulation and adrenal weights were not related to deer population density. Pregnant does had lower serum urea N, glucose and thyroxine concentrations than fawns or adult bucks. There was no evidence for a simple density-dependent elevation in adrenal corticosteroid secretory activity in healthy, well-fed white-tailed deer from a population with rapidly increasing numbers.