Cumulative Effect of Winter on Acorn Yield and Deer Body Weight

Abstract

We examined the effects of cumulative winter climate on acorn yield and body weight of immature white-tailed deer (Odocoileus virginianus) the following autumn, and spring population density of deer on Land Between the Lakes (LBL), Tennessee. Body weights of male and female fawns and yearlings were positively correlated with acorn yield the previous autumn and inversely correlated with estimated spring population density of deer. Acorn yield was positively related, and spring population density of deer inversely related, with the cumulative number of days with >0.25 cm of precipitation during the previous 3 and 4 winters. Acorn yield and associated body weights were not related to total amount of precipitation, presumably because of the topography of the study area. Cumulative effects of winter climate should be considered in deer population models. J. WILDL. MANAGE. 53(2):292-295 Severe winter weather can adversely affect ungulate fetal development and weight and potential survival of young. Most studies on effects of winter weather on cervid population dynamics have been at northern latitudes (45-50*) with corresponding low mean temperatures and significant accumulation of snow (Verme 1963, Peterson et al. 1982, Picton 1984). Recently, Mech et al. (1987) showed that snow accumulation had a strong cumulative effect on fawn: doe ratios of white-tailed deer and twinning rates and cow: calf ratios of moose (Alces alces). Our objectives were to determine if observed variation in body weights of immature white-tailed deer from a mid-southern latitude was related to winter climate and if there were cumulative effects of relatively moderate climate. T. Davin assisted with computer analyses. Computer time was provided by Southern Illinois University at Carbondale, Computing Affairs. R. A. Brandon, L. P. Hansen, H. A. Jacobson, and G. H. Waring provided helpful comments on the manuscript. Support for this study was provided by Land Between the Lakes, Tennessee Valley Authority, with additional funding from the National Rifle Association. STUDY AREA AND METHODS The study area was LBL, a 69,636-ha peninsula between Barkley and Kentucky lakes in western Kentucky and Tennessee. The area represents the midwest oak (Quercus spp.)-hickory (Carya spp.) forest region (Braun 1964) and consists of rolling uplands with steep hillsides 120170 m above sea level. Forest cover was approximately 90% dominated by oak and hickory. Vegetation in forest openings was dominated by lespedezas (Lespedeza spp.), Kentucky 31 fescue (Festuca elatior), white clover (Trifolium repens), grasses, and sedges. Deer body weight, acorn yield, and climate variables from the Tennessee portion (22,980 ha) of LBL (36830'N, 88000'W) were used because of the extent of available data from LBL records. Dressed weights of fawns and yearlings taken by hunters from October through December 1974-86 were recorded to the nearest 0.4 kg. Only fawns and yearlings were analyzed. Changes in cervid weight and growth are most evident at these ages (Halls 1978, Clutton-Brock et al. 1982) and reproductive activity, with the possible exception of yearling females, is not expected to affect body weight. Winter (Dec, Jan, and Feb) climatic data were recorded daily at the LBL Empire Farm Station (Golden Pond, Ky.). We analyzed the following variables that affect energy expenditure and nutritional plane of deer: mean minimum temperature in January, mean minimum temperature during the 3-month winter period, total precipitation in January, total precipitation during winter, and number of winter days with precipitation >0.25