Accuracy of Sex and Age Ratio Counts of White-Tailed Deer

Abstract

Field counts of white-tailed deer (Odocoileus virginianus) to determine fawn production, adult sex ratio, and population size assume equal observability of all individuals. Similar data from Virginia and Texas showed that there was rarely a period during summer or fall in which each sex and age class was equally observable. Fawns were always less observable than does during July, August, and September, the only period when they were easily differentiated from older deer. Bucks and does were usually seen at the same rate in August and November. Lincoln Index estimates were most accurate in November when all sex and age classes were most nearly equal in observability. Unequal observability was believed caused by differences in feeding and bedding time, not by group size or use of cover. J. WILDL. MANAGE. 41(4):709-714 Field counts of white-tailed deer are easily made in many areas, but the potential usefulness of such counts to estimate fawn production, adult sex ratio, and population size has not been demonstrated because of several apparent biases, foremost among which is deer behavior. This paper reports on a 3-year effort to quantify monthly changes in the observability of bucks, does, and fawns in an 826-ha deer-proof enclosure in Virginia and a similar effort conducted for 2 years in Texas. We thank personnel of the Radford Army Ammunition Plant, the Virginia Cooperative Wildlife Research Unit, and the Rob and Bessie Welder Wildlife Foundation for their cooperation and assistance. Thanks are also due E. L. Boeker, V. E. Scott, and C. P. Stone for reviewing the manuscript.