Gestation Period, Breeding and Fawning Behavior of Columbian Black-Tailed Deer

The determination of gestation period and observation of breeding and fawning behavior of animals in the wild are generally difficult; data concerning these fundamental aspects of deer biology are, therefore, often fragmentary and of a subjective nature. Much of our information concerning gestation period and behavior of deer has been obtained through observations made in zoological parks or other unnatural situations. Although these observations are of considerable value, bias may be introduced when these types of data are applied to wild animals. While engaged in the study of reproductive performance of Columbian black-tailed deer (Odocoileus hemionus columbianus) the writer was able, through the facuities of the Deer Project of the State of Washington Department of Game, to minimize both of the above difficulties by observation of a herd of semi-wild deer which could be penned during the observation period. Methods.—The herd utilized for this experiment consisted of 11 does and 1 three-year-old buck. Four of the does were mature (over 1.5 years old) and 7 were yearlings. The pens in which the experiment was conducted consisted of eight individual fenced enclosures, 84 by 15 feet, connected by a five-foot-wide alleyway running along one side of the pens. A scale house for weighing the deer, with a large window overlooking the pens, was situated in the center of the alleyway.