DOSE DETERMINATION AND EFFICACY OF REMOTELY DELIVERED NORGESTOMET IMPLANTS ON CONTRACEPTION OF WHITE-TAILED DEER

Management of overabundant wildlife populations using contraceptives i s being considered with increasing frequency in many localities. A wid e array of effective contraceptives is needed to meet a variety of man agement objectives. Therefore, we evaluated the synthetic progestin no rgestomet for its efficacy and its minimum effective dose in free-rang ing white-tailed deer (Odocoileus virginianus). We evaluated two doses of norgestomet implants (14 and 42 mg) at a site in southern Connecti cut during 1992-1995. Four doses (14, 21, 28, 42 mg) of norgestomet im plants were tested at a site in northern Indiana during 1993-1996. The effectiveness of norgestomet implants in preventing pregnancy was sim ilar for the 42 mg (92%), 28 mg (100%), and 21 mg (100%) doses. There was a significant decline in efficacy using the 14 mg (48%) dose. It a ppears that 21 mg is approximately the lowest dose that consistently p revents reproduction in adult white-tailed deer of various sizes and a ges. Norgestomet implants show promise as a highly effective contracep tive agent that is safe to treated animals and secondary consumers and simple to deliver remotely. (C) 1997 Wiley-Liss, Inc.