Abstract
Due to the relatively smaller populations of pinnipeds maintained in zoos and aquaria compared to other non-domestic species, a greater emphasis has been placed upon the development of successful captive reproduction programs, rather than contraceptive techniques, for these species. However, effective population management often requires selective breeding, and the development of reversible contraceptive techniques provides a management tool to achieve these objectives. To date, there have been limited contraceptive attempts in pinnipeds.1,3,6,7
Most pinnipeds, including the Northern fur seal (Callorhinus ursinus), have a highly seasonal reproductive pattern. Contraception can therefore be achieved through limited intervention during the breeding season. Strategic intermittent administration also minimizes the potential for adverse effects from contraceptive use.3,7
The New York Aquarium maintains a colony of Northern fur seals that included six animals (one 11-year-old breeding male, two immature males, and three 13- or 14-year-old females) at the initiation of the study. Two females had conceived eight times in the preceding 6 years. Contraception was achieved by the IM administration of leuprolide acetate for depot suspension (Lupron Depot 3.75 mg, TAP Pharmaceuticals, Inc., Lake Forest, IL, USA). Utilizing a trained presentation behavior, 18.75 mg (five vials reconstituted with 3 ml diluent) was administered monthly for 6 months through the breeding season (28 April to 29 September 2003 and 7 May through 1 October 2004). Male Northern fur seals undergo marked weight changes during the breeding cycle, and throughout the treatment interval his weight ranged from an early high of 260 kg to a terminal low of 130 kg. There were no births in 2004, and no evidence of pregnancy to date in 2005.
Leuprolide acetate has been used successfully for male contraception in Atlantic bottlenose dolphins (Tursiosp truncatus),2,3,7 California sea lions (Zalophus californianus),3,7 and harbor seals (Phoca vitulina),3,7 and to control aggression or other male-associated behaviors among all male groups of California sea otters (Enhydra lutris)4 or California sea lions.5 Adverse injection site reactions observed in California sea lions in another study5 did not occur in this Northern fur seal. The seasonal use of leuprolide acetate for male contraception in this Northern fur seal colony proved to be an effective and practical contraceptive technique and may have application to other colonial, seasonally reproductive, pinniped species.
Acknowledgments
We thank the keepers at the New York Aquarium for their expert assistance, especially JoAnne Basinger, Paul Moylett and Gina Fisher. The leuprolide acetate used in this study was provided by Veterinary Services, Brookfield Zoo, Chicago, IL, USA.
Literature Cited
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