Abstract

Facing a major reproductive success in human care, it seems increasingly necessary to better understand the physiology of reproduction in Otariids and to develop reliable techniques of birth control. Physical separation, permanent castration, reversible and immunological contraception are all means of control used by zoos and marine facilities to master the reproduction of their animals. The ultimate goal is to ensure optimal genetic diversity, reduce overcrowding and the risk of intraspecific conflicts that may arise. Currently, scientific information on the various methods and consequences of contraceptive methods used among sea lions are very limited in the literature.^1-9

Deslorelin and Goserelin are both GnRH agonists that suppress the production of sex hormones (testosterone and estrogen) by feedback mechanisms, with an effect similar to ovariectomy or castration but having the advantage of reversal upon expiration of the hormonal content of the implant. Because of their effect on the suppression of testosterone, these agonists have been used in males both for temporary castration and aggression control. The latest effect is important for pinnipeds presentations in zoos, marine parks and aquariums, where the highest public attendance coincide most of the time with the summer season and peak reproductive season of the animals.

A preliminary study with both types of implants was performed over several years, with different protocols and with relative flaws and successes, with males of two different facilities, comprising mixed groups of Patagonian sea lions (Otaria byronia), California sea lions (Zalophus californianus) and Harbour seals (Phoca vitulina). Goserelin had been chosen as part of the trials for its biodegradability and short acting (3M) effect, to purpose being to identify, for some animals, if one could postpone "heat" in males and reproduction until the end of the public season. Males were followed by regular blood samplings for testosterone controls and implants booster adjusted based on these results. In some cases females became pregnant though no typical reproduction behaviour were shown by the males during the respective summer. It was not possible in this study to identify if it was through the presence of residual sperm storage at the time of the first implant, an incorrect estimation of the testosterone level through available laboratory tests, or a later impregnation of the females. Some males also had a return of their typical "heat" behaviour six months past first implant, so in the middle of the winter in Europe, when using Deslorelin or Goserelin.

This has led to the development of a thorough on-line questionnaire, aimed at veterinarians and institutions holding these species, in order to review the different techniques used nowadays and their relative success and/or failures.

During this presentation, current knowledge on contraceptive methods in pinnipeds will be overviewed and the questionnaire will be explained. The information collected herewith and their analysis will permit, in the near future, the realization of a synthetic work on the control of reproduction knowledge in sea lions, but this can only happen if the information is made available.

* Presenting author

Literature Cited

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