Five female California sea lions (Zalophus californianus), ranging in age from four to twelve years, were contracepted. Three sea lions were multiparous and delivered healthy pups in June or July of 1991. One primiparous sea lion had given birth in 1987 and the fifth animal (four year old) was nulliparous. Each sea lion received 200 mg medroxyprogesterone acetate' three times at monthly intervals. Injections were performed via dart', using 6 cm needles into the musculature of either the shoulder or rear limb. Initial injection was performed ten to twelve days postpartum (18 June to 2 July) in the three sea lions giving birth in 1991 or on the second or sixteenth of July in the remaining two sea lions. Each sea lion subsequently received two additional injections at three to four week intervals.

The primiparous sea lion died 9 months after initiation of the study of unrelated causes; she was not pregnant and no mammary or uterine lesions were noted. None of the remaining sea lions gave birth in 1992. A series of three injections was repeated at monthly intervals beginning on 24 June 1992 and the results of the second year are not yet known.

The medroxyprogesterone acetate dose used for sea lions was extrapolated from a preliminary contraception study conducted in female grey seals (Halichoerus grypus).¹ Potential adverse effects of exogenous progestogen administration in carnivores include diabetes, cystic endometrial hyperplasia, pyometra and mammary gland neoplasia.² At the dose used, adverse physiological effects of hormonal treatment were not observed and successful contraception was achieved.

Products Mentioned

^aDepo-Provera, The Upjohn Company, Kalamazoo, Michigan 49001, USA
^bTelinject USA, Inc., Saugus, California 91350, USA

Acknowledgements

The authors thank the Mammalogy Department, especially Claudia Wilson and Marge Gavlik for assistance in conducting this study.

References

1.  Seely, A.J. and R. Keith. 1991. The effect of depo-provera on reproduction in the grey seal (Halichoerus grypus). Proc. Am. Assoc. of Zoo Vet. Pp 304-310.

2.  Concannon, P.W. and V. N. Meyers-Wallen. 1991. Current and proposed methods for contraception and termination of pregnancy in dogs and cats. J. Am. Vet. Med. Assoc. 198(7):1214-1225.