Applying clinically proven human techniques for contraception and fertility to endangered species and zoo animals: a review.

Reversible contraception that does not alter natural behavior is a critical need for managing zoo populations. In addition to reversible contraception, other fertility techniques perfected in humans may be useful, such as in vitro fertilization (IVF) or oocyte and embryo banking for endangered species like amphibians and Mexican wolves (Canis lupus baileyi). Furthermore, the genetics of human fertility can give a better understanding of fertility in more exotic species. Collaborations were established to apply human fertility techniques to the captive population. Reversible vasectomy might be one solution for reversible contraception that does not alter behavior. Reversible approaches to vasectomy, avoiding secondary epididymal disruption, were attempted in South American bush dogs (Speothos venaticus), chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), Przewalski's horse (Equus przewalski poliakov), and Sika deer (Cervus nippon) in a variety of zoos around the world. These techniques were first perfected in > 4,000 humans before attempting them in zoo animals. In vitro fertilization with gestational surrogacy was used to attempt to break the vicious cycle of hand rearing of purebred orangutans, and egg and ovary vitrification in humans have led to successful gamete banking for Mexican wolves and disappearing amphibians. The study of the human Y chromosome has even explained a mechanism of extinction related to global climate change. The best results with vasectomy reversal (normal sperm counts, pregnancy, and live offspring) were obtained when the original vasectomy was performed "open-ended," so as to avoid pressure-induced epididymal disruption. The attempt at gestational surrogacy for orangutans failed because of severe male infertility and the lack of success with human ovarian hyperstimulation protocols. Vitrification of oocytes is already being employed for the Amphibian Ark Project and for Mexican wolves. Vasectomy can be a reversible contraception option in zoo animals, even in endangered species. Ongoing use of gamete and embryo freezing may salvage vanishing species.

Preliminary tests of a new reversible male contraceptive in bush dog, Speothos venaticus: open-ended vasectomy and microscopic reversal.

Open-ended vasectomies were performed on four male bush dogs (Speothos venaticus), with three having microscopic reversal surgery (vasovasostomy) between 10 and 20 mo post-vasectomy. The key to ease of reversal is leaving the distal (testicular) end open to allow leakage, resulting in a pressure-relieving granuloma. The proximal (abdominal) end is cauterized, providing an effective seal. This technique prevents the buildup of pressure in the epididymis, therefore limiting damage to the male's reproductive capacity. Described here are detailed procedures for both surgeries. One of the three males that underwent vasovasostomy has successfully impregnated his female partner. This study demonstrates that these techniques can be successfully applied to animals. With the two remaining pairs, none of the four individuals were proven breeders prior to the study, so it is not possible to eliminate the possibility of previously existing infertility. This technique may have limited application for carnivores, because vasectomy does not prevent potential adverse effects to females from prolonged, cyclic exposure to endogenous progesterone. In other taxonomic groups (e.g., primates, ungulates, marsupials, and rodents) in which multimale groupings are common, this reversible male sterilization technique could provide managers with the ability to control which males reproduce without eliminating their future reproductive capacity or social interaction.