Hormone monitoring of wildlife species: An important tool for studying reproduction and aiding breeding management

Brown, J.L.

Smithsonian Conservation Biology Institute, Center for Species Survival, Front Royal, Virginia 22630, USA, email: brownjan@si.edu

As more species reach vulnerable or endangered status, zoos are increasingly being tasked with sustaining genetically healthy populations in case of catastrophic extinctions. Unfortunately, many captive populations are not self-sustaining. It is now clear that the ability to track reproductive activity via hormones is key to developing successful ex situ breeding programs, through both natural and assisted reproductive means. What we have observed is a diversity of reproductive mechanisms used among the various taxa, even within closely related species. For example, among the Felidae, females of all species are induced ovulators, but in some species, females also exhibit spontaneous ovulations, and this can vary between individuals within a species. There are marked species differences in the impact of season on reproductive function, with some being exquisitely sensitive to photoperiod (e.g., Pallas’ cat), some moderately affected (tiger, clouded leopard, snow leopard), and others that are not influenced at all (e.g., ocelot, tigrina, margay, lion, leopard, fishing cat). One of the biggest challenges in ex situ breeding management is overcoming problems associated with highly variable ovarian responses to ovulation induction therapies used with assisted reproductive procedures, like artificial insemination (AI). Success is relatively high in the cheetah and ocelot, but few pregnancies have resulted after AI in clouded leopard, fishing cat and tiger. Among Perrisodactyla, there is a wide range in cycle lengths, including the finding that some species exhibit cycles of differing lengths (observed in white rhino and Malayan tapir). Presented are examples of how hormone monitoring has been used to study reproduction and enhance captive management efforts of diverse species. Many of these findings have been incorporated into husbandry manuals for specific species. Important endocrine findings related to animal management include: 1) learning that cheetah females experience reproductive suppression if housed together; 2) finding that reproduction in the seasonal Pallas’ cat is negatively affected by altered photoperiod (e.g., a zoo’s festival of lights); 3) the discovery of ovarian acyclicity in elephants and its relationship to socio-environmental factors; and 4) reinforcing how reproductive monitoring can aid breeding introductions of stress-susceptible species – canids, felids, many ungulates, even some primates. Given the relative ease of sample collection for most species (i.e., feces or urine) and critical need to increase birth rates within captive populations, it is imperative to establish hormone monitoring programs to aid basic research and applied management efforts.