Managing reproduction is central to successful breeding programs. That probably first brings to mind the selection of genetically appropriate breeding partners, but equally important is preventing reproduction in those individuals not receiving a breeding recommendation in a given year. Limiting reproduction is important for a number of reasons. Because zoos don’t have unlimited space for every species in their care, not all females can be allowed to produce offspring every year. Another important benefit of contraception is that it allows family and social groups to be maintained, which supports animal well-being while avoiding inbreeding and allowing reproduction by recommended pairs.
The Association of Zoos and Aquariums recognized the potential role of contraception in breeding programs by approving formation of the Contraceptive Task Force in 1989. It was soon obvious that tailoring contraceptive recommendations for the broad range of species in zoos would require a longer-term commitment than a temporary task force. That resulted in formation of the AZA Contraception Advisory Group (CAG) in 1992. The advisors included reproductive physiologists, curators, and veterinarians who were interested in evaluating the possible methods and application of contraceptives in zoo populations.
Contraceptive use in zoos wasn’t completely new. Ulie Seal had shown that synthetic progestins could suppress reproduction in lions as early as 1976 (Seal et al. 1976). In that study he identified melengestrol acetate (MGA) as having the fewest side effects of the progestins tested and subsequently provided MGA in silastic implants to zoos free of charge. However, there were no central records of products used in zoos, which might include those designed for humans. Nor were there data on outcomes of contraceptive treatment. Thus, one of the first objectives of the CAG was to create such a database, an effort that began by mailing an annual survey to all AZA facilities.
That paper survey evolved into an electronic one and then to a website for direct online input of contraceptive data. The website represents a joint effort with our European Association of Zoos and Aquaria sister organization, the EAZA Reproductive Management Group (RMG), based at Chester Zoo in the United Kingdom. After the RMG (first called the European Group for Zoo Animal Contraception, EGZAC) was organized, we agreed to standardize and combine our respective databases to increase the amount of information available for analysis.
The Contraception Database now contains more than 50,000 records of contraceptive use by zoos around the world; over 41,000 of those records are from AZA facilities. The database, along with results from research and monitoring projects, informs the recommendations posted our webpages, which are on the Saint Louis Zoo website. The Zoo has hosted the AZA contraception program through its various incarnations and has funded much of its work.
As the contraception program continued to grow, AZA recognized its central role, along with the AZA Population Management Center (PMC), in its breeding programs. Soon after the PMC was established, the CAG was re-named the AZA Wildlife Contraception Center (WCC) in 2001. That step also fostered a closer and more formal working relationship between the two AZA centers. CAG members became the WCC Advisory Board that continued to meet annually to review program activities, as well as being available throughout the year to provide advice to the WCC and the AZA community.
The WCC continued conducting research and monitoring projects, updating contraceptive recommendations, and responding to questions and concerns about products and their application. Being an official AZA Center made it possible for the WCC to negotiate with companies to make more contraceptive products available to AZA member facilities, usually at a reduced price.
In 2015, the Wildlife Contraception Center was re-branded as the AZA Reproductive Management Center (RMC). This change reflected an expansion of focus from limiting reproduction to actively trying to promote it. It was well-recognized that many AZA populations were not breeding at levels necessary to sustain themselves for the future (Long et al, 2011), and in some cases this was due to lack of reproductive success rather than simply limited space.
Prior to the name change, the WCC had been made aware of increasing issues with poor reproductive success, and in fact, the WCC convened a workshop at the AZA Annual Conference in 2014 aimed at raising awareness about factors contributing to infertility and developing tools for practitioners to use to identify possible causes of poor reproductive success. The RMC also co-authored two important papers in 2014 that raised awareness of how certain breeding management practices could contribute to reduced fertility and increased reproductive pathology (Asa et al, 2014; Penfold et al, 2014).
From its inception, the CAG collaborated with veterinary pathologist Linda Munson who established the Contraceptive Health Surveillance Center to monitor the safety of contraceptive product use in wildlife. As the purview of the WCC expanded to include enhancing reproductive success as well as contraception, that program expanded to become the Reproductive Health Surveillance Program (RHSP), now run by Drs. Dalen Agnew and Anneke Moresco.
Part of the mandate to expand the RMC’s focus also included consideration of non-mammalian taxa, as mammals had been the main focus of the Center for decades. The RMC expanded its Advisory Board, adding individuals with expertise in avian, reptile/amphibian, and aquatic species, to help the RMC maintain awareness of emerging needs and challenges in these taxa. The RMC developed training opportunities to improve reproductive management in these taxa, including video tutorials on semen collection in lizard species and how to assess bird and reptile eggs for the presence of sperm. The RMC also organized a crane fertility workshop at the AZA meeting in Jacksonville that presented material on reproductive behavior and physiology of cranes, assisted reproduction, and animal handling techniques to improve reproductive success. RMC staff also liaised with representatives at professional meetings from the Marine and Freshwater Fish TAGs, as well as the Aquatic Invertebrate TAG, to discuss where the RMC might be of service.
More recently, the RMC has partnered with Meghan Martin from PDX Wildlife to expand the zoo community’s consideration of mate choice in improving reproductive success. Most animals exhibit some degree of selectivity when choosing mates in the wild, and it makes sense that they would in human care as well. However, providing opportunities for mate choice has not been explicitly considered in most breeding programs to date. The RMC recently published a paper on how zoos and aquariums might consider incorporating mate choice into population management (Martin-Wintle et al., 2019) and just this past summer (2021) piloted a virtual course for zoo personnel on increasing mate compatibility via mate choice to improve population sustainability.
In addition to these outreach activities, the RMC began to think about how we might better plan reproduction in managed populations such that fertility could be maintained by limiting exposure to contraception or long-periods without breeding. Decisions about when and how to limit a female’s reproduction have impacts on population size, demography, and genetics, and so the RMC has built a stronger relationship with the PMC and has identified ways for the two AZA Centers to collaborate and share data to amplify both Centers’ effectiveness. This collaboration helped the RMC to develop a new process called Reproductive Viability Analysis (RVA; Bauman et al., 2019) that helps to uncover what biological factors are associated with better reproductive success. For example, in fennec foxes, male and female age as well as reproductive and pair history are important drivers of reproductive success. RVAs have also been done for Mexican gray wolves, Asian small-clawed otters, and red river hogs.
The second initiative the RMC has pioneered is Lifetime Reproductive Planning (LRP). This is a computer-modeling exercise that allows us to understand what impact different breeding management strategies (e.g., breed all females once at sexual maturity and then allow them to have no further offspring, one future offspring, etc.) have on population genetics and population size. This technique allows us to incorporate the impacts of contraception on later fertility and can account for changes in breeding practices informed by RVA. Recently, the RMC demonstrated that when RVA results are included in these models, population viability for the long-term is better (Franklin et al., 2020). Eventually these models will be invaluable in guiding breeding efforts to maintain fertility and reproductive success while balancing demographic and genetic needs of managed populations.
The RMC continues its work in reproductive management via contraception, and has recently published analyses related to contraceptive safety, efficacy, and reversal (e.g., Drake et al., 2021; Guthrie et al., 2021; McDonald et al., 2020). Recently, we have updated our Reproductive Checklist to Assess Fertility tool in collaboration with the AZA Reproduction and Endocrinology Scientific Advisory Group and the EAZA Reproductive Management Group. We have also created a contraception “at-a-glance” resource that provides a quick overview of contraceptive methods for different taxa as well as a contraception decision-tree tool for making contraceptive decisions. These tools are freely downloadable from Saint Louis Zoo.
As the RMC embarks on its 21st year, we foresee continuing to expand our ability to help improve reproduction in animal populations that are struggling to breed. Further collaboration with the Reproduction and Endocrinology as well as Behavior SAGs and TAGs will be essential. Behavior has always been central to reproduction, and the RMC looks forward to expanding its offerings in terms of behavioral advice to promote successful breeding. The AZA Aquatic Collections Sustainability Committee is also bringing new programs online to foster and promote larval rearing programs for fish. The RMC looks forward to assisting with these programs as they develop and continues to have aquatic representation on our advisory board. The RMC will definitely continue to get its feet wet as we wade into the aquatic realm. Contraception will remain a cornerstone of our work. In the next year we plan to update our contraceptive recommendations based on new work by the Center and other scientists. With AZA members’ help, we are also tracking the availability and use of new contraceptive approaches as they emerge. The next 20 years will be busy but hopefully very (RE)productive.
Dr. David Powell is the director of the AZA Reproductive Management Center and the director of research at the Saint Louis Zoo.
Dr. Cheryl Asa is the chair of the Reproductive Management Center Advisory Board.
Asa, CS, Bauman, KL, Devery, S, Zordan, M, Camilo, GR, Boutelle, S & Moresco, A. 2014. Factors associated with uterine endometrial hyperplasia and pyometra in wild canids: implications for fertility. Zoo Biology 33:8-19.
Bauman, K, Sahrmann, J, Franklin, A, Asa, C, Agnew, M, Traylor-Holzer, K & Powell, DM. 2019. Reproductive viability analysis as a new tool in captive animal management. Zoo Biology 38:55-66.
Drake, GJ, Cowl, VB, Ashpole, I, Rowland, H, White, D, McDonald, M, Chantrey, J, Lopez, J & Feltrer-Rambaud, Y. 2021. The etonogestrel (Nexplanon®) and aglepristone (Alizin®) for population management of a colony of Rodrigues fruit bats Pteropus rodricensis. Journal of Zoo and Aquarium Research 9:239-246.
Franklin AD, Lacy RC, Bauman KL, Traylor-Holzer, K & Powell, DM. 2020. Incorporating a Reproductive Viability Analysis into a Population Viability Analysis for Ex Situ Population Planning using Vortex. Animal Conservation 24:386-400.
Guthrie, A, Strike, T, Patterson, S, Walker, C, Cowl, V, Franklin, AD & Powell, D. 2021. The past, present and future of hormonal contraceptive use in managed captive female tiger populations with a focus on the current use of deslorelin acetate. Zoo Biology 40:306-319.
Long, S, Dorsey, C & Boyle, P. (2011). Status of Association of Zoos and Aquariums cooperatively managed populations. WAZA Magazine, 12:15–18.
Martin-Wintle, MS, Wintle, NJP, Díez-León, M, Swaisgood, RR & Asa, CS. 2019. Improving sustainability of ex situ populations with mate choice. Zoo Biology 38:119-132.
McDonald, MM, Agnew, MK, Asa, CS & Powell, DM. 2020. Melengestrol Acetate contraceptive implant use in Colobus monkey (Colobus guereza): patterns through time and differences in reproductive potential and offspring survival. Zoo Biology 40:124-134.
Penfold, L, Powell, D, Traylor-Holzer, K & Asa, C. 2014. “Use it or lose it”: Characterization, implications, and mitigation of female infertility in captive wildlife. Zoo Biology 33:20-28.
Seal, US, Barton, R, Mather L, Olberding, K. Plotka, ED, & Gray, CW. 1976. Hormonal contraception in captive female lions (Panthera leo). Journal of Zoo Animal Medicine 7:12-20.