For Association of Zoos and Aquariums (AZA)-accredited facilities, maintaining sustainable animal populations can feel like playing a game of chess. In order for animal populations to be sustainable, the animals must reproduce. But because of limited space and resources, and because of animal compatibility, health challenges and individual personalities when, where and, often, how that reproduction happens can require complex strategies, tactics and research.
To put it in human terms, that’s where the matchmakers and family planners of the accredited zoo and aquarium world come in. The AZA Population Management Center (PMC) is based in a small office building at Lincoln Park Zoo in Chicago, Ill., a few steps from the dwarf crocodiles and pygmy hippos that make their home in Regenstein African Journey. There, a team is hard at work conducting demographic and genetic analyses and making plans for breeding and transfer of Species Survival Plan® (SSP) program animals in order to meet management goals.
“The goal of the SSPs and of the PMC is to keep those populations as healthy as we can for as long as we can,” said Sarah Long, director of the PMC. “So [determining] the right numbers of births happening, the right genetic pairs—that’s the infrastructure for how we do the day-to-day management for these populations.”
Long and the team at PMC rely on research and technological advances to ensure that SSP animals continue to reproduce in a genetically healthy manner well into the future. They rely, in part, on computer programs that analyze studbook databases containing information on all of the animals and their genetic relationships. But while the computer can highlight matches that make sense on paper, it takes human insights to determine if the match makes sense from a personality standpoint and logistics standpoint—i.e. is it feasible to find animals at the same facility, or will a transfer be necessary? When those animals are put together, will they get along with one another?
Every one to three years, the PMC team makes recommendations on what different SSP teams need to do, in terms of genetics and demographics, to keep their population on track. That could mean breeding, preventing breeding, selecting mates or other recommendations.
Long said that a successful pairing depends on collaboration. While Long may be the one to propose a good genetic pair, SSP coordinators and others who are more familiar with the particular animals are able to share their history, age, behavior, reproductive research and other information, to help shape breeding and transfer plans. “It really benefits us to have a room full of people who remember bits and pieces of this and bring it to the table,” said Long.
If the PMC staff act as matchmakers, then Dr. Linda Penfold serves as the couples’ counselor—among her many other responsibilities, such as performing fertility checks, semen collection, contraception and breeding planning and more. Penfold is the director of South-East Zoo Alliance for Reproduction & Conservation, a non-profit based in Yulee, Fla., that works with 12 AZA-accredited facilities, using science and research to help maintain sustainable populations and provide advice to many other others.
Penfold said that she and her staff often start the process of addressing reproductive challenges by examining things like social grouping. She said that while her 25 years’ experience in the industry is helpful, she also relies on the zoo and aquarium staff to educate her on particular animals and what their behavior in the wild is like. For example, if a zoo is having trouble getting a pair of lions to breed, its staff will seek out Penfold’s expertise. In one particular case, the male and female had been living together for years and just didn’t seem interested in taking their relationship to the next level.
“Our recommendation: we’ve got to stir things up a bit,” said Penfold. She instructed the staff to collect fecal samples from a male lion that the female had never met and put it around the area. That way, the male would think he had some competition, and the female would think there was another lion out there. “The staff did this and in a couple of weeks, the female came into roaring estrus, the male bred her and she produced lion cubs,” said Penfold. “And that’s as low-tech as you can get.”
Other pairings require more research and intervention. Take stingrays, for example. Penfold is currently conducting research to determine why a number of facilities are finding cystic ovaries that are ultimately leading to their death. After one of the facilities she works with approached her about the reproductive disease, Penfold realized that the majority of facilities she works with that have stingrays are also experiencing the same challenges with reproduction. Because she works with so many facilities, she’s been able to study a number of captive and free ranging rays to get a better understanding of what is going on. In the study, she learned that the treatment she’d thought would work and that veterinarians had been recommending—progesterone—wasn’t as effective as hoped.
Penfold suspects that the problem could have something to do with what is referred to as the “use it or lose it” phenomenon—animals that don’t breed at a young age struggle to reproduce later in life. It’s a problem that has been documented in many other animals, including elephants, hoofstock, rhinos and others. She said it is something she is continuing to study, along with other areas such as water quality and other environmental factors, to try and determine what is causing the problem across the stingray populations. “We still are investigating further treatment to see if we can figure out, first of all, how to treat it, and more importantly how to prevent it from happening in the first place.”
At the AZA Reproductive Management Center—formerly the AZA Wildlife Contraception Center—at the Saint Louis Zoo in Saint Louis, Mo., director Dr. Cheryl Asa oversees research on reproduction, reproductive challenges and contraception, and was recently honored with the 2015 AZA's Devra Kleiman Award for her scientific contributions to the field.
One of the areas that Asa and her colleagues have been focusing on is lifetime reproductive planning. They’ve seen the challenges that females across varied species face when they don’t reproduce until later in life (as in stingrays), so they’re working to address that, while also keeping population numbers at a level that makes sense with the physical space available to house them in zoos and aquariums. Asa said that one approach involves reproductive planning for each female, rather than simply taking a big-picture approach and planning around population numbers and needs. She said that approach may mean determining, early on, how many offspring staff hope for a female to contribute, and then allowing her to breed while she’s young and fertile, rather than years down the line, when her ability to reproduce declines.
Asa said there are also a number of things that zoos and aquariums can do, themselves, to improve population management, including endocrine monitoring. She said fecal samples will indicate if a female is ovulating and semen samples will provide insights into male fertility. “Endocrine monitoring, we believe, should now be looked at as business as usual and part of modern management of zoos,” said Asa.
For veterinary epidemiologist Dr. Pam Dennis, overall health is key when it comes to all aspects of a species, including reproduction. “If you have health issues as an individual, your likelihood of breeding declines. If you are unhealthy, your likelihood of sustaining pregnancy declines. If you are unhealthy, the likelihood of even having viable reproduction declines,” said Dennis, who works at Cleveland Metroparks Zoo in Cleveland, Ohio, and is a clinical assistant professor at the Department of Veterinary Preventive Medicine with The Ohio State University.
Dennis, who is the former chair of AZA’s Animal Health Committee, emphasizes that animal health underlies all aspects of zoo and aquarium life. And when it comes to population sustainability, it’s not just about counting babies. It’s about continuing the reproduction for generations to come. She shared an example of the challenges she has faced at Cleveland Metroparks Zoo, which has developed a reputation for its success with breeding koalas. Dennis said she was looking through koala paperwork and saw that one koala, in particular, had been reproducing successfully, but then problems were later arising. Of five joeys, only one—the only female—survived to adulthood. The males all died at around 7 months of age.
Dennis began researching what the problem could have been, and found that the koalas, before they died, hadn’t been growing at the same rate as the rest of the population. She questioned if anything could be added to the mom’s diet—the only food koalas eat is eucalyptus—to help the babies grow. She learned that in Australia, koala caretakers will sometimes give a milk replacement supplement to geriatric koalas and orphaned koalas. So, she gave supplements of that to the mom and, over the years, her next two joeys survived and reached sexual maturity. While Dennis said she can’t scientifically prove that the supplements solved the problem, it seems to have made a difference.
The bottom line, said Dennis, is in order to have animals that reproduce offspring that also go on to reproduce into the future, overall health of the species is vital. She said that in zoos and aquariums, it is common to look at animals that aren’t breeding and question the mate choice, timing or other scenarios. The reality, she said, could be more straightforward.
“We aren’t going to have sustainable populations if the animals are not healthy,” said Dennis.
Kate Silver is a writer based in Chicago, Ill.