URBANA, Ill. (U.S.A.) — Zoos and private collections teach, inspire, and connect people to animals they may never encounter in the wild. And, in some cases, those animals represent valuable ‘assurance populations’ — essentially, backups that could be used to revive critically endangered populations in their native ranges. But new research from the University of Illinois Urbana-Champaign and Morfeld Research & Conservation shows American giraffe collections have been hybridized across species, sharply reducing their conservation value.
“Captive breeding programs in zoos would be better off restarting with fresh stocks from the wild, if they want to maintain assurance stocks for the purposes of conservation,” said senior study author Alfred Roca, professor in the Department of Animal Sciences, part of the College of Agricultural, Consumer and Environmental Sciences at Illinois.
Wild giraffes can’t afford to lose their backups. With a population of approximately 97,500 across 21 African countries, the animals have long been listed as vulnerable on the International Union for Conservation of Nature’s Red List. For conservation to work, though, there must be a basic understanding of which species are where, and how they interact with other populations and their environment. These fundamental questions help conservation biologists manage the unique needs of the animals they protect.
For years, all giraffes were thought to be part of a single species, with nine subspecies scattered across the African continent. However, recent advancements in DNA sequencing indicate that giraffes actually fall into four distinct species that rarely intermingle, much less interbreed. Earlier this year, the IUCN formally recognized all four species as vulnerable, with several populations categorized as critically endangered.
Why does this matter for captive collections? As genetic repositories for wild populations, animals in human care should represent what’s in the wild. But, after analyzing the DNA of 52 giraffes across American facilities, including private ranches and zoos, Roca and his collaborators found the opposite: these animals have become a genetic mish-mash, reflecting decades of interbreeding and hybridization.
“We compared the DNA sequences of giraffes from North American collections to 63 wild individuals across all four species and were able to see how strongly their genetics aligned with different species in the wild,” said Wesley Au, the study’s first author and doctoral researcher in the informatics program at U. of I. “Only eight giraffes got close to representing a single species — reaching about a 90% match — but the rest were a mix of two and sometimes three species.”
Chris Fields, study co-author and lead of the HPCBio core in Illinois’ Roy J. Carver Biotechnology Center, added, “This study demonstrates how to perform conservation studies through genomics, by comparing genome data from the giraffes to reference genomes from wild species.”
The team determined that a handful of individuals may have originated from a wild reticulated giraffe that itself was a rare natural hybrid. According to the researchers, the others may have resulted from a 2004 Association of Zoos and Aquariums policy to manage most giraffe breeding as a single ‘generic’ unit, rather than maintaining separate breeding programs for individual subspecies, as the AZA had done previously.
“The AZA decision acknowledged that hybridization was already extensive within its giraffe population,” Roca said. “Additionally, I'm not sure it was obvious in 2004 that the animals were from such disparate genetic stocks. Those studies came later, so it's not surprising.”
Study co-author Kari Morfeld says captive breeding programs often prioritize animal demeanor.
“A lot of times, decisions to breed animals are based on, ‘She's a nice female, he's a nice male. Let's put them together for breeding.’ The genetics aren’t usually considered in making breeding decisions for giraffes, but they should be. We have a responsibility to consider genetics, not only demeanor or physical characteristics, to do better for giraffe conservation,” said Morfeld, reproductive physiologist and owner of Morfeld Research & Conservation.
The researchers recommend phasing out hybridized animals from the captive breeding program. These animals certainly have inherent value, especially as ambassadors for giraffes, and some could potentially serve as surrogates for implanted embryos representing wild genetics. Additionally, more animals could be screened to learn whether better genetic matches to wild populations already exist within the American giraffe collection.
Finally, the authors say giraffe conservation plans can’t hinge entirely on zoos and ranches — major investments are needed to restore wild populations in Africa, some of which have dwindled precipitously close to local extinction.
Morfeld acknowledges that starting the breeding program from scratch with wild genetics would be a logistical challenge.
“Physically moving these huge animals between continents would be difficult. So, a better way, in my opinion, is to develop reproductive technologies where you can move semen or embryos and proceed with artificial insemination, IVF, and embryo transfer. We do this all the time in livestock and other species. There's no reason this can't be applied to giraffes.
“And there are a lot of things to consider beyond moving genetics,” Morfeld added. “It really comes down to establishing trusting relationships with African governments, conservation organizations, and scientists. It's one thing to conduct an artificial insemination, but you really have to ask the question of how all stakeholders will benefit.”
The study, “Genomic assessment of giraffes in North American collections highlights conservation challenges,” is published in the Journal of Heredity [DOI: 10.1093/jhered/esaf089]. Authors include Wesley Au, Kari Morfeld, Christopher Fields, Yasuko Ishida, and Alfred Roca.
Research in the College of ACES is made possible in part by Hatch funding from USDA’s National Institute of Food and Agriculture. This study was also supported by Morfeld Research & Conservation, LLC, Daniel Houck II, and Missy Howell.
Roca is also affiliated with the Carl R. Woese Institute for Genomic Biology, the School of Information Sciences, and the Illinois Natural History Survey, part of the Prairie Research Institute at U. of I.