Sloth at Zoo Atlanta

A couple of famous pandas have been in the news recently over some troubles the two are having in the baby department.

In May, it was reported that the National Zoo had chosen to try artificial insemination with its popular female panda, Mei Xiang, who hasn't given birth to a cub since 2005. Just a few weeks later, there was even talk of possibly finding her a replacement mate!

Of course, it's a little hard for a zoo panda to get out and meet someone new. Plus, they can't just date whoever they think is cute.

When it comes to animal mating, zoos employ professional matchmakers who painstakingly organize breeding for many other zoo animals. They're called studbook keepers — and Vetstreet decided to chat with three of them to find out what it's really like to play critter matchmaker.

Two-toed Sloths: Slow But Steady Studbook Keeping

Animal keeper Lynn Yakubinis at Zoo Atlanta is the keeper of studbooks for two species of two-toed sloths, which have one problem in common with pandas: It's hard to decipher the sex of a sloth just by looking at it.

Yakubinis can make a match that looks great on paper — but when the animal arrives at its new zoo home, it sometimes turns out that "he" is really a "she."

But that isn't the only complication in connecting the right sloths. When dealing with two-toed sloths, there are two different species that look almost the same. And only a DNA test can tell for sure. "I've had to switch animals back and forth because they were in the wrong studbook!" Yakubinis says.

And even if all the animals are categorized correctly, Yakubinis needs patience to see results — after all, they're sloths.

The gestation time for Hoffman's sloths is 365 days, for example, so once you factor in moving the animals to their new habitat and then letting them get acquainted before mating, this is what Yakubinis considers a lightning-fast success story: "I sent one to Lincoln Park Zoo, and within two years, they had a baby."

There's suspense, too, because these animals share something else with those higher-profile pandas: It's hard to tell that sloths are pregnant, so you don't know for sure until the baby pops out. And Yakubinis might not even get to see this happen where she works because the male who's genetically best suited for the female at her zoo is also a good match for females living at other zoos.

"I have to do what's best for the population, not just for our zoo," she says. "It's like a big puzzle, and I have to do best by all the sloths, not just the ones I have."

Southern Ground Hornbills: It's a Family Affair

Roger Sweeney, assistant director of the Virginia Zoo in Norfolk, is the studbook keeper for four species of birds: the Andean condor, the fairy bluebird and the northern and southern ground hornbills. 

For Sweeney, birds often present different matchmaking challenges compared to mammals — in some cases, he may even be a bit envious of the slow timeline for breeding sloths.

"The easiest thing to manage as a studbook keeper is something that lives a long time, breeds slowly and lives in pairs," he says. Birds, however, tend to have a short lifespan, which also means a shorter reproduction period. Many feathered species also have complicated non-monogamous mating systems, so you need to keep more than just two birds to get one pair to successfully breed.

That said, Sweeney does manage one species with an interesting trait that's more common to mammals: Southern ground hornbills live in extended family units, and juveniles actually help to rear the chicks.

His analysis of their studbook data shows that birds who are raised independent of family groups are less likely to breed successfully as adults. "Compared to other birds that stay with parents for short periods of time," he says, "these birds have a lot more active social learning."

In other words, simply making good genetic matches isn't enough — Sweeney has to approach his job with an eye toward animal behavior as well. 

According to Sweeney, a bird with valuable genes who maybe hasn't been raised right can sometimes be carefully paired with a mate it can learn from — and prosper.

Thanks to his work, Sweeney has also changed the level of care that these birds receive at other zoos, which now also keep the birds in family groups.

Clouded leopard

Clouded Leopards: Love Is Dangerous

Studbook keepers sometimes find that individual animals aren't terribly cooperative.

Norah Fletchall is vice president of conservation for the Indianapolis Zoo, as well as a member of the committee that's responsible for the oversight of all Association of Zoos and Aquariums studbook keepers, from Partula snails to elephants.

For years, Fletchall was the studbook keeper for clouded leopards, and she had to deal with a problem that she delicately calls "mate incompatibility." Translation: Sometimes you introduce a pair and they try to kill each other.

"We don't want to put these animals' lives at risk, so people were hesitant to put them together," she says. And this is obviously a problem if you want to produce babies.

Little is known about the behavior of these cats in the wild, although it is believed that they come together only to mate. Since this wasn't working in captivity, Fletchall says, the idea eventually arose to introduce them as youngsters and raise them together.

A studbook keeper's job is to make sure that the genetics of a population stay diverse, avoiding over-breeding in some animals and under-breeding in others. So while these arranged marriages have been helpful, they've also introduced complications.

"What this means is that when you pair them, you pair them for life," Fletchall says. "If a male's line isn't well represented, and he's produced six litters with the same female, it's a dilemma."

Much like Sweeney, the clouded leopard studbook keeper has to consider behavior as well as genetics. So if adult clouded leopard pairs need to be rearranged, careful attention needs to be paid to age and size — but also individual personality.

The job of a studbook keeper is obviously rewarding, especially since hundreds of zoo people do it on top of their regular gigs. "It's a great way to get a broader look at things and contribute to conservation," Fletchall says. She even calls it "fun," although managing a huge database is the kind of fun that may not necessarily suit everyone. 

"You have to like to dig into detail," she says. "If you like things to be organized, being a studbook keeper is a lot of fun. I had records going back to 1890. You have a whole history in front of you all of the time."


Linda Lombardi is a former zookeeper, college professor and the author of Animals Behaving Badly, a book that grew from her blog of the same name.