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Zoo matchmakers help animals do what should come naturally

Zoo matchmakers help animals do what should come naturally
Mitch O'Connell

Hollie Colahan's second-floor office at the Denver Zoo features a standard magnetic whiteboard. But its content is far from standard: This is the Magnetic Whiteboard of Lion Sex.

That's not what Colahan calls it, of course. To her, the board's blue dots (boy lions) and red dots (girl lions) represent serious business. As the Species Survival Plan coordinator for African lions in a hundred zoos across the country, Colahan oversees the process of pairing genetically diverse blue dots and red dots to make white dots, or lion cubs.

See also: Red kangaroos have three vaginas, and other weird facts about animals' love lives

"If there's a B in the box, there's a breeding recommendation," Colahan says, pointing to a neat grid in which each box signifies a different zoo. The boxes are filled with dots to indicate lions in residence; in some of the boxes, Colahan has scribbled notes such as "making exhibit modifications" or "can't take more cats right now." It may not look super-sexy, but the Association of Zoos and Aquariums believes such data is necessary if American zoos are to maintain a healthy and sustainable (read: not inbred) population of captive African lions. And that's important, because African lions are disappearing from the wild.

"It's not just a matter of 'We want lion cubs because they're cute,'" explains Colahan, whose official title at the zoo is Curator of Large Mammals. The bigger goal, she says, is to make sure that the entire zoo population is viable one hundred years from now. And that won't happen if the animals are allowed to get all Flowers in the Attic and start lusting after their siblings because they've been locked in this attic together for years. So great pains are taken to transport animals across the country — sometimes in the cargo bays of commercial flights! — to breed with other animals that aren't their brothers or sisters.

"We prioritize breeding the animals that have the fewest relatives in the population," Colahan notes. "We use this analogy [of] online dating and matching animals up — and those are the pieces we're looking at: Where are they, genetically, in the population?"

In other words, Colahan and her ilk don't care which lion has the fluffiest mane or which are social drinkers and non-smokers except if they're drinking. What makes an animal truly valuable in the eyes of zoo matchmakers is if it's unrelated to any other captive animal.

According to Candice Dorsey, the AZA's director of animal programs, there are Species Survival Plans for more than 500 animals, ranging from tarantulas to tigers. Each of those species also has a coordinator who volunteers (coordinators don't get paid for their work) to keep a "stud book" that lists all of the eligible — and ineligible — males and females. Several things could make an animal ineligible: if it's related to too many other animals or is too old to breed, for example, or if it's so ornery that it would rather fight than fornicate.

Colahan and her AZA colleagues develop a Breeding and Transfer Plan each year that lays out how many baby lions should be born to offset the number of older lions that are expected to die. "We create these life tables that are like what actuarial scientists use for life-insurance companies," Colahan says. The baby-lion goal "is sort of a moving target, depending on what's going on with the population."

Once Colahan has that number, she begins coordinating the babymaking. She works with zookeepers around the country to figure out which lions should breed with which lionesses. In addition to an animal's genes, they consider several other factors, such as personality and age. It's easier to make the first introduction between a male and a female when they're young, she explains; by the time lions are older, they're more set in their ways.

So how do you tell if two lions will get along? It starts with that introduction. "We bring them in and let them see each other first," Colahan explains. "And then, typically, they can get close to each other with a barrier in between, like a fence, and we can gauge how they're reacting. Do they seem like they really want to be together? Do they seem like they want to eat each other?.... There's usually a lot of noise and a lot of chasing each other around."

Although some big cats, like leopards, have been known to kill each other when introduced, that's rare with lions, Colahan notes, because lions are social by nature. "It's fairly unusual, but it does happen," she admits. "They're large predators, and they're certainly capable of causing serious injuries. That's what we look at when we do introductions: Is this just swatting each other on the nose and sorting out who's boss? Or is this really serious, and these guys don't want to spend any time together?"

Most of the time, she says, "If you put a boy and a girl lion together...they produce cubs." Colahan explains the process, in a very science-y way that still manages to sound like something out of Fifty Shades of Grey: "The female becomes very solicitous, and she'll come up to him and rub on him and lay down. And then the male will mount her, and, typically, he might bite the back of her neck. And then when they're done, she spins around and snarls and jumps at him. And then they stop for a little bit and then they'll start back up again. With lions, they'll breed multiple times in a day. It's kind of nonstop." Until the female comes out of heat, at least.

If a particular pair is too successful — that is, if they keep popping out cubs like it's their job — Colahan will shut that down. The most common form of birth control is a shot given to a lioness that prevents her from becoming pregnant for about two years. One of the main reasons for such contraception is logistical: The 100 zoos that Colahan currently works with can hold just 320 lions. "If we just bred everything as much as we could, then we'd very quickly run out of space," she says.

Colahan is not the only Species Survival Plan coordinator at the Denver Zoo. Rick Haeffner, the zoo's Curator of Reptiles and Fishes, is the AZA stud-book keeper for three species: black-breasted leaf turtles, Sulawesi forest turtles and Komodo dragons.

Of the three, Komodo dragons are the most badass. Consider these facts: Komodo dragons are giant lizards that can grow up to ten feet long; their saliva is toxic, and in the wild, they eat feral dogs. In the movie Skyfall, James Bond fights a bad guy in a Komodo dragon pit, and the dragon finishes the job. A male Komodo dragon has a two-headed penis, and a female is capable of virgin birth: Even if there are no males around, a female can lay a clutch of eggs. All of the babies in such cases are born male, which scientists think is so that their mother can mate with them and preserve her genetic line rather than have it die out for lack of a good two-headed penis.

The world's largest indoor Komodo dragon habitat is housed within the Denver Zoo's Tropical Discovery exhibit and is home to four dragons: males Castor and Raja and females Anika and Kristika, who came to the zoo last year from Prague. Though they're still too young to breed, the girls are especially valuable, because they're genetically diverse.

Komodo dragons are native to just a few small islands in Indonesia; it's estimated that only about 3,000 are left in the wild. In the captive AZA population that Haeffner manages, there are 71 males, 56 females and one dragon whose sex is unknown. The biggest challenge that Haeffner faces as the official overseer of dragon breeding — the Hagrid of the Association of Zoos and Aquariums, if you will — is evening out the sexes.

"The population really needs females," he says.

But a recent scientific breakthrough could help: Last year, the Los Angeles Zoo used a technique originally developed to determine the sex of baby birds before they hatch to do the same for Komodo dragons. The process involves inserting a tiny needle into a leathery dragon egg to extract blood from the still-developing embryo and then conducting a DNA test to determine the embryo's sex. The L.A. Zoo was able to identify which embryos were female, Haeffner explains, and then only allow the female eggs to continue incubating and eventually hatch.

If that kind of gender discrimination sounds harsh, contemplate this: Komodo dragons are solitary creatures that can live more than thirty years. While baby dragons can be fun and even — dare we say it — cute, there just isn't enough space in AZA zoos to hatch every egg that's laid.

How do Komodo dragons get to the egg-laying stage? By performing a mating ritual that Haeffner calls "not very exciting" — in the manner of a reptile keeper used to seeing claw-raking, two-headed-penis sex. One female dragon once lost an eye because the male was so aggressive.

"The prelude is pretty intense," Haeffner says. "He rakes her sides; he'll bite her." If the female isn't ovulating, she won't be interested. But if she is, she'll lay down next to him, lift her tail and sometimes even drape it over him. He'll deploy his genitalia, usually kept tucked away in his cloaca, and use one of his two "hemipenes" to do the deed.

"With most dragons, even somewhat aggressive ones, he and the female are so focused in on this breeding thing that you can actually go in and sit practically right next to them," Haeffner says. And he should know, because he's overseen three successful breedings at the Denver Zoo. "I was able to go in and get down on my hands and knees and look," he says. Just one of the successful breeder dragons remains at the zoo.

The last time the Denver Zoo had lion cubs was in 2006. That year, male lion Krueger sired two cubs, Razi and Zuri, with lioness Baby. The year before, the pair produced one cub, Asali. Both mother and father were on a breeding loan from the Columbus Zoo in Ohio, per the recommendation of the Species Survival Plan. (This was before Colahan became the coordinator.) After Razi and Zuri were born, Denver stopped breeding because of space constraints, and according to Colahan, the lions "just never started back up again. They got older during that time period, and we haven't had any babies since."

Baby ended up staying in Denver; Krueger, an older lion, died last year, and the cubs were sent to other zoos. But the Denver Zoo has since taken in three other lions: males Rajah and Sango and female Sabi. She and two of her brothers came to Denver in 2012 as cubs from Qatar, where they previously belonged to the royal family. The males have since moved elsewhere, but all three are considered prime breeding candidates because they're not related to any other animals on the Magnetic Whiteboard of Lion Sex. We predict lots of the latter in Sabi's future.

Hollie Colahan manages mammals — and matches — at the Denver Zoo.
Denver Zoo