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Birds, bees do it; zoo animals not so much

Oregon Zoo scientists play mating games to enourage breeding


by: PHOTO COURTESY OF PANDAS INTERNATIONAL - Oregon Zoo researcher Meghan Martin discovered that allowing female pygmy rabbits to choose their mates  produced more offspring. Now shes in China (above), trying out her techniques on giant pandas. Each female pandas enclosure sits next to two pens holding male pandas.Imagine, for a moment, you’re a pygmy rabbit. A Columbia Basin pygmy — tiny, genetically different than all other rabbits, and endangered.

In the wild, you mate like, well, a rabbit. Or you used to. But most of your Eastern Washington habitat has been taken by agriculture, so your species’ only chance for survival is captive breeding.

Scientists at the Oregon Zoo have tried nearly everything to get you (you’re female) and your few remaining female friends to breed at their facility in Clackamas County. They’ve constructed really nice cages and placed you in them with males they’ve chosen based on their genetic variation, so that if you have offspring, they will be genetically diverse. Yet you refuse to breed in captivity at anything like the rate you did in the wild — just like most of the endangered species that scientists have been trying to breed in zoos around the world.

What is it that you want, pygmy rabbit?

Meghan Martin, a researcher at the Oregon Zoo, had an idea. Maybe you want to choose your mate, rather than have zookeepers select the ideal genetic mate for you. So she and the zoo’s Director of Conservation David Shepherdson conducted an experiment that just might change the way zoos and breeding operations around the world do business.

Martin placed you, female pygmy rabbit, in a cage. She surrounded your cage with three abutting cages, each containing a male pygmy rabbit. In what zoo officials are referring to as a “speed-dating program” that actually lasted a few weeks, she let you choose which of the three males you might prefer placed in your cage. When you started rubbing heads through the fencing with one particular male and running parallel to him along the barrier, they figured you had made your choice.

The scientists let you have alone-time in your cage with your chosen mate, but for the sake of scientific research, they also paired other females with males they hadn’t chosen, and other males with other females who had not spent a few weeks as caged neighbors.

About a month later, Martin watched to see how you all had done. Not surprisingly, she discovered that when you were allowed to mate with males you had chosen, you were more likely to produce offspring than in any other type of situation. She also found that mating you with a neighbor rabbit you had not chosen worked better than when you were placed in a cage with a stranger.

Also, females paired with preferred males and neighbors had larger litters than they did with strangers.

Familiarity breeds content

OK so you want to choose a mate. Makes sense. But what may be the most puzzling piece of the experiment was revealed a year later. Twenty kits born to couples who had spent a week as neighbors (and in some cases chosen each other) survived. Only two kits born to rabbits paired as strangers survived.

All of which says that, maybe, zoos have been taking the wrong approach all along in deciding which animals to match up for mating. Making genetic diversity the first priority may have been missing something you and your animal mates already knew how to handle.

“In the wild, every one of these animals has mate choice,” Martin says. “The way we were going was just genetic based. It baffled me. You wouldn’t expect two humans thrown into a room together to have a baby. Why do we expect that from endangered species?”

Shepherdson says reproductive biology for endangered species is a relatively new and little-studied piece of captive breeding programs. In the lab, he says, female mice that were mated with preferred males have produced better offspring than when they were paired with strangers. The Oregon Zoo experiment has simply taken the idea one step out of the lab and into the field with wild animals.

Which doesn’t mean Martin and Shepherdson know why female pygmy rabbits that were mated with neighbors and chosen males produce more and healthier offspring. It may be, Shepherdson says, that the rabbits simply feel more comfortable mating with someone they know. Maybe, he says, the few weeks of familiarity help the female feel safer.

“Maybe the male you know is less likely to attack you,” he says.

Another possibility, according to Shepherdson, is that the genetic markers scientists use to match males with females don’t tell a complete story.

“It is conceivable (the rabbits) actually have a better idea of what a genetically suitable partner is,” Shepherdson says.

As for why the rabbits from couples who had been neighbors ended up healthier, Shepherdson says he has no answer, but he’s certain there is one. “There must be an adaptive reason,” he says.

Zoos shift focus

The future of zoos around the world may depend on scientists figuring out the answers to these questions. More than 90 percent of zoo animals are born in zoos. There just aren’t many exotic species left to capture in the wild. And that means the survival of many of these species depends on what happens in the zoos’ captive breeding programs.

The San Diego Zoo has one of the nation’s largest breeding programs, and figuring out techniques to encourage mating has become a major emphasis, says Chief Life Science Officer Robert Wiese.

Cheetahs, for instance, present a problem because there are so few in captivity. Letting one female choose one male to mate with won’t yield enough genetic diversity for a healthy future cheetah population. Scientists at the San Diego Zoo Institute for Conservation Research needed to find a way to get females to mate with many males.

Just putting a female together with many males didn’t work. She would only mate with her chosen male. But when they made a recording of the chosen male’s mating cry and played it continuously through a speaker in the female’s cage, she became willing to mate with other males.

“We’re not sure how it helps, but when we play this call back we can get the female to be responsive to males she was not responsive to before,” Wiese says.

Scientists at the San Diego and Portland zoos have been trying to encourage California condors to mate since the early ‘80s, when their population in the wild dwindled to 22, all in zoos. The problem, Wiese says, was that condors only breed one chick every two years, which wasn’t enough to build up the population.

The solution, used at both zoos, has involved a little sleight of hand. As soon as a female condor lays an egg, scientists remove it from the nest to hatch it in an incubator. The female on the now empty nest would then lay another egg. Some condors have now produced two or three chicks a year instead of one every two years.

But a condor was needed to raise the incubator chicks in a way that they would adapt in the wild. The solution has been hand-held condor puppets, which feed the birds through their beaks just like momma condors.

At the Oregon Zoo facility in Clackamas, scientists have discovered they get more offspring from condor couples if their pens are placed next to other pens with breeding pairs.

“It appears when they see them getting it on in one pen, they are more likely to get it on themselves,” Shepherdson says.

Shoebill storks have never been successfully bred in zoos, according to Wiese. And flamingos rarely have — they need to be in groups of at least 20 or 30 before they will produce offspring. In the wild, both animals live in large flocks. Maybe, Wiese says, the smaller flocks in zoos just don’t give the birds enough sense of security to feel comfortable breeding.

Desert dwelling spay-toed frogs in the wild stay underground 10 months of the year and only come out and breed when it rains. San Diego Zoo scientists figured out that they didn’t actually need the rain, however, just the sound of rain. They made a recording of rain, played it through speakers in the frog exhibit, and the frogs came out and produced offspring.

Males have a say

Giant pandas haven’t been so easy, despite efforts to get this signature species to breed in captivity. That’s why Meghan Martin of the Oregon Zoo has headed to the Bifengxia Panda Reserve in Ya’an, China. She’s using her speed-dating technique on 26 pandas there, where breeding rates have historically been low. And she’s made a new discovery — sometimes the male may need to make the choice.

Martin has set up the giant pandas in six cages, segregated by sex. Each female has males on two sides. Martin is looking for signs that the pandas have mating preferences. It isn’t hard to find those signs.

The male pandas show an interest in females, Martin says, by doing handstands against a wall next to her cage while urinating. The males also make a distinctive “come hither” call. The females show interest by putting their tails up, arching their backs, and backing toward the males so the males can sniff their genitalia.

“It’s a pretty cool behavior,” says Martin, who has been traveling back and forth to China for more than a year.

Pandas don’t appear to be exactly like pygmy rabbits when it comes to mating preferences. Last year’s panda pairings where both pandas chose each other produced offspring. But pairings that involved females choosing males who did not choose them produced no offspring. Yet in cases where a male panda showed interest in a female and the females did not reciprocate, baby pandas were the result every time.

All of which means, Martin says, that different species have different mating behaviors that scientists need to uncover. She’s certain that letting animals choose their mates is an important first step.

“I’m sure it’s having an effect on almost every species in captivity,” she says.


Bigger is better for breeding

Size matters, say scientists at the Oregon Zoo as well as other breeding facilities around the country. The size of animal enclosures, that is. Larger breeding grounds, they say, are critical to developing sustainable populations of exotic animals.

In the wild, elephants form matriarchal herds with a mix of ages, says David Shepherdson, Oregon Zoo director of conservation. Young females and males observe older elephants breeding, which might be important, but isn’t possible to replicate in small zoo enclosures. Flamingos in the wild often stay in flocks with thousands of other flamingos and go through complicated mating rituals — again impossible in zoos.

The solution increasingly is for zoos to establish separate large breeding facilities, off-limits to the public. In December, Metro approved about $1 million in bond spending to buy the Roslyn Lake property near Sandy. Once the property is ready, a herd of three to five female elephants and one male will have 240 acres to roam, set up more natural social structures, and potentially breed, away from the prying eyes of zoo visitors. Other species may be sent to the facility for a more natural breeding experience.