Researchers study contraception as a potential coyote management tool

Aug 10, 2012

Talk to almost anyone who raises sheep in Wyoming, and they’ll tell you they’ve had problems with coyotes.  Traditionally, the response has been to kill the coyotes, often by aerial gunning. But researchers at the University of Wyoming are trying to come up with an alternative management tool, which they hope will work better in the long-term and be more  humane. Wyoming Public Radio’s Willow Belden reports.

WILLOW BELDEN: It’s a windy morning, and just outside Laramie, a group of bushy-tailed coyotes trot in circles around their chain-link kennels. They’re all young males, and half of them have been given a high dose of the drug Deslorelin, which is meant to make them sterile. Marjie MacGregor, a PhD student at UW, is running the study. She and her assistant sedate one of the coyotes with a syringe and carry it inside to a lab.

MacGregor gently lays the animal on an exam table.

MARJIE MACGREGOR: His name is Gonzo, and he is an experimental coyote. He was given forty-seven milligrams of Deslorelin.

BELDEN: MacGregor takes Gonzo’s temperature, weighs him, draws some blood, and then uses a pair of calipers to measure the coyote’s testes.

MACGREGOR: Fourteen-point-seven. And ten-point-six for the left. … This is just telling us the volume of the testes. Because when they’re producing high levels of testosterone, they’re producing high levels of sperm, and their testes are going to increase in size.

BELDEN: In other words, measuring the testes tells MacGregor whether the drug is actually working. The other tests she’s running screen for side effects.

The goal behind the whole project is to come up with a more effective way to keep coyotes from killing sheep.

DONAL SKINNER: Our current methods of controlling the coyote populations aren’t working.

BELDEN: That’s Donal Skinner, who’s working with MacGregor on her project. He’s a professor of zoology and physiology at the University of Wyoming, and he specializes in regulating reproduction.

SKINNER: There is only really one method, and that is to cull coyotes. And across the United States, an enormous number of coyotes are culled every single year.

BELDEN: What culling means is killing the coyotes. Wildlife Services does it by aerial gunning the animals. And local predator management groups shoot or trap coyotes that end up on ranches.

In 2010, more than 80,000 coyotes were killed nation-wide, about 8,000 of which were in Wyoming. Yet coyote populations are growing, not shrinking. That’s because as more coyotes are killed, the remaining animals produce greater numbers of offspring.

MacGregor says that means livestock aren’t any safer – at least not long-term.

MACGREGOR: When you go in and remove a depredating pair of adult coyotes, it takes just a relatively short time – maybe three months – for a new pair of coyotes to move into that vacant territory and begin resuming depredations.

BELDEN: Plus, she says, killing coyotes disrupts the ecosystem. So her idea is not to get rid of the coyotes, but to take away their incentive to go after sheep.

MACGREGOR: Twenty years ago they started looking at research that showed that if you removed puppies, that depredations decreased.

BELDEN: In other words, if a pair of coyotes has no babies, they don’t need as much food, so they’re apt to eat smaller wildlife, rather than livestock. MacGregor hopes that by sterilizing “problem” coyotes and preventing them from reproducing, you could get coyotes and livestock to live in harmony.

Some Wyoming sheep producers, like Catherine Wissner of Carpenter, like the idea.

CATHERINE WISSNER: I really don’t want to use lethal methods, because I’ve got a couple cows and some other animals. And also the houses are starting to encroach a little closer to the ranch, so there isn’t really a good, clean, clear shot to take at a coyote anymore. I don’t want to trap them, and I don’t want to poison them, because I don’t want the poison in the environment.

BELDEN: Wissner says contraception seems like a good alternative. But others ranchers disagree. They say the idea is too risky, and prefer to have the predators killed.

MacGregor’s project faces opposition from the other side too.

BROOKS FAHY: Coyotes are a native species, and let’s just leave well enough alone.

BELDEN: That’s Brooks Fahy with the group Predator Defense.

FAHY: Nature has a synchronicity to it, and when it really gets screwed up is when human beings try to control it and manipulate it. And that’s what you’re talking about here.

BELDEN: Still, some ecologists applaud the research. Bob Crabtree heads the Yellowstone Ecological Research Center and has been studying coyotes for decades. He says any non-lethal control method is worthy of consideration, though he says it would be very difficult to make sterilization work, because the process could disrupt the coyotes’ pack dynamics.

BOB CRABTREE: You know there’s a lot of competition to become alpha male. And those alpha males are the ones that exclusively do the breeding and produce pups. And sterilization could cause the alpha male to lose his status. So if you don’t do it right, it doesn’t work, because then another individual that’s not sterile will take its place and breed.

BELDEN: Still, MacGregor is optimistic that there is a way to make this work. She’ll continue monitoring her test coyotes for some time, and if she’s happy with how the drug is working, she plans to talk with ranchers to get permission to run some studies in the field. For Wyoming Public Radio, I’m Willow Belden.