Senses being tapped to keep the predators clear of cattle
By SUSAN MONTOYA BRYAN
ALBUQUERQUE – Wildlife managers are running out of options when it comes to helping Mexican gray wolves overcome hurdles that have thwarted reintroduction into their historic range in the Southwest.
Harassment and rubber bullets haven’t worked, so they’re trying something new – a food therapy that has the potential to make the wolves queasy enough to never want anything to do with cattle again.
As in people, the memories associated with eating a bad meal are rooted in the brain stem, triggered any time associated sights and smells pulse their way through the nervous system.
Wildlife managers are trying to tap into that physiological response in the wolves, hoping that feeding them beef laced with an odorless and tasteless medication will make them ill enough to kill their appetite for livestock.
Cattle depredations throughout southwestern New Mexico and southeastern Arizona have served as an Achilles’ heel for the federal government’s efforts to return the wolves.
Conditioned taste aversion – the technical term for what amounts to a simple reaction – is not a silver bullet for boosting the recovery of the Mexican wolf, but some biologists see it as one of few options remaining for getting the program back on track after nearly 14 years of stumbling.
“Just the very fact that the U.S. Fish and Wildlife Service is trying something new ought to send the message that they really are seriously concerned about the ranchers’ concerns,” said Dan Moriarty, a professor and chairman of the psychological sciences department at the University of San Diego.
“We have to find a way to sort of peacefully co-exist,” said Moriarty, who has worked with captive wolves in California. “That’s my hope, that the taste aversion will be one more tool.”
Gray wolves have rebounded from widespread extermination throughout the Northern Rockies and the Great Lakes region. Since being declared endangered in 1974, the wolf population has grown fivefold – to about 6,200 animals wandering parts of 10 states outside Alaska.
After four decades and tens of millions of dollars, the federal government was recently able to remove the animals from the endangered species list in several states.
The case is much different in the Southwest, where the population of the Mexican wolf – a subspecies of the gray wolf – continues to be about 50 despite more than a decade of work. Biologists had hoped to have more than 100 wolves in the wild by 2006.
Due to livestock problems, about 90 wolves and some dependent pups have been removed – in some cases lethally – from the wild since the program began. For about four years, the Fish and Wildlife Service operated under a policy that called for trapping or shooting wolves if they had been involved in at least three cattle depredations.
The agency has since scrapped the policy, and ranchers have all but given up on keeping track of their dead cows and calves.
In the last year, monthly reports from the wolf program show wildlife managers investigated four dozen depredations in Arizona and New Mexico. They determined that wolves were involved in half of the cases.
Caren Cowan, executive director of the New Mexico Cattle Grower’s Association, said ranchers are frustrated.
“You really have no idea how bad it is when a dad calls you and says ‘There’s a wolf in my yard and my kids and my wife are stuck in the house. What can you do to help me?’”
That’s the issue, Cowan said. “These animals are habituated to humans and until we can figure that out, I don’t know what you do.”
Cowan acknowledged, however, that getting wolves to stop preying on livestock would be a huge first step.
Biologists working at a captive breeding center at the Sevilleta National Wildlife Refuge in south-central New Mexico treated six wolves last April and another two in October. The animals were fed baits made up of beef, cow hide and an odorless, tasteless deworming medication that makes the wolves queasy.
Fish and Wildlife Service biologist Susan Dicks said the initial tests appear to be successful, with the wolves not wanting anything to do with the beef baits after their first serving.
The idea is that when wolves smell cattle in the wild, their nervous system and brain stem will kick into gear and override any desire they have to get near the cattle.
“We’re learning as we go, but so far we have seen some good aversions produced,” Dicks said. “Again, it’s impossible to say yet whether this translates to a livestock animal running around on the hoof.”
Wolf releases have been put off for the past year, and it’s unclear whether the agency will have the opportunity to release the treated wolves this year so the taste aversion treatments can be fully tested.
The work done with the Mexican wolves is based on decades of research conducted by Lowell Nicolaus, a retired biology professor from Northern Illinois University. He has seen it work with captive wolves and free-ranging raccoons and crows.
“It just takes one good illness,” said Nicolaus of Butte Falls, Ore. “Their avoidance is going to be expressed wherever they see the food or smell it. It doesn’t depend on when and where they first ate it or when and where they got sick.”
Nicolaus said taste aversion works because it’s an unconscious response, not a threat that wolves can overcome such as being hazed or shot at with rubber bullets.
The other benefit is biologists say wolves that have an aversion to cattle are likely to pass that on to their pups by teaching them hunting habitats that avoid cattle and focus on deer, elk and other native prey. They call that a feeding tradition.
Bill Given, a wildlife biologist who helped the Fish and Wildlife Service with the first batch of wolf treatments at Sevilleta, describes taste aversion as a natural solution that taps into an evolutionary defense mechanism that is common among all animals.
“You can build a great fence or you can have a dog as a shepherd, but none of those things can change the desire to consume the livestock,” he said. “They just make it challenging and then the predator has to work around that barrier.”
To ranchers, the wolves are “killing machines,” Cowan said.
The biologists don’t necessarily disagree.
“There’s no stopping the feeding and the sex drive. All life is about those two things,” Given said, noting that wildlife managers have an opportunity to gain some control through taste aversion.
The next challenge will be proving its value on the range by monitoring wolves that have been treated.
“I think it does have a lot of promise,” Dicks said. “And part of it is we’re willing to try anything to get these animals successfully on the ground without impacting livestock growers.”