National Wildlife Refuge System

Special Delivery: Wildlife

Caribou are being flown to Kenai National Wildlife Refuge, AK.
Credit: USFWS

Caution: Saving a species may require heavy lifting – literally picking up wild animals and moving them long distances. Big animals. Small animals. Skittish, furtive or aggressive animals. Regardless, the same biological rules apply: To better the odds of survival, rare species need more than one population base and the widest gene pool possible.

This spring, Northwesterners got a glimpse of the challenges involved when U. S, Fish and Wildlife Service staff netted, sedated and trucked 49 endangered Columbian white-tailed deer from Julia Butler Hansen Refuge for the Columbian White-Tailed Deer to Ridgefield National Wildlife Refuge, 60 miles southeast in Washington state. The deer were moved to protect them from the threat posed by an eroding dike between the Columbia River and Hansen Refuge: If the dike failed, flooding might otherwise wipe out the species. A few deer were even flown a short distance by helicopter, suspended by slings. 

Because national wildlife refuges protect hundreds of rare species, they often find themselves in the animal moving business. They’ve been in it at least since 1907 when the Service transported 15 native Plains bison by rail from the New York Zoological Society to Wichita Mountains Wildlife Refuge in Oklahoma. The animals “were the seed stock for the bison we manage here today,” says refuge manager Tony Booth.  

Wildlife conservationists don’t move animals casually. “Anytime you capture an animal and move it, there’s a risk,” says Kate O’Brien, a wildlife biologist at Rachel Carson National Wildlife Refuge in Maine, part of a coalition working to relocate and captive-breed the increasingly rare New England cottontail. “You have to consider: Does the benefit outweigh the risk? You need a pretty good reason to move a wild mammal.”

Refuge biologists have lots of good reasons. They “translocate” wild animals to breed them; reintroduce them to historic habitats; try to keep them off the “endangered” list; minimize unfriendly run-ins with humans; rescue them from disease, drought or development; introduce them to areas where climate warming is creating new habitat. “The first choice is always to protect existing habitat,” says O’Brien, “but that can’t always be done.”

You think moving deer is tricky? Try moving 800-pound Alaska brown bears (with a bad habit of raiding campgrounds) or 600-pound caribou (flown 300 miles from Nelchina to Kenai National Wildlife Refuge on the Kenai Peninsula, where they’d previously been extirpated). In cases involving these and other large carnivores such as panthers and wolves, the first trick is catching them while minimizing risk to wildlife and operations staff.

Smaller mammals - prairie dogs, rabbits, squirrels, pronghorn – are easier to capture, but high-strung and must be released quickly to avoid stress injuries. Timing matters. Rabbits are “easiest to trap in winter, when food is limited and you can see their trails in the snow,” says O’Brien.

Also, “you want to “trap them before breeding season. You don’t want disturb them if they’re pregnant or have young.”

When endangered species are involved, operational hurdles include the preparation, publication and review of detailed project proposals. It took three years of such effort before staff could move 24 endangered Sonoran pronghorn 90 miles from Cabeza Prieta National Wildlife Refuge to Kofa National Wildlife Refuge in Arizona in 2011 and 2012. The final rule, says Jim Atkinson, a wildlife biologist at Cabeza Prieta Refuge, “spells out what we can do and where, and how it will affect all stakeholders.” The project goal: to augment the existing pronghorn population through captive breeding and establish new populations in the animals’ historic breeding range. “We don’t want to have all our eggs in one basket,” says Atkinson. “It’s a hedge against bad years for drought or climate change in any one area. Having more than one population means a greater hedge against extinction.”

Tagging lets biologists track the health and movement of animals after their return to the wild.
Once pronghorn are caught and sedated, for example, biologists attach an ear-tag and radio collar.

Where tagging is too costly or labor-intensive – as it is with prairie dogs – scientists find other ways to follow transplants. Staff at Charles M. Russell National Wildlife Refuge in Montana have relocated more than 2,600 prairie dogs. In 2007, they moved 800 to repopulate colonies after an outbreak of plague – a recurrent prairie dog threat. Leaving them where they were would have doomed the colony, says senior refuge wildlife biologist Randy Matchett. It also would have hurt other species that depend on prairie dogs, such as endangered black-footed ferrets. (When you’re a predator, you’re only as healthy as your prey.)

Captured prairie dogs were dusted for plague-carrying fleas, then trucked to a new site, pre-dug with underground burrows. There, cages protected them for three or four days while they acclimated. Then they were released in groups of 100 or more. “Because they are social animals and communicate with each other, we’ve learned they do better in large numbers,” says Matchett. “Their whole life revolves around not being eaten.”

Will the new colony succeed? Measurements will provide an answer. “We can map the colony by walking around the perimeter of all the burrows,” Matchett says. A year from now, a healthy colony will occupy more space. But there’s a caveat: Even if the colony thrives, Matchett knows it’s just a matter of time before plague reappears and he must rescue the animals again.

That’s the age-old challenge for wildlife conservationists: staying ahead of threats, when possible. And knowing when it’s not. Alaska brown bears offer a lesson in the latter. Brown bears that raid campgrounds are being moved less these days, says John Morton, supervisory fish and wildlife biologist in Alaska. “We realize that even when we move them a long ways away, they will still come back.”

Last updated: June 5, 2013