Chisana Caribou Recovery Project

The Chisana herd is a small, genetically distinct, population of caribou inhabiting eastcentral Alaska and southwest Yukon. The herd summers almost entirely in Wrangle-St. Elias National Park and Preserve in Alaska. Much of the herd’s winter range falls within Kluane Wildlife Sanctuary. Historically the herd numbered as high as 3,000 animals in the early 1960’s. Since 1989 the herd has declined from about 1,800 to less than 700 animals in fall 2003.

The decline in the population of Chisana caribou was caused by high predator success. Predators of the herd include not only wolves, but also bears and eagles preying on calves. With few calves surviving and the adult caribou aging beyond their prime reproductive years, the herd faced catastrophic decline.

The direction given through public consultations in Beaver Creek, Yukon and Tok, Alaska was for wildlife managers to intervene proactively, before a drastic drop in population further limited the potential for recovery. The challenge was to find an acceptable way to relieve predation on the Chisana herd calves.

A Chisana Recovery Team was established, including all key international resource management agencies, the White River First Nation, the Yukon Fish and Wildlife Management Board, and other community and conservation organizations. Representatives began meeting in spring 2002 to provide direction for recovery efforts. White River First Nation formally expressed its support for all measures necessary to protect and recover the herd, including restricting all harvesting and a ‘captive-rearing’ project on the herds range.

The first ‘captive-rearing’ project to increase calf survival was carried out in March 2003. At a facility developed on the herd’s Yukon winter range, 17 pregnant Chisana caribou were captured and held in a compound to keep them safe from predators. The caribou were released from the compound in June when calves were better able to escape predation.

‘Captive reared’ caribou had a 70% calf survival rate the following fall when calves were 5 month-olds and had much greater certainty of living to adulthood. This compared to only 13% calf survival among the sample of radio-collared free-ranging females.

The team decided to continue with a larger scale project in 2004, capturing 29 pregnant cows. There was a 76% calf survival rate for ‘captive reared’ caribou compared to only 14% among free-ranging. An even larger scale project with 50 pregnant cows took place in 2005.

‘Captive-rearing’ on a herd’s natural range has distinct advantages over captive-breeding at a facility by overcoming difficulties with caribou anti-predation behavior, genetic composition, disease exposure, costs and public acceptance. Other methods of reducing predation on the herd such as predator control are impractical because it is a transboundary
population ranging in Wrangle-St. Elias Park in Alaska and Kluane Wildlife
Sanctuary in Yukon.

‘Captive rearing’ can make a difference to Chisana herd population size and structure and will likely lead to the herd being removed from its ‘at risk’ listing. The experiment also holds potential for recovering other small and threatened caribou populations throughout North America.