Wolf Populations are Unfazed by Individual Breeder Deaths

General wolf population numbers surprisingly appear unaffected by the occasional death of key breeders. Even while these deaths might mean the end of specific packs, researchers have found that recovering wolf populations somehow compensate for brief losses.

In a surprising number of classic Disney movies, the main characters appear to persevere even in the absence of parents long dead or simply not in the picture. This Bambi-eske phenomenon has surprisingly been seen for general wolf populations as well, in which the death of head mother and father wolves barely affect overall population numbers, despite the potential dissolution of a pack.

According to a study published in the Journal of Animal Ecology, researchers theorized that even the accidental or legal death of a single primary breeder could have disastrous impacts on wolf packs and populations.

"We thought it would be valuable to systematically look at what happens to the pack and population following the death of a breeder," study author Bridget Borg, a National Park Service biologist, said in a statement.

Borg and her colleagues reportedly set out to determine what kind of impact these deaths can have after several individual deaths led to the apparent disappearance of entire packs in Alaska's Denali National Park and Preserve.

They examined data collected on 70 packs in the preserve and quickly found that breeder deaths were associated with 77 percent of all disappearing packs. However, among all packs that lost a breeder, two in every three managed to continue.

"It appears that the sex of the breeder that was lost and the size of the pack prior to that loss were important factors explaining pack fate following the death of a breeder," Borg explained. "The probability of a pack continuing was less if a female died or if the pack was small prior to the death."

These results, while predictable, also led to the surprising discovery. Despite pack disappearances from breeder death, total wolf numbers remained largely the same from year to year.

The authors suggest that wolves may compensate for the death of breeders with increased attention to reproductive success the following year. Wolves from dissolved packs also may leave to join others or start their own, becoming primary breeders themselves.

The study was published in the Journal of Animal Ecology on July 7.