July 9, 2014
Loss Of A Breeding Wolf Can Be Devastating, But Does Not Always Spell Doom For The Pack
Brett Smith for redOrbit.com - Your Universe Online
The loss of a breeding wolf can be a devastating event for a wolf pack, but a new study shows it may not spell the end, according to a recent statement from the Institute of Arctic Biology at the University of Alaska, Fairbanks.
According to a new report in the Journal of Animal Ecology, the sex of the dead wolf and the size of its pack can determine whether that pack forges on or collapses.
The new study was partially inspired by a drop in wolf sightings after the death of a mating female from a pack that lived near Denali National Park in Alaska. This was one of many instances where the death of a specific wolf from legal trapping or hunting led to widespread attention in the past several years.
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“This isn’t the first time we have noticed that the loss of a breeding wolf can affect the fate of the pack. We thought it would be valuable to systematically look at what happens to the pack and population following the death of a breeder,” said study author Bridget Borg, a National Park Service biologist.
The study team looked into reproduction and population growth impacts of a breeder death as well as a pack’s ultimate fate.
“Given the park’s current low wolf densities and small average pack sizes, we are concerned about harvest of wolves from packs that reside primarily within the park,” said Don Striker, superintendent of Denali National Park and Preserve. “The death of a breeding wolf could harm the packs that provide the greatest opportunities for park visitors to see a wolf in the wild, either through a lack of reproduction or the loss of the entire pack.”
The study team analyzed information amassed on 70 wolf packs during long-term study of wolves in the Alaskan park. They discovered that although breeder death preceded or coincided with 77 percent of the cases where packs were no longer around, the death of a mating individual did not always result in the end of a pack. In around two out of three cases where a breeder died, the pack survived.
“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 said. “The probability of a pack continuing was less if a female died or if the pack was small prior to the death.”
The study team also said the death of a breeder has a greater impact on a pack if the wolf passed away before or during the breeding season.
“We noticed that human-caused mortality rates were highest during the winter and spring, which correspond to the pre-breeding and breeding seasons for wolves,” said study author Laura Prugh, a wildlife ecologist at the UAF Institute of Arctic Biology. “Harvest may lower the odds of pack survival because of this timing, especially when pack sizes are small.”
The researchers noted that greater rates of breeder fatality and pack disruption did not match lower population growth, implying that the wolf population was able to endure the loss of mating individuals at a population level. They show that wolves may make up for the death of breeders in a wide variety of ways, such as quick replacement of breeders or boosted reproductive success the next year.