考研英语阅读篇章母狼的死亡威胁种群生存

　　篇章：母狼的死亡威胁种群生存

　　When a breeding wolf dies, its sex and the size of its pack can determine whether that pack continues, according to research published July online by the Journal of Animal Ecology. In 2012, biologists at Denali National Park and Preserve noted a drop in wolf sightings following the death of a breeding female from a pack that lived along the Denali Park Road. This was one of several instances where the death of an individual wolf from legal trapping or hunting sparked widespread attention in recent years.

　　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 author Bridget Borg, a University of Alaska Fairbanks biology graduate student and National Park Service biologist.

　　Borg s research looked at changes in wolf pack fate, reproduction and population growth following the death of breeders.

　　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.

　　Gray wolves typically live in packs consisting of the parents and their offspring from one or more years. Turnover among young members of a pack is common as they leave to search for mates and start packs of their own. Breeding members typically spend more time in the pack and act as social glue.

　　Borg and other park researchers and collaborators from UAF and the Alaska Department of Fish and Game examined data collected on 70 packs during a long-term study of wolves in Denali National Park and Preserve. They found that although breeder death preceded or coincided with 77 percent of the cases where packs were no longer found, the death of a breeding individual did not always lead to the end of a pack. In about two out of three cases where a breeder died, the pack continued.

　　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.