Volume 5, Number 48 - February 23, 2006
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Wolf population saturated
Yellowstone National Park’s wolf population isn’t expected to continue to grow because the region is saturated with wolves, according to the U.S. Fish and Wildlife Service.
The agency reported that wolf numbers in the Greater Yellowstone Area were down in 2005, with 221 wolves in 13 breeding pairs. FWS reported in its advanced rulemaking for de-listing the region’s wolf population that the decline of wolves in Yellowstone National Park occurred because:
• highly suitable habitat is saturated with wolf packs;
• conflict among packs appears to be limiting population density;
• there are fewer elk than when reintroduction took place; and
• a suspected, but as yet unconfirmed, outbreak of canine parvovirus or canine distemper.
“Additional significant growth in the Yellowstone National Park portion of the Wyoming wolf population is unlikely because suitable wolf habitat is saturated with wolf packs,” FWS reported.
“A large decline in native ungulate populations could result in an increase in conflicts with livestock and the level of wolf control,” according to FWS.
“If the wolf population continues to expand, wolves will increasingly disperse into unsuitable areas that are intensively used for livestock production,” FWS reported. “A higher percentage of wolves in those areas will become involved in conflicts with livestock, and a higher percentage of them will probably be removed to reduce future livestock damage. Human-caused mortality would have to remove 34 percent or more of the wolf population annually before population growth would cease.”
FWS’ advanced notice of proposed rule making outlines the agency’s intent to remove gray wolves in the Northern Rocky Mountains from the federal list of threatened and endangered species. The agency emphasized that unless or until Wyoming changes its state law and its plan to manage wolves upon delisting, FWS has no plans to move forward with delisting.
FWS reported, “While there are currently more than seven wolf packs outside the park because of the Endangered Species Act’s protections, it is likely that predatory animal status – if implemented at this time – would quickly reduce wolf packs outside the park to minimum levels, and based on current conditions, only 12-14 packs would exist in the state.”
FWS reported that about 26 percent of adult-sized wolves die every year in the Northern Rockies wolf population. Agency control of problem wolves and illegal killing are the two largest causes of wolf death; and combined they removed nearly 20 percent of the population annually and are responsible for 60 percent of all known wolf deaths.
Wolf mortality from agency control of problem wolves (which includes legal take by private individuals under defense of property regulations) is estimated to remove around 10 percent of adult radio-collared wolves annually.
“Overall wolf mortality has been low enough from 1987 until the present time that the wolf population in the Northern Rocky Mountains has steadily increased, and is now at least twice as numerous as needed to meet recovery levels,” FWS stated.
A level of wolf mortality as high as 50 percent is typically sustainable on an annual basis, according to FWS.
Wolf populations can rapidly recover from severe disruptions such as very high levels of human-caused mortality or disease. After severe declines, wolf populations can more than double in just two years if mortality is reduced. FWS reported that increases of nearly 100 percent per year have been documented in low-density suitable habitat.
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