WY Wolf Population Drops 18%
by Cat Urbigkit, Pinedale Online!
April 21, 2019
Despite the deaths of 177 wolves in Wyoming in 2018, the state¡¯s wolf population tallies at least 286 (an 18% drop from a year ago), and agencies spent at least $1.5 million on wolf management and monitoring.
Wyoming is required to maintain at least 150 wolves and 15 breeding pairs in order to comply with federal delisting standards. More specifically, under a deal negotiated between the U.S. Fish & Wildlife Service (FWS) and the State of Wyoming, state officials are responsible for maintaining at least 100 wolves and 10 breeding pairs within the state¡¯s jurisdiction, while Yellowstone National Park and the Wind River Indian Reservation are expected to contribute the remaining 50 wolves and 5 breeding pairs to meet the 150 wolves/15 breeding pair requirement.
The Wyoming Game & Fish Department¡¯s recently released annual report on wolf monitoring breaks down the existing population in this way:
Wyoming Wolves: 196 wolves/13 breeding pairs
Yellowstone National Park: 80 wolves/7 breeding pairs
Wind River Indian Reservation: 10 wolves/no breeding pairs
WG&F is responsible for managing wolves in northwestern Wyoming¡¯s wolf trophy game area, while in the remainder of the state, wolves are treated as predators and can be killed at any time.
WG&F had hoped that the 2018 wolf hunting season in the trophy zone would result in a reduction of the population to 160 wolves, but the result was that the wolf population within that zone dropped even more than anticipated, to 152 wolves in that zone, and 11 breeding pairs. Still, for the 17th consecutive year, Wyoming has exceeded the numerical, distribution, and temporal delisting criteria established by FWS. Wyoming¡¯s wolf population had an average of 13% growth despite 34% human-caused mortality from 2000-2018, according to WG&F.
There are currently 90 wolves in 31 packs wearing radio-collars in Wyoming, according to WG&F.
The report noted decreases in the number of wolves, wolf packs, breeding pairs, and average pack size, "primarily through human-caused mortality, but natural processes driven by density-dependent mechanisms also contributed to these reductions.
"Density-dependent mechanisms are factors that increase mortality and/or reduce pup recruitment when wildlife populations are at high density, causing a resultant limitation or reduction of population growth," according to the report. Evidence for density-dependent limitations of the wolf population include increasing disease prevalence, reduced reproduction and pup recruitment, and increased intraspecific aggression between wolf packs (i.e., wolves killing other wolves.
"For example, intraspecific aggression increased as wolf density increased in the northern range wolf population in Yellowstone National Park, contributing to reduced population growth at high density/ Similarly, documentation of much higher intraspecific aggression between wolves in WYO in 2018 suggests density-dependence was a factor influencing wolf population growth.
"Reproduction and recruitment of pups was markedly low in 2018, providing further evidence of density-dependent factors within the WYO wolf population."
There were ¡Ý80 wolves in ¡Ý9 packs, including 7 breeding pairs, living primarily in Yellowstone National Park at the end of 2018 (Figure 8, Table 3). Overall, wolf numbers fluctuated little from 2009 to 2017 (83-108 wolves) but dropped slightly in 2018, particularly in the interior of Yellowstone after the Snake River pack shifted into WYO
This is the first year since 1995 there was no intraspecific-caused mortality in Yellowstone National Park, which is usually the leading cause of natural mortality in the park.
To read the entire annual report, click on the link below.