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Wyoming Range Moose Study Continues


JACKSON - The Wyoming Game and Fish Department and the Wyoming Cooperative Fish and Wildlife Research Unit recently expanded a moose research project being conducted in the northern Wyoming Range between Jackson and Pinedale. A total of 65 moose have been captured and fitted with GPS (Global Positioning System) radio collars over the past three years to learn more about their habitat use, migration patterns, and survival.

This past winter, 28 cow moose were newly-fitted with GPS collars in an area between Cottonwood Creek on the south and the upper Hoback River on the north. Of these, 12 are wearing North Star GPS collars, which are providing real-time daily locations via satellite uplink. The other GPS collars deployed are set to fall off the animals after two years and require researchers to recover the collar before the location data can be downloaded.

This year, body condition was again estimated through ultrasonography of rump fat on each captured female. “We don’t yet know how much fat Wyoming moose need to survive winter and produce calves in the spring, but in comparison to fat levels of a declining moose population in Minnesota, moose in the Sublette herd appear to be in fairly poor condition,” said Matt Kauffman, who serves as the co-project leader, and leader of the Wyoming Cooperative Fish and Wildlife Research Unit in Laramie.

The original study area was focused on the upper Hoback Basin to get baseline data on moose movement and habitat use in an area that was proposed for natural gas exploration by Plains Exploration and Production (PXP). In late 2012, a collaboration of sportsmen, conservationists, and Wyoming government officials worked together to organize a buyout of the leases owned by PXP in Hoback Basin. The Trust for Public Land agreed to broker the $8.75 million deal with PXP, which was met in December. The buyout has allayed concerns surrounding the potential effect of natural gas exploration on moose in the PXP leasing zone, but recent interest from Stanley Energy in exploring an adjacent 44,720 acres to the south poses yet another potential threat to moose. The Bridger Teton National Forest is currently analyzing possible alternatives for the proposed development that includes South Beaver, North Horse, and Cottonwood creeks in a Supplemental Environmental Impact Statement (SEIS). The information from the collared moose will provide timely information for the U.S. Forest Service as they prepare to update the Supplemental Environmental Impact Statement regarding the 44-7 leasing zone. A decision is expected by the end of summer 2013.

“Interestingly, information from the first two year’s data is showing that some of the radio-collared moose are very localized, spending the entire year in almost the exact same location,” said Wyoming Game and Fish South Jackson Wildlife Biologist, Gary Fralick. “This would suggest that we need to have a closer look at habitat conditions in these areas. Moreover, looking at the relationship between habitat conditions, the animals’ body condition and pregnancy rates will be especially enlightening.”

Pregnancy rates for the captured females have been notably low for the past two years. Blood tests from captures showed a 69% pregnancy rate in 2012, and this winter only 48 out of 65 individuals (74%) were pregnant. Pregnancy rates for the nearby Jackson moose herd were commonly around 90% from 2005 to 2009. Low pregnancy rates are directly tied to poor body condition, which can be a function of disease, harsh winters, and/or low-quality habitat stemming from drought and over-browsing. However, the research has shown that after the collared females have given birth, the survival rate of calves has been high (>80%) relative to other populations that are limited by predation.

“The low pregnancy rate does cause some concern,” said Fralick. “But, our overall calf ratios for the Sublette moose herd have remained somewhat stable over the last five years.” This past winter’s counts showed an overall calf ratio of 39 calves: 100 cows, which nearly matches the average of 41 calves: 100 cows over the past five years.

Many of Wyoming’s moose populations have suffered marked declines over the past several decades,particularly in the western part of the state. After experiencing a sharp decline that started during the mid-1990s, the Sublette herd has stabilized over the past few years, though numbers remain below the herd population objective set by Wyoming Game and Fish Department. The Sublette moose herd is the largest in the western U.S., currently estimated at approximately 5,000 animals, spanning an area from Hoback Junction, south to LaBarge, and from Pinedale west to Afton.

While the potential for energy development in the Hoback Basin has subsided, it remains to be seen if the 44-7 leasing zone will be developed. Although moose are relatively abundant in this area, very little is known about their demography or habitat use. The moose project’s data will provide information on the interacting influences of nutritional condition, disease, and predation, which are critical but poorly understood components of demography.

“The purpose of this research is to simply characterize how moose are using this particular landscape for such things as calving, migration, winter range, etc.,” said Kauffman. “We already know from over a decade of research on Wyoming ungulates, that habitat disturbance and loss from practices such as gas development, negatively impacts local populations. We’re not so much looking at the question of ‘if’, but rather ‘how’ potential development is likely to impact moose. If development occurs, we hope this information can allow it to be done in a way that minimizes impacts to moose, and other wildlife.”

(Contact: Mark Gocke, 307-733-2383 ext. 231)



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