Jackson Hole research on Wolf diet this past Winter revealed that Wolves predation efforts focused on what was available and what was vulnerable

Research shows wolves choose different prey on feedgrounds, natural winter range.   By Cory Hatch   Wolves ate bull elk and cow moose more than other ungulates in northern Jackson Hole last winter, in contrast to the Gros Ventre drainage, where cow and calf elk were the prey of choice, researchers said. Researchers used volunteers and a combination of VHF- and GPS-tracking collars to examine two wolf packs last year and three packs this year in Buffalo Valley and northern Grand Teton National Park. Volunteers collected data on the species type, age and sex of the animals. The crews also looked at the bone marrow of the ungulates wolves killed to determine body condition. The study area is primarily inhabited by the Pacific Creek, Phantom Springs and Huckleberry wolf packs, although some of those packs have been known to range widely in winter. From January to March, field crews from the park and the U.S. Fish and Wildlife Service documented 47 wolf-kill carcasses: 26 elk (55.3 percent), 18 moose (38.3 percent) and three deer (6.4 percent). Of the documented elk kills, wolves took down 14 bulls (53.8 percent), seven cows (26.9 percent) and two calves (7.7 percent). Researchers were not able to determine the age and sex of three animals (11.5 percent). Of the moose killed, researchers documented nine cows (50 percent), four bulls (22 percent) and 3 calves (17 percent). One moose killed was an adult of unknown sex (5.6 percent), and one was an unknown sex and age (5.6 percent). Of the three deer killed, one was a doe, one an adult of unknown sex and one a yearling of unknown sex. The results are similar to 2010 results, when researchers focused on the same areas. The findings, however, contrast with earlier data that showed wolves near feedgrounds in the Gros Ventre tend to eat more elk cows and calves. The packs for the current study were selected specifically because their home ranges don't contain large numbers of wintering elk, researchers said. The reason for the discrepancy is wolves tend to focus predation efforts on what is available and what is vulnerable, said Mike Jimenez, U.S. Fish and Wildlife Service wolf recovery project leader. Jimenez cautioned the results are preliminary; researchers plan to gather more data before results are analyzed. While cow and calf elk dominate feedgrounds, on native winter range in the northern part of Jackson Hole, bull elk and moose are more abundant. The Wyoming Game and Fish Department set up a small emergency feedground in Buffalo Valley this winter, but subject wolves "didn't go into that area very much," Jimenez said. "It's what you would expect," Jimenez said. "What you start to see is there are small pockets of animals. The bulk is [bull] elk and moose." Most of the ungulates killed by the wolves were in fairly good shape based on bone marrow samples from last year and this year, Jimenez said. The samples give an indication of the animal's body condition because bone marrow is one of the last fat reserves tapped when an animal is undernourished, he said. Still, bone marrow isn't the only indication of body condition, and high-quality bone marrow doesn't mean a given ungulate is healthy. Previous studies have shown moose, especially, are contending with several challenges. "[Researchers] describe moose as being in marginal physical condition ... related to less-than-optimal habitat quality," Jimenez said. Add parasites such as the carotid artery worm to the mix, and north Jackson Hole moose are compromised, Jimenez said. March, April and May are typically the toughest months of the year for moose, and this year's deep snowpack likely has added to the challenge. "Whenever there's a heavy snowfall ... animals have trouble moving around, Jimenez said. "They're using more energy." If heavy snowfall is accompanied by a surface crust, the already compromised moose can become easier targets for wolves. "Wolves can cruise on top of that crust," Jimenez said. "You see predation rates go up. "Moose are available, and some are going to be more vulnerable than others," Jimenez continued. "Wolves ... key into those things." Elk, on the other hand, are generally "not in terrible condition," said John Stephenson, a wildlife biologist for Grand Teton National Park. This winter's heavy snowpack highlights the need for more data before making any firm conclusions, said Steve Cain, senior wildlife biologist for Grand Teton. "The distribution of elk on the landscape varies," he said. "Many, many more have gone to the feedgrounds because the snow is so deep." "This particular winter, the number of elk on the landscape within the home ranges of the packs in the study is less than what would be there on a more normal year," Cain continued. "If any one of these packs had a percentage of elk in their diet, you would expect it to be less in a winter like this." The study is interesting because wolves are a relatively new influence on the landscape, said Cain, who explained the park's portion of the study was funded through donations to the Grand Teton National Park Foundation. "We're always interested in how a major carnivore is being integrated back into the ecosystem function in the park, filling a role that has been vacant for 70 or more years," Cain said. "If a wolf doesn't have a feedground in their home range, what do they eat?"