May 31, 2011
Wolves will eat beef if they have a choice in the menu.A recent paper published by the Ecological Society of America shows that wolf diets change seasonally when livestock are on the landscape.
The study, conducted by University of Alberta PhD student Andrea Morehouse and Dr. Mark Boyce, professor at the U of A department of biological sciences, says that although wild ungulates are the primary prey for wolves, livestock predation is a growing concern in areas where wolf and livestock territory overlap.
Predation on cattle in Alberta occurs mostly in the southwest corner of the province, with 37 per cent of all paid claims on livestock losses.
Predation in this corner is a year-round problem for cattle producers because wildlife habitats overlap grazing lands.
"The primary period of concern regarding livestock loss is summer and early fall, when cattle graze freely on public land, often in high densities, with little to no monitoring," the study says.
These grazing times coincide with wolf pup rearing season.
From June to October, cluster kill sites indicated that nearly half of the animals killed by wolves were cattle, with the remaining kills being mostly elk, moose and deer. About 40 per cent of the cattle killed were calves, 40 per cent were yearlings, and less than 20 per cent were adult cows or bulls.
Scat samples indicated that killed and scavenged cattle made up about 60 per cent of the wolf diet, and the other 40 per cent was wild prey.
When cattle have been moved off these areas, and these territories are in non-grazing season, wolf diets switch back to ungulates, in what Morehouse and Boyce note as prey switching.
Because scavenging at deadstock piles makes up a large part of the seasonal diet, wolves visited these sites repeatedly, and because of the location of the deadstock piles near ranch buildings, this brought the wolves into close contact with other activities such as calving.
The study used clusters of global positioning system (GPS) telemetry relocations and scat analysis to investigate wolf diets throughout the year.
Wolf diets were studied in a 3,300 square kilometre area in southwestern Alberta, where wolf-cattle conflicts are highest. This area is a narrow region of public land that represents an important corridor between a large population of wolves in Canada and one in the U.S.
The majority of seasonally-grazed cattle in this forestry area is cow-calf pairs and yearlings.
Four wolves from three packs — the Crowsnest pack, Bob Creek pack and Castle Carbondale pack — were collared with GPS radiocollars. The data off these collars provided locations of wolfs, and as a result, depending on the time spent at these locations, also indicated kill sites or scavenge sites.
The team of researchers visited 698 cluster sites, finding 181 kill sites and 32 scavenge sites. The other sites were bedding, denning and rendevous sites.
Examination of 319 scats identified 675 prey items.
The remains of 50 cattle at wolf kill sites were identified during the course of the study from the three packs, averaging at 17 head per pack per year. The GPS data allowed the team to locate cattle that otherwise may have been classified as missing at the end of the season. Because Fish and Wildlife have to confirm kills, the data allowed sites to be identified at least sooner than they may have been otherwise.
Results from the study showed higher predation numbers than what had been previously believed.
While the predator compensation program pays 100 per cent of the market value of livestock killed by wolves or bears, and 50 per cent for probable kills, there are no programs to compensate for missing animals.
The study recommends solutions such as bear-proof metal storage bins for deadstock to reduce scavenging and to prevent wolves and bears from becoming accustomed to the livestock diet and to the pattern.
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