(Edmonton) In a two-year study that required tracking radio-collared wolves, University of Alberta graduate student Andrea Morehouse confirmed something ranchers had long suspected: their cattle had become a mainstay in the diet of local wolf packs.
"In southwestern Alberta during the summer, when ranchers let their cattle graze on public land-the home territory for local wolf packs-cows became 45 per cent of the summer diet for three wolf packs," said Morehouse. The researchers say summer grazing on public land coincides with the arrival of newborn wolf pups, which Morehouse adds puts pressure on wolf packs to bring down large prey.
Morehouse says that in the winter the wolves found easy pickings in cattle boneyards, the disposal sites on ranches where cattle killed by injury or sickness are disposed of. "Often the boneyards were located within a few hundred metres of grazing cattle," said Morehouse. "They became a magnet for wolves, especially in the winter months, when we calculated that 85 per cent of the wolf scavenged-feeding events took place at cattle boneyards."
To perform the study Morehouse and her research team had radio collars on four wolves in three different packs that operated over vast territories in southwestern Alberta. The collars sent out tracking beacons and housed another device that recorded and saved detailed GPS location data.
"We used radio signals to find the general area where the wolves were moving about and when we got close, we used a handheld device to upload a week's worth of hour-by-hour tracking information," said Morehouse. On open terrain the data uploads could be made from as far away as five kilometers from the wolves, but the researchers were not always that lucky.
On one field trip Morehouse remembers a long walk through a densely wooded area to get an upload of the wolf's movements. "We got quite a surprise when we plotted our GPS location on a map and compared it with the spot where the wolves had gathered," said Morehouse. "The trees and vegetation were so thick we didn't realize we were just 70 metres from the wolf pack."
The researchers looked for GPS clusters, the locations on the map where the wolves spent a lot of time, and went to a total 698 sites where the wolves had gathered. They turned up locations where 50 cows were killed.
Morehouse was the lead researcher on the project. She says the combined effects of summer grazing in the wolf packs' territories and the strong attraction of boneyards for all predatory animals shows a need for change.
"Our work shows the need for new management plans in the study area in order to reduce the opportunities for wolves to prey on cattle," said Morehouse.
The research was published online March 24 in Frontiers in Ecology and Environment.