Cattle ranchers in southwestern Alberta have suspected it for a long time and now, GPS tracking equipment confirms it: wolf packs in the area are making cow meat a substantial part of their diets.

University of Alberta researchers tracked wolves to bone yards, where ranchers dispose of dead cattle, and to sites of fresh cow kills. The study was done over two grazing seasons in 2008 and 2009. The vast study area in southwestern Alberta includes private ranchland and wooded public lands bordering the Rocky Mountains.

Researchers found that during the summer months when livestock was set out to graze on public lands, cattle made up to 45 per cent of the diet for the three wolf packs in the study. This shows a seasonal switch from the wolf's usual pattern of wild prey in the non-grazing season to cattle in the grazing season.

Four wolves in three different packs were outfitted with radio collars that included a standard tracking beacon and a device that collected and saved detailed GPS location data.

When the researchers used the radio signals to locate the general area of the collared wolf, the detailed, hour-by-hour GPS data showing the wolf's movements was uploaded into a handheld device.

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. The fieldwork turned up locations where 50 cows were killed.

Researchers calculated that, during the winter months, 85 per cent of the wolves' scavenged (already dead animals) feeding events were at bone yards located on land belonging to ranchers. The researchers noted that often the bone yards were located within a few hundred metres of grazing cattle. The ease of feeding at bone yards can also attract other predators such as grizzly bears and cougars.

Lead U of A researcher, Andrea Morehouse says the most alarming element of the research is that almost 50 per cent of the wolf packs' summer diet was cattle meat. The researchers say this shows the need for management plans in the study area in order to reduce the opportunities for wolves to prey on cattle.

The research was published online March 24 in Frontiers in Ecology and Environment.