When Mexican gray wolves prey upon cattle in the southwest, they do more than just bovine harm — they become public enemy Number One to the area livestock growers. Typically, the numbers of cattle losses to Mexican gray wolves are inflated by ranchers, and down-played by wolf advocates. The truth lies somewhere in the murky middle. And so a team of researchers delved into that murky middle and studied the scats of Mexican wolves during two summers (2005 and 2006) to piece back together what the animals were actually dining upon.{1}
The team, led by Jerod Merkle, picked up scats along roads and hiking trails in the New Mexico and Arizona reintroduction area. They also followed cues from radio-collared wolves and sought out dens and rendezvous sites, where they collected even more scats. All in all, they picked up 165 scats from den sites, 109 from roads, 17 on trails and 7 at rendezvous sites (6 were gathered from other places) for a grand total of 304 poop samples. Using a previously established method for determining the mass of prey from the hairs and bones present in the fecal matter, they parsed apart what each wolf had consumed. The team tracked the samples by pack territory, and linked pack territories to the region’s predominant grazing practices: seasonal grazing, or year-round grazing. (For background on the Blue Range Wolf Reintroduction Area, see my previous posts here, here and here which both describe the wolf program in the context of the active federal lands grazing practices.)
In their overall dietary analysis, they found that 80.3 percent of the Mexican wolves’ diet was elk, 16.8 percent was cattle; deer, squirrels and rabbits comprised less than 1 percent each, and rodents made up 2 percent. This fell largely in line with a previous dietary study by Reed et al. in 2006, but it’s important to note that one pack in particular skewed the cattle numbers upward. In 2005, the researchers say that the Luna pack consumed52.7 percent of their diet as cattle and 45.9 percent as elk. The following year, the pack ate 24.1 percent of their diet as cattle, and 75.1 percent as elk. By comparison, in 2005 the Saddle pack consumed less than 4.3 percent of their diet as cattle, and 94.5 percent as elk while the Rim pack, in 2006, ate no cattle and 96 percent elk.
Next, they attempted to get a picture of the diet of packs living in areas that were managed either under year-round grazing or seasonal grazing of domestic livestock. For this part, they only included wolf packs that were represented by more than 15 scat samples. What they found was that wolves with territories that comprised land that was grazed year-round were more likely to have a higher proportion of their diet made up of cattle versus wolves that lived on land where cattle were grazed seasonally. The researchers found that those packs that resided in areas where grazing was year-round were much more likely to consume more cattle. (But again, this result was largely driven by one pack, the Luna pack.)
Granted, their study only covered two seasons, and only three to four packs were used for each season’s analysis (Blue Stem, Saddle and Luna in 2005, and San Mateo, Rim, Saddle and Luna packs in 2006), but the implications for cattle husbandry practices that are compatible with Mexican gray wolf recovery are broad. Because both seasonal and year-round grazing practices are common in the Blue Range recovery, areas where seasonal grazing is practiced may be relatively less prone to cattle losses by wolves. (The study did not parse apart calf versus adult cow in the scat remains; though many other sources indicate that it is newborn calves which take the brunt of predation by the areas predators: coyotes, black bears, cougars and even feral dogs.)
A longer term study of pack diets would be useful for helping to determine the best management practices for cattle in the area, in order to minimize cattle-wolf conflicts and preserve more wolves on the landscape with fewer losses to livestock operators.
NOTES:
{1} Merkle, Jerod et al. 2009. Summer diet of Mexican gray wolf (Canis lupus baileyi). The Southwestern Naturalist. 54(4): 480-485.
2 thoughts on “New dietary study on Mexican wolves”
cynthia lee wolf
Hey Girl,
Thanks for posting this! Still here on the Gila and still working for wildlife and working rural communties. Hope you are well!
DeLene
How is it going? I’ve been reading about the Mexican wolf in the media… seems like a low point in the program right now. What kind of work are you doing?