A Montana State University study has confirmed what many elk hunters have espoused for years: that the simple presence of wolves can adversely impact elk populations.
Ecology professor Scott Creel and his associates concluded that wolves made elk more vigilant and skittish, affecting pregnancy and calf numbers in the elk herds–indicating that wolves impact elk populations far beyond direct predation.
Even when wolves were nearly two miles away, the elk’s vigilant behavior persisted, Creel told the Spokane Spokesman-Review.
“If you look at the observed rate that wolves are killing elk calves, there are too many calves missing,” Creel said. “We can’t account for them all through direct predation.”
Creel and fellow researchers found that as body fat drops, cow elk have difficulty staying pregnant through winter. They become emaciated, unhealthy and abort, the research concluded.
During a four-year study period, Creel and his research team collected 1,205 scat samples from cow elk. The samples were taken after March 15, when pregnant elk would be in their third trimester. The scat was tested for progesterone, a hormone needed to maintain pregnancy. In areas with high wolf-to-elk ratios, progesterone levels in the scat decreased fourfold, Creel said.
The results of the study appeared in the Proceedings of the National Academy of Sciences.
“This isn’t a new idea in ecology,” Creel said. “When a predator is in the system, it affects the system’s dynamics.”