Study finds elevated reproductive hormones in hunted wolves

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A new study indicates that heavily hunted wolf populations show elevated stress and reproductive hormones. Scientists say this can bring about evolutionary changes that can potentially increase wolf conflicts with humans and livestock.

Posted: Tuesday, November 18, 2014 

By David Ashby

 

A new study indicates that wolves in heavily hunted areas have elevated levels of stress and reproductive hormones. Researchers believe this can lead to large-scale evolutionary changes and an increase in conflicts with humans and livestock.
The study, which was published on Wednesday in the scientific journal Functional Ecology, analyzed hair samples from more than 140 wolves in heavily hunted regions in Northern Canada. Researchers discovered the wolves had higher levels of testosterone, progesterone and cortisol than wolves in regions with less hunting pressure.

Though the study does not give exact details of what evolutionary changes could occur over time because of these hormone changes, researchers did say it can cause major disruptions to the complex social structure and behavior of wolf packs.

One such disruption could be the higher birthrates per pack. “When social structure is disrupted, multiple litters per social group become more common, in part because dominant individuals can no longer prevent subordinates from breeding,” the study says.

Ralph Maughan, professor emeritus of political science at ISU, has studied public policy regarding wolves since the species was reintroduced in Idaho during the winters of 1995 and 1996. He says studies of the effects of heavily hunted cougar populations in Washington could reflect changes in Idaho’s wolf packs. “What happens is hunters will kill the biggest and oldest tom cats in the pack,” he says. “The younger tom cats who are not very experienced about things take over the pack and raise hell. It’s possible something similar could happen in heavily hunted wolf populations.”

Maughan says the federally protected wolf packs in Yellowstone National Park tend to be larger and more multi-generational than the heavily hunted packs in the park’s neighboring states.

The smaller pack sizes can lead to more issues with livestock. Smaller wolf packs are less likely to be able to take down large wild game like deer and elk, so livestock becomes easy prey as they are easier to find and kill.

This trend was reflected in Idaho Fish and Game’s 2012 annual report of the state’s wolves.

The report showed that the number of livestock killed had increased, despite an 11 percent decrease from the total estimated 2011 wolf population numbers.

Landowners and ranchers have already seen the impact wolves have made on the state’s livestock industry. According to the Department of Agriculture, wolves are believed or confirmed to have killed 78 cattle and 565 sheep in 2013. “Smaller wolf packs need to kill more often because their kills are often taken by scavengers, like coyotes, magpies and ravens,” he said. “A larger wolf pack will most likely consume their food on the spot, so proportionally, they don’t have to kill as often.”

The study was published a day before the announcement that four environmental groups have filed a lawsuit to prevent a wolf and coyote hunting derby from extending onto public BLM lands in central Idaho.

The purpose of the derby is to thin out the state’s wolf population. But if heavily hunted wolves have elevated reproductive hormones, as the new study suggests, what effect will large-skill killing of wolves have on livestock and the overall wolf population in the long term. “Hunting could increase the fertility rate,” Maughan says. “But if the social structure is disrupted, it could also mean the pups won’t even survive.”

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