It takes wolves a year or two to learn how to hunt, but their ferociousness doesn't last long.
According to a new study, most wolves lose their prowess by age 3, just halfway through their lives. After that, they have to rely on younger members of the pack to catch the majority of their meals.
The discovery adds to growing evidence that aging affects animals much like it affects people. The findings might also change the way scientists think about the health of both wolf packs and the elk they prey on.
"How many times a day is there a scene on the Discovery Channel of a large predator taking down a prey animal?" said Dan MacNulty, an animal ecologist at the University of Minnesota, Twin Cities, and Michigan Technological University in Houghton.
"It fosters this image that predators are indestructible, they have no flaws, and they can keep doing that activity throughout their lives," he said. "But the fact is that active predation is extremely demanding physically, and wolves can only maintain their peak physical performance for a short period of time."
For this study, MacNulty followed 94 radio-collared wolves in Yellowstone National Park for between one and eight years.
Twice a year, for a month at a time, MacNulty and his colleagues followed wolf packs from on the ground and in the air. The researchers observed the wolves hunting for elk and measured how successful each animal was at rushing the herd, singling out an individual elk, and chasing it down.
Wolves are notoriously difficult to observe and follow in most places. This was the first time scientists have been able to measure how successful individual wolves were at hunting, year after year.
The study revealed that wolves reach their hunting peak at age 2 or 3, even though the animals live for an average of five or six years and sometimes reach age 10 or even older.
Packs with a larger proportion of older wolves killed fewer elk than did more youthful packs. Scientists have long assumed that one adult wolf would be as dangerous as the next.
"The take-home message is that an adult wolf is only maximally lethal for about 25 percent of its adult life span," said MacNulty, whose study appeared in the journal Ecology Letters. "Carnivores simply aren't as ferocious as we think they are."
Considering differences among individual wolves can add nuance to the way scientists think about an entire wolf pack and its ability to affect the ecosystem, said John Fryxell, an ecologist at the University of Guelph in Ontario. Given what we know about aging in general, he added, the findings aren't totally surprising.
"Would you be surprised if an 80-year-old didn't win a marathon and wouldn't be the most likely survivor in a plane crash?" Fryxell asked. "It's exactly what you'd expect, but the fact is, people have not necessarily looked for it (in wolves)."