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."