Ageing wolves 'lose their bite'

By Jody Bourton
Earth News reporter

Living up to its grey name, the grey wolf

Old wolves lose their bite, say researchers who have found that getting old affects wolves' ability to hunt and moderates their impact on prey.

The discovery helps answer a tantalising question: does getting old impact the athletic abilities of animals just as it does people?

While it might seem obvious that it would, many eminent biologists and researchers have assumed otherwise.

They have argued that most animals tend to die before age wearies them.

Researchers examined how aging affects the ability of wild wolves (Canis lupus) aged one to eight years old to predate elk (Cervus elaphus) in the grasslands of the Northern Range part of Yellowstone National Park, in the northwest US.

Many eminent biologists have argued that aging rarely occurs in nature, because animals do not live long enough to exhibit its effects Dr Daniel MacNulty Michigan Technological University, US

In particular, they measured how age influenced the ability of the wolves to execute three hunting tasks: attacking, selecting, and killing.

The wolves' predatory performance declined with age. Also, a greater number of old wolves reduced the number of elk killed.

The study is published in the journal Ecology Letters.

Wolves in the wild typically live up to eight years old. In this study, they were considered to be growing old after three years.

Long in the tooth

"Although the effects of aging on physical performance in humans are well-known, the effects of aging in wild animal populations have been controversial," says Dr Daniel MacNulty of the Michigan Technological University in Houghton, US.

"Many eminent biologists have argued that ageing rarely occurs in nature, because animals do not live long enough to exhibit its effects."

"My study refutes this notion as well as demonstrates that aging may have important ecological consequences in terms of how a wild population uses its environment," he says.

"Old" adversaries, the wolf and the elk

Dr MacNulty says his team's study is the first to show how the age structure of a wild and unexploited predator population fluctuates, and how it moderates the impact of predators on prey.

The findings suggest age is an important, though overlooked factor, in the dynamics of animal communities.

"Ecologists typically assume that the age structures of wild populations are stable."

"This is analogous to the impact of workforce ageing on the economic output of many industrialised nations," Dr MacNulty says.

"The ageing of individual wolves appears to limit the predatory output of the wolf population."

He now hopes to examine how age can impact predator prey dynamics over time.

He also would like to investigate how disease, harvest and other factors may affect the ages of surviving wolves and indirectly impact wolf-elk dynamics.