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Ageing wolves: How Well Do They Hunt?


Rio, courtesy of the California Wolf Center

Wolves are carnivores. They are large, fast, and intelligent social animals.  They live in a family group (pack) comprised of the breeding pair (alphas), pups of the year (four to six), and occasionally a few older offspring.  They have a large home range, usually a few hundred square miles, and protect that area from invasion by other wolves.  The life history of a wolf starts with birth in April, followed by a pup phase that lasts until one year in which the animal attains 80 to 90% of its adult size, then a yearling phase that lasts through its second year.  Throughout these periods, a young wolf is learning how to behave and hunt.  A 22-month old wolf has matured and reached breeding age, however, only the alphas in a pack normally breed.  Finally, a typical wolf in the wild only lives about four to six years.1,2

They eat what they can catch. Wolves test their prey by chasing them, looking for young, weak, injured, diseased, or old animals.  Prey animals such as deer, elk, and moose in their prime, adults younger than say eight to ten years old, can usually out run or out last wolves in a chase.  Through many thousands of years, wolves and other top carnivores have contributed to the evolutionary improvement of their prey.

But what about ageing in wolves?  If prey animals degrade over time, such that they are easier to catch, then it also seems reasonable that ageing wolves would have more difficulty capturing prey.  Strangely, scientists have only recently begun to study just how age affects carnivores.  A ten-year study of wolves’ ability to hunt in Yellowstone National Park was published last year2 with some very interesting analyses.  First, the authors defined in another article what hunt means for the wolf3.  From that definition, they selected three energy intensive phases.
• Attacking:  To chase after prey animals (does not require exceptional speed or strength),
• Selecting:  To select an individual that appears to be vulnerable (requires a burst of speed to catch up), and
• Killing:  To grab, overpower, and kill a prey animal (requires strength).
The study tracked the performance of 94 known wolves (using radio collars and physical recognition).  The authors observed 469 encounters with prey and examined 694 kills (90% elk, 7% bison, 3% other).

What the authors found was wolf performance in the attack mode peaks at one year old and declines thereafter, peaks in the kill mode at two years, and peaks in the select mode at three years.  After three years, all hunting performance degrades.  There was little evidence that either increased caution from experience or wolf gender influenced declining performance.  The pattern of decline was also unaffected by the disappearance of underperforming individuals.  Finally, the researchers found the more wolves in a pack over the age of three, the lower the pack kill rate.

So to wrap up, wolves are highly social animals that live in family groups, reach maturity in a couple of years, peak early in their ability to hunt, and live relatively short lives.
Bob MacPherson, PhD, retired scientist.

1 Wolf population dynamics 2003. T. K. Fuller, L. D. Mech, & J. F. Cockrane. in Wolves: Behavior, Ecology, & Conservation, L. D. Mech, & L. Boitani, eds. University of Chicago Press, Chicago & London.
2 Predatory senescence in ageing wolves 2009. D. R. MacNulty, D. W. Smith, J. A. Vucetich, L. D. Mech, D. R. Stahler, & C. Packer. Ecology Letters 12:1347-1356.
3 A proposed ethogram of large-carnivore predatory behavior, exemplified by the wolf 2009. D. R. MacNulty, L. D. Mech, D. W. Smith, J. Mammalogy 88(3):595-605.