Nonlinear effects of group size on the success of wolves hunting elk

Directly observed wolf hunts of elk in Yellowstone across several winters, recording group size and outcome, and modelled how the probability of a kill changed as the number of hunting wolves increased.

Studied in

Canis lupus, Cervus canadensis

Sample size

directly observed wolf hunts in Yellowstone over multiple winters

Hunting success rose sharply from one to about four wolves and then levelled off, with additional wolves adding little. The plateau is attributed to individuals withholding effort once enough others are engaged, since the benefit of a kill is shared regardless.

• One population, hunting one principal prey species, in winter conditions.
• Effort withheld is inferred from the shape of the success curve rather than measured for each individual.

• Counting hunts until the curve appeared

  Do more wolves make a better hunting group, and does that keep being true?

• Predation

  A hunt is a sequence — detect, approach, attack, subdue, keep — and it can fail at every stage. Where success has been measured properly, most attempts end without a kill.

• Cooperative hunting

  Several animals hunting the same prey at once is not cooperation. Cooperation means individuals taking roles that depend on each other — and that is a harder thing to show, demonstrated in far fewer species.

• Cooperative hunting

  Wolves hunting elk get better as the group grows to about four, and then stop improving. Extra wolves add little, apparently because an animal that hangs back still eats.