PREDATION AND MOOSE POPULATION-DYNAMICS - A CRITIQUE

The wide acceptance of predation as the major limiting and/or regulatory factor on moose (Alces alces) populations is premature because assumptions have not been addressed, alternative hypotheses have not been given similar consideration, and adequate experiments have not been conducted. I evaluated the empirical information available to assess the role of predation in the population dynamics of North American moose. Studies that estimated losses of adult moose to wolves (Canis lupus), or monitored losses by radio telemetry, indicate that wolf predation is a limiting factor with a magnitude equal to or less than other sources of mortality (particularly hunting). Three studies found that brown (Ursus arctos) and black (Ursus americanus) bears can take 50% of calves and that these losses represent the most significant mortality factor. Predation rates by wolves or bears generally do not seem to be density dependent. Experimental reduction of wolves produced increases in calf survival in 2 of 5 cases, but significant increases in density in only 1 instance. Bears have been removed in 3 instances and calf survival has been improved in each case. I reviewed 4 predator-moose hypotheses and outlined their specific predictions. Presently, empirical data are inadequate to test among them, and 2 experiments are required to do so. Moose densities should be reduced in one and bears and wolves should be removed in another; both should be followed by monitoring of changes in moose population.