THE ROLE OF PREDATION IN LIMITING MOOSE AT LOW-DENSITIES IN ALASKA AND YUKON AND IMPLICATIONS FOR CONSERVATION

We address 3 major questions facing wildlife managers and wildlife users of northern ecosystems: (1) Why do moose (Alces alces) often remain at low densities relative to K carrying capacity (KCC) in lightly harvested systems? (2) What is the range of potential moose harvest yields from these northern systems? and (3) What are some steps that can reduce the controversy over management of moose, wolves (Canis lupus), and bears (Ursus arctos and U. americanus)? We assessed the roles that nutrition, snow, harvest, disease, and predation played in limiting moose densities in a 9,700-km2 area in east-central Alaska during 1948-88. Our intensive study occurred during 1981-88, and we reviewed and reanalyzed historical data. We also present published and unpublished moose, wolf, and bear inventory data and moose harvest data from 35 other areas. We identified predation by wolves and bears as the major factor limiting moose at low densities in the experimental area during 1976-88. Moose irrupted simultaneously with a predator reduction program (1948-60) that included poisoning. The subsequent decline of moose ended about 1976, at which time wolves declined and survival of moose increased. During the mid-1980's and after the recent wolf reduction (1981-83), we estimated that predators annually killed 31% of the postcalving moose population, compared with 6% killed by factors other than predation and 1.5% by humans. We concluded that mortality due to predation had a substantial additive component during the low-density phase. Data from throughout Alaska and Yukon indicate that where wolves and bears were near KCC and moose were a primary prey, moose populations were within a low-density dynamic equilibrium (LDDE) (xBAR = 148, range = 45-417 moose/1,000 km2 of moose habitat). Moose usually attained elevated densities (xBAR = 663, range = 169-1,447 moose/1,000 km2) where humans held wolves and/or bears below KCC. These elevated moose populations yielded approximate sustainable harvests of 20-130 moose/1,000 km3 compared with 0-18/1,000 km2 in systems with predators near KCC. We describe several options and recommendations aimed at reducing the controversy over managing predation to elevate moose harvest. One management option, after moose reach elevated levels, is to maintain wolves at densities found in systems without predation management. Greater public participation in the development of wildlife management plans is recommended if conservationists are to unite in addressing the most serious long-term threat to moose-wolf-bear systems, i.e. the loss of habitat.