Bears eat moose, an interaction that forms a natural and important part of the predator-prey dynamics in various northern ecosystems. This relationship involves specific bear species, hunting circumstances, and ecological implications for both bear and moose populations.
Key Bear Species and Their Diets
Brown bears, including the North American grizzly bear, are major predators of moose across their range. While omnivores, eating a variety of foods, moose can constitute a large portion of their diet, particularly in spring and early summer. In some areas, ungulate meat, including moose, can make up a percentage of a brown bear’s annual energy intake, sometimes up to 51% of their year-round diet.
Black bears also prey on moose, though typically less than brown bears, and primarily target calves. While their diet is predominantly vegetation, moose calves can be a food source for them. In certain regions where grizzly bears are less common, black bears can become the main predator of moose calves, accounting for about 40% of calf mortality in some Alaskan areas.
Predation Strategies and Circumstances
Bears target moose under specific circumstances, making some individuals more vulnerable. Calves are highly susceptible to bear predation, particularly newborns. Brown bears frequently prey on newborn moose calves, with minimum predation rates ranging from one calf per 7-12 bear-days. Black bears also target neonatal moose, with estimated rates of one calf per 11-53 bear-days.
Adult moose are also preyed upon, although less frequently than calves, often when weakened or during specific periods. Sick or injured adults, as well as those stressed by harsh winter conditions like deep snow, can become targets. Female moose are vulnerable during and immediately following the calving period in spring. Male grizzly bears, being larger and more powerful, are noted to kill adult moose, with estimates suggesting an individual male can take 3.3-3.9 adult moose annually. Bears are primarily predators rather than scavengers when it comes to moose, killing four times more animal biomass than they scavenge in some areas.
Ecological Significance
Bear predation shapes the dynamics of the ecosystems they share. Bears contribute to maintaining healthy moose populations by removing vulnerable individuals, such as the young, old, sick, or injured. This selective pressure can help prevent the spread of disease and improve the overall fitness of the moose herd.
Bear predation influences moose distribution and behavior, as moose may avoid areas with high predator densities, particularly during calving season. The combined predation pressure from bears and wolves can keep moose densities below what their habitat could otherwise support. This predator-prey interaction is a natural regulatory mechanism that impacts the long-term balance of wildlife populations.