Ecology

A mother bear with 2 cubs on Kamchatka.

Photo by  Igor Shpilenok.

 

Population and Distribution

Brown bears are one of the most widely distributed large carnivores in the world. The Kamchatka peninsula was once entirely populated with brown bears, and in remote protected areas is still home to the highest recorded density of brown bears on Earth. Increasing human access, through road development to expand mining and mineral exploration, is fragmenting the once continuous bear population, and Kamchatka brown bears are now becoming rare in some regions close to human settlements.   Population estimates for the entire Kamchatka peninsula range from 10,000-14,000 bears in an area about the size of California. Population counts for the region are based largely on the casual observations of hunters and forest workers and are scientifically questionable. More than a decade has passed since the last aerial survey of the region, and there is a desperate need to redefine survey methods to monitor the long term trends in the bear population. 

Physical Description

Male Kamchatka brown bears can reach a weight of 700 kilograms, and are among the largest bears in the world. Their large physical size is a result of their access to rich food sources like salmon, pine nuts and berries. Maintaining body weight is crucial to survive the long period that bears spend sleeping in their winter dens (up to 6 months on Kamchatka).

Reproduction and Life Span

Female brown bears in Kamchatka can begin to reproduce as early as 4 years of age and typically have litters of 2-3 cubs. WCS research has shown that some female bears with cubs do not approach salmon streams, to avoid risking their cubs being killed by another bear. By staying away from the salmon streams the females reduce the risk of cub mortality, but are also forced to survive on less rich food sources. Gaining enough weight to survive the winter is critical for female brown bears and their offspring. Cubs are born in the dead of winter in dens where the female is hibernating. Pregnant female bears that enter the den poorly nourished will often not be able to support their offspring, and the pregnancy will end before the birth of the cubs.   The size of male brown bears is related to their social status and access to food and mates. Female bears must be induced into estrus, which means a male bear may have to follow a female bear for weeks until she is receptive to mating. During this time the male bears must fight off other male suitors. Females can produce offspring from different males in a single litter.  

Home Range

The area that a bear requires to fulfill all of its life requirements varies depending on habitat type and food sources available. In areas very rich in salmon, WCS research has shown that bears will maintain a home range as small as 12 sq km over the entire year. In areas where salmon and other food sources are scarce, however, home ranges can be as large as 1100 sq km. Data from GPS-collared bears showed that bears made movements of up to 65 km and crossed Kamchatka's central mountain range to access different salmon runs, crossing into different hunting leases and even leaving protected areas.

Habitat

Kamchatka has some of the best brown bear habitat in the world. The highest concentrations of bears occur along streams during salmon spawning. Dense dwarf Siberian pine swales as well as expansive berry tundras can be rich feeding grounds for bears. Coastal sedge meadows and lush vegetation fed by heavy rainfalls are a bear “salad bar” when less rich food sources are available. In the fall bears in Kamchatka will usually excavate dens at higher elevations on south-facing slopes.  

Food sources

Salmon including: Pink, Sockeye, Coho, Chum, King, Cherry as well as char. Dwarf Siberian pine nuts, blue berries, crow berries, cranberries, mountain ash berries and others. Bears also feed on a wide variety of vegetation usually in the early summer. In some regions bear will hunt sea otters or be fortunate enough to find dead sea mammals like seals and even whales along the shore.  

Read about threats to Kamchatka brown bears.