Research and Management of Black Bears in Crater Lake National Park, Oregon, 1974

 POPULATION CHARACTERISTICS

Seasonal Activity

Crater Lake bears are normally active during five to seven and one-half months each year depending on weather and elevation. Records listing the first and last dates when bears or bear tracks were seen each year are presented in Table 9.

There is some indication that, in spite of deep snow, the presence of garbage dumps allowed individual bears to remain active in excess of eight months during some years. Prior to dump closures (1971), the first bear or bear sign woo usually observed by early May, with some bears reported active as late as January. Chief Park Naturalist Bruce, While discussing pre-dump closure bear activity reported “…Old hands indicate that there is often, if not usually, a bear or so that prowls Munson Valley and the headquarters area through the winter (Bruce 1967). The two years following dump closures bear sign was not observed until late May and the last bear track seen during 1973 was on 31 October. Depths of snow on the ground at dates of first bear or bear track sightings ranged from 24 to 163 inches prior to dump closures, was 108 inches in 1972, and only 18 inches in 1973.

Table 9. Dates when first and last bear or bear sign were observed at Crater Lake National Park.*

Jonkel and Cowan (1971) reported that the Big Creek drainage in Montana has two basic types of black bear habitat. One type is used by bears year round while the other provides supplementary food and cover from mid-July through autumn. It is possible that a similar situation exists at Crater Lake. Within the Canadian and Hudsonian Life Zones snowfall generally limits food availability to June through October. Bears summering in these life zones either move seasonally to and from lower elevations or experience an active season up to two and one-half months shorter than bears occupying ranges within the Transition Zone. Bears are generally active from about May to mid-November in the Transition Zone. Since no bears were radio located after mid-October during 1973 it is unknown whether bears that summered at high elevations denned there also. If the Canadian and Hudsonian Zones are used only seasonally the presence of dumps probably increased the park’s carrying capacity to a limited degree by providing additional year round habitat for a few bears.