1919 appears to mark the beginning of the nuisance bear at Crater Lake (see Wynd 1930; Walters 1953). The subsequent “presence” of bears was probably due as much to the acclimatization of bears to humans as to an increase in population numbers suggested by Wynd (1930). While an increased food source (the garbage dumps) may have resulted in an increase in bear numbers, Herrero (1969) does not feel it was a substantial increase from pre-park levels.
A summary of minimum population-counts for Crater Lake are presented in Table 10. These counts were made primarily at garbage dumps. Although the figures were reported as minimum counts they are often interpreted as maximum population numbers. Population figures supplied to the public by naturalists range from 20 to 40 bears.
Sixteen different bears were seen during 1972 and 12 bears during 1973. These minimum counts were determined primarily from trapping and are not directly comparable with garbage dump observations. The decreasing number of bears observed at garbage dumps between: 1939 and 1969 (Table 10) does not necessarily represent an actual decrease in total bear numbers. The decreasing number of bears observed probably reflects differences in the degree of effort expended in obtaining counts and differences in the amount of garbage available to bears. Dixon (1944) indicated that high numbers of bears using the Munson Dump from the late 1930’s through 1941 was due to increases in visitor attendance and the consequent tonnage of garbage available to bears. The outbreak of World War II brought a decline in visitor attendance and a reduction in garbage. Although no figures are given by Dixon, numbers of dump bears reportedly declined during the war years. With the surge in visitation following the war, numbers of dump bears increased and then apparently slowly declined until the dumps were closed in 1971.
|Table 10. Minimum population counts of black bears in Crater Lake National Park.|
Counts made at dumps, and counts made near other developed areas are poor indicators of the park’s bear numbers. Nuisance bears are the bears most frequently observed and their numbers are easily influenced by the park’s fluctuating management practices. In addition to biases resulting from the changing management practices, counts of nuisance bears obtained near developed areas do not take into account approximately 72 percent of the park’s area which is wilderness. For these reasons an alternative method of estimating the bear population was desired.