The Social behavior of brown bears at McNeil River, Alaska

Egbert, Allan

Adjacent to/nearby KATM. (Adapted from author's abstract.) The social behavior of brown bears was studied during summer 1972 and 1973 as bears fished for salmon at McNeil River. Objectives of the study were to determine behavioral characteristics of bears in relation to sex and age, changes in social behavior over a 40-day-long fishing season, and social and environmental parameters correlated with the occurrence of behavior, as well as to test the hypothesis that brown bears modify social behavior in a feeding aggregation to exploit a resource limited in time and space. Over one-half of the agonistic interactions consisted of passive deferrals. Encounters that included elements of overt threat were jawing, sparring, charges, and fighting. Jawing was the most prevalent agonistic encounter and generally occurred between individuals of the same sex and age class. Females with young were most intolerant. Adult males participated in few encounters that involved overt threat since most bears avoided them. Single adult and adolescent females were neither particularly aggressive nor especially tolerant. Adolescent males adjusted quickly to McNeil Falls and as a group were unaggressive. Relationships between bears of different classes were mostly stable; adult males were dominant, followed in order by females with young, single adult females, adolescents, and subadults. Nonagonistic encounters occurred only when salmon were exceptionally abundant and usually involved adolescent and subadult bears. Behavioral changes over time included a decline in the frequency of running deferrals, a decline in deferrals in total, and a decline in the frequency of charges. Changes in encounter intensity over time had no detectable effect on fishing success. Salmon abundance, however, resulted in a further reduction of agonistic encounter intensity and an increase in nonagonistic encounters.