Foraging Behavior and Habitat Use Patterns of Brown Bears (Ursus arctos) in Relation to Human Activity and Salmon Abundance on a Coastal Alaskan Salmon Stream

• Main Author: Crupi, Anthony P.
• Format: Others
• Published: DigitalCommons@USU 2003
• Subjects: Animal Sciences
• Online Access: https://digitalcommons.usu.edu/etd/4777; https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=5812&context=etd

Over the past decade, demand for recreation has increased as part of Alaska's doubling growth in tourism. Along the Chilkoot River, near Haines, fishing and bear viewing have become increasingly popular. I investigated the ecological and behavioral interactions there between two brown bears, salmon, and humans between 2000 and 2002. My objectives were to: (1) determine if specific human activities differentially influenced bear activity and foraging behavior, (2) identify temporal and spatial habitat use patterns, (3) evaluate brown bear response to natural and human disturbances and quantify related flight distances, (4) investigate changes in bear foraging behaviors in response to prey abundance and human activity to find if bears selectively forage to maximize energy intake, and (5) assess the role of individual tolerance for human proximity in relation to specific foraging behaviors. Evidence clearly indicated that temporal and spatial brown bear activity patterns were influenced by human activity. Bears were most active and spent the longest periods of time fishing when the numbers of anglers and vehicles were below threshold levels. Adult female bears disproportionately preferred (73%) non-roaded riparian habitat, while subadults were less selective. I classified over 1000 disturbance responses and found human activity accounted for 46% of bear departures with a mean flight response distance of 97 meters. When humans were either absent or at distances greater than or equal to 100 meters from bear activity, bears captured fish at higher rates, captured 2.65 times as many fish, and caught greater proportions of live fish (71%). The greatest predictors of capture rate were the time of day when bears fished, the proximity of human activity, and the individual's tolerance level. Bear tolerance for human proximity helped explain variation in capture rates, foraging bout lengths, and total salmon captured. This suggests nutritional rewards for bears adapting to human disturbance. These analyses depict clear relationships with simple interpretation of the dynamic relationships between people, bears, and their environment. With improved understanding of the Chilkoot River's natural resources, managers can work to reduce bear-human conflicts and plan for continued growth in tourism and recreation.