An Automated System for Detecting and Reporting Trespassing Bears in Yosemite National Park

We developed and tested a system that alerts personnel when a radiocollared animal enters an area designated as off-limits. The remote alarm combines the monitoring capabilities of data loggers with a message transmitter that sends a voice message via 2-way radios when an animal enters a monitored area. We tested the remote alarm with food-conditioned American black bears (Ursus americanus) in Yosemite National Park by setting up 6 remote alarms in areas designated off-limits to bears (i.e., campgrounds and parking lots) and alternated nights when the message transmitters on the alarms were activated. We recorded the number of times a radiotagged bear entered an off-limits area, the number of times bear management detected a bear in areas off-limits, and the number of hazing events. Data loggers recorded 153 bear visits by 6 radiotagged bears, 59 with the alarm on and 94 with the alarm off. With the message transmitter activated, bear-managers found bears in areas off-limits 4 times more often than with the message transmitter off. Twelve hazing events occurred with the message transmitters active and 5 with them inactive. The number of bear visits/night to monitored areas was lower when message transmitters were active than when they were inactive, probably because bears entering areas off-limits were more likely to be detected and hazed with the message transmitter on. The remote alarm functioned well and aided park managers with their hazing program to reduce bear-human conflict.