Data from: American black bears perceive the risks of crossing roads

Roadways may negatively impact wildlife species through vehicular-related
mortality and spatial displacement or obstruction. Here we investigated
physiological responses, which provide insights into the animal’s
perception of its environment. We deployed GPS-collars in combination with
cardiac biologgers on American black bears (Ursus americanus; 18
bear-years) in areas with differing road densities across Minnesota, USA.
We tested whether bears exhibited acute stress responses, as defined by
significant increases in heart rate (HR), associated with road crossings.
Maximum HR between successive telemetry locations were, on average, 13 bpm
higher when bears were known to cross a road. They crossed a road, on
average, once per day. Different demographic groups (males, females with
and without cubs) responded similarly. We found stronger HR responses when
crossing high-traffic roads relative to low-traffic in half of the
bear-year combinations we sampled. Bears crossed high-traffic roads mainly
at night, but low traffic roads during daylight. Bear HRs first became
elevated when 73−183 meters away from roadways. Our findings suggest that
roadways act as an acute stressor, but the magnitude of the stress
response appears to be mild. Elevated HRs may reflect an increased
vigilance and recognition of threat when preparing to cross a road. Bears’
recognition and alertness to human-related threats is adaptive for living
in human-altered landscapes.