RED SQUIRRELS, TAMIASCIURUS-HUDSONICUS, PRODUCE PREDATOR-CLASS SPECIFIC ALARM CALLS

Red squirrels, can produce alarm calls when they detect a potential pr edator. Observations of natural interactions between red squirrels and large birds, and predator-presentation experiments in the field, show ed that red squirrels produce acoustically different alarm calls in re sponse to aerial danger (live birds and a model hawk flown towards the m) versus danger approaching from the ground (dogs and humans). The al arm call produced in response to aerial danger is acoustically converg ent on the 'seet' alarm call produced by many species of passerine bir ds in response to raptors. The squirrels' 'seet' alarm is a short, low -amplitude, high-frequency call. These characteristics make the call d ifficult to localize, and is in a frequency range that is poorly perce ived by raptors. Red squirrels produce much louder, wide-bandwidth bar k calls in response to terrestrial danger. This is the first demonstra tion of predator-class specific alarm calls of red squirrels. (C) 1998 The Association for the Study of Animal Behaviour.