Rat 22kHz ultrasonic vocalizations as alarm cries

Rats incorporate circa 22 kHz ultrasonic alarm cries into their defense pattern in response to a predator threat. These calls are dependent on conspecific presence, show gender differences, and tend to be emitted from a place of relative safety. Rats emit sonic defensive threat vocalizations when approached by a potential threat. These are emitted regardless of conspecific presence, and increase as a function of threat proximity, eventually culminating in defensive attack at close distances. Ample data from field studies suggest a similar division of vocalizations into alarm or warning cries, and defensive threat vocalizations, although both are often subsumed under the rubric of alarm cries. A clear distinction between these types of calls is necessary for proper analysis of the evolutionary mechanisms responsible for the development and maintenance of each of them. Furthermore, the integration of data from field studies and laboratory experiments may prove useful in evaluation of the relationship between each type of cry and emotional (fear or anxiety-like) states in mammals. (c) 2006 Elsevier B.V. All rights reserved.