Elsevier

Animal Behaviour

Volume 16, Issue 1, February 1968, Pages 129-134
Animal Behaviour

Ultrasounds in young rodents. II. Changes with age in albino rats

https://doi.org/10.1016/0003-3472(68)90123-1Get rights and content

Abstract

Pups from three litters of albino rats were monitored with an ultrasound detector while isolated under standard conditions. The experiment was planned in order to analyse quantitative and some qualitative changes with age in the ultrasonic distress calls. Systematic detections wtre made with a band-width of 5 kHz and a range of central frequencies varying from 35 to 55 kHz.

Detections within this range were low during the first days after birth, but they rose considerably with the opening of the ears (unfolding of external ears) and reached a maximum at this stage. Subsequently, the rate of calling decreased with successive days and progressively fell off to zero from day 21 onwards.

Changes in physical characteristics of the ultrasounds probably occurred with increasing age of the pups. It is likely that the distress calls stay at a constant frequency for longer periods during the days between the opening of the ears and the opening of the eyes, than during the earlier and later days.

The rate of distress calling does not seem to be related to the pups' effectiveness in eliciting maternal behaviour in adults because it is apparently lowest when the pups are most effective i.e. during the first days after birth.

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Present address: Laboratoire de Psychologie, Université de Bruxelles.

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