Effects of temperature on ultrasound production by infant albino rats

Abstract

The influence of temperature on production of ultrasonic distress calls by infant Wistar rats was investigated. Call rates of pups aged 2 to 18 days were recorded at ambient levels chosen to provide for a decline in body temperature (2° and 20°C), an increase in body temperature (40°C), and minimal changes in body temperature (35°C). Isolated pups were exposed to each temperature for 4 1/2 min, during which ultrasounds from 30 to 50 kHz were monitored. Low ambient temperatures consistently elicited high rates of ultrasound production, although call rate was not inversely proportional to ambient temperature. High ambient temperatures were ineffective in eliciting increased calling. Calling was infrequent at the neutral temperature, indicating that nonthermal stimuli associated with the isolation condition are relatively ineffective in eliciting ultrasound production. Decline in call rate beyond 8 days of age is apparently related to developing homeothermy which reduces the survival value of distress calls in attracting the mother.