Recording Heart Rates Elicited by Simulated Prey and Predator Stimuli in Turtles, Lizards, and Sprague-Dawley Rats
Byron A. Campbell and Thomas McBride, Department of Psychology, Princeton University, Princeton, NJ 08544 USA
The goal of this research was to determine the nature of the autonomic and behavioral responses that occur during simulated predation and predator avoidance in western painted turtles (Chrysemys picta bellii), savanna monitors (Varanus exanthematicus), Sudan plated lizards (Gerrhosaurus major), iguanas (Iguana iguana) and Sprague-Dawley rats (Rattus norvegicus).
The results to be presented will be illustrative of the types of questions we are asking in the laboratory and their significance for psychophysiology rather than detailed descriptions of the completed research. The intent of the presentation will be to discuss the feasibility of conducting similar research in restricted field settings and the types of telemetry capabilities needed for that type of research. The research to be described employed both implanted biotelemeters and fixed electrodes.
This research program began with an extensive analysis of the cardiac responses to a wide range of neutral stimuli (neither prey nor predator) in the laboratory rat. Typical stimuli included flashing lights, white noise, pulsating tones, and a wide range of odors. With only a few exceptions all of these stimuli produced decreases in a heart rate of up to 110 beats per minute (bpm) from baselines of 350 to 500 bpm. These cardiac decelerations were interpreted as indicative of orienting responses. In some circumstances there were accompanying behavioral orienting responses such as a change in visual fixation, turning toward the sound source, sniffing, etc., but in many instances there was no observable change in behavior.
Subsequent research revealed that the same stimuli failed to elicit detectable changes in a heart rate in either turtles, savanna monitors, iguanas, or Sudan plated lizards. Other research showed that simulated predator stimuli such as the approach of the experimenter's hand or a visual stimulus that increased rapidly in size (a looming stimulus) produced either bradycardia, bradycardia followed by tachycardia, or tachycardia depending upon species and experimental conditions. These cardiac responses were sometimes accompanied by defensive responses, but in most instances there was no detectable accompanying behavioral response prior to flight.
Additional research showed that stimuli preceding the appearance of food elicited bradycardia in the rat but tachycardia in the other species. In some instances the increase in a heart rate was accompanied by behavioral orienting responses such as head turning or tongue flicking but in other instances there was no visible change in behavior prior to the capture response.
Taken together these findings suggest that biotelemetry of basic physiological data could be of great interest to behavioral psychophysiologists, behavioral biologists, and many others.
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