Journal of Comparative Physiology B

, Volume 171, Issue 5, pp 395–400

Changes in heart rate are important for thermoregulation in the varanid lizard Varanus varius

  •  F. Seebacher
  •  G. Grigg
Original Paper

DOI: 10.1007/s003600100188

Cite this article as:
Seebacher, F. & Grigg, G. J Comp Physiol B (2001) 171: 395. doi:10.1007/s003600100188


Laboratory studies and a single field study have shown that heart rate in some reptiles is faster during heating than during cooling at any given body temperature. This phenomenon, which has been shown to reflect changes in peripheral blood flow, is shown here to occur in the lizard Varanus varius (lace monitor) in the wild. On a typical clear day, lizards emerged from their shelters in the morning to warm in the sun. Following this, animals were active, moving until they again entered a shelter in the evening. During their period of activity, body temperature was 34–36 °C in all six study animals (4.0–5.6 kg), but the animals rarely shuttled between sun and shade exposure. Heart rate during the morning heating period was significantly faster than during the evening cooling period. However, the ratio of heating to cooling heart rate decreased with increasing body temperature, being close to 2 at body temperatures of 22–24 °C and decreasing to 1.2–1.3 at body temperatures of 34–36 °C. There was a significant decrease in thermal time constants with increasing heart rate during heating and cooling confirming that changes in heart rate are linked to rates of heat exchange.

Heart rate Body temperature Thermoregulation Lizards Heat transfer

Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  •  F. Seebacher
    • 1
  •  G. Grigg
    • 1
  1. 1.Department of Zoology and Entomology, The University of Queensland, Brisbane QLD 4072, Australia
  2. 2.Present address: School of Biological Sciences, A08, The University of Sydney, NSW 2006, Australia