Orientation Preference and Behavioural Thermoregulatory Coordination in Pogona vitticeps.

Abstract

Regulating body temperature is a critical function for vertebrates and many invertebrates. Vertebrates that rely on ambient temperature as a heat source (ectotherms) make use of multiple voluntary and involuntary behaviours to thermoregulate, including body orientation. The purpose of this work was to examine orientation behaviour in bearded dragons (Pogona vitticeps) as well as possible coordination between thermoregulatory responses. Both adult and two week old neonatal bearded dragons were placed in a thermal gradient and left to thermoregulate behaviourally in order to observe the presence of a thermoregulatory orientation preference. Since a thermal orientation bias could manifest from a preference for favoring rostral versus caudal traits, animals were subsequently subjected to a separate experiment, in which either heat exchange across the tail or respiratory heat exchange from gaping was inhibited. Changes in thermoregulatory behaviour were then observed in the manipulated bearded dragons in order to assess the potential contributors to thermal preferences as well as isolate potential coordination between behaviours. Both adult and two week old neonatal dragons displayed a non-random orientation preference for facing a heat source that strengthened with time exposed to a thermal gradient, supporting this behaviour as a thermoregulatory response. Bearded dragons also exhibited changes in orientation preference and gaping behaviour when the tail was insulated and when gaping was inhibited, but no changes to selected ambient temperature, indicating that the changes to gaping and orientation behaviours are compensatory responses that support the presence of coordination between thermoregulatory behaviours.