The Thermoregulatory Behaviours and Thermal Properties of the Polymorphic Elegant Gecko (Naultinus elegans)

Abstract

Colour polymorphisms are the phenotypic differences in colours seen within populations regardless of sex, age, and seasons directly due to genetic variation. Animal colouration is important in various aspects of an animal’s life such to attract mates, prey, camouflage, establish status and thermoregulate. Ectothermic species are largely reliant on external factors to determine their thermoregulatory success. Whilst behavioural thermoregulation is the primary way ectotherms regulate their body temperature, a range of factors can alter their thermal performance. It is well known that different colours heat at different rates. Therefore, this study aims to determine the significance of colouration on thermoregulatory performance in ectothermic animals. This was done by looking at the thermal properties and thermoregulatory behaviours between the green and yellow morphs of the polymorphic elegant gecko (Naultinus elegans). Firstly, I ran experiments to investigate the thermal properties, of the gecko colours. The green coloured models had increased rates of heating and cooling in comparison to yellow-coloured models who showed a more stable relationship in response to thermal stimuli. Secondly, I observed eight elegant geckos at the Auckland Zoo, four green morphs and four yellow morphs, to assess for differences in thermoregulatory behaviours. The data showed a difference in the thermoregulatory behaviours between the morphs. The experimental data and field data supported each other. The differences in thermoregulatory behaviour and thermal properties between the green and yellow morphs show that the morphs display behaviours beneficial to the thermal properties of their colour. For the yellow morph, maintaining a stable temperature allows them to occupy more microhabitats with varying temperatures. The green coloured morphs have the capacity to utilise large temperature ranges, therefore, are found in microhabitats with varying temperatures. Risk of predation is low as the environments that provide these preferred conditions to the morphs happen to be similar to the colour of the morphs. Thus, this study suggests polymorphism in the elegant gecko is a result of differences in thermal properties in the gecko colours which influences their thermoregulatory behaviours, providing each morph population with an overall net benefit in the microhabitat they tend to occupy.