A face in the crowd: a non-invasive and cost effective photo-identification methodology to understand the fine scale movement of eastern water dragons

Ectothermic vertebrates face many challenges of thermoregulation. Many species rely on behavioral thermoregulation and move within their landscape to maintain homeostasis. Understanding the fine-scale nature of this regulation through tracking techniques can provide a better understanding of the relationships between such species and their dynamic environments. The use of animal tracking and telemetry technology has allowed the extensive collection of such data which has enabled us to better understand the ways animals move within their landscape. However, such technologies do not come without certain costs: they are generally invasive, relatively expensive, can be too heavy for small sized animals and unreliable in certain habitats. This study provides a cost-effective and non-invasive method through photo-identification, to determine fine scale movements of individuals. With our methodology, we have been able to find that male eastern water dragons (Intellagama leuseurii) have home ranges one and a half times larger than those of females. Furthermore, we found intraspecific differences in the size of home ranges depending on the time of the day. Lastly, we found that location mostly influenced females' home ranges, but not males and discuss why this may be so. Overall, we provide valuable information regarding the ecology of the eastern water dragon, but most importantly demonstrate that non-invasive photo-identification can be successfully applied to the study of reptiles

Map of study site: Roma Street Parkland, Brisbane.

<p>Areas highlighted represent Location 1 (L1) and Location 2 (L2) within the parkland. L1 contains ornamental floral arrangements, low lying bushes, playgrounds and several disconnected water features. On the other hand, L2 primarily contains native mature trees (including a rainforest); it appears more structurally complex as it also contains a large cliff, elevated bridges, and a large man-made lake.</p

Photo-identification of lizards.

<p>Figure demonstrates how I3S Spot software was used to identify 3 different individuals (A, B and C). The ear, nose and eye of the lizard in each photograph were marked as parameters. Zooming in to photographs we marked the leading surround of the ear, which are highlighted by red ellipses characterized by 4 green dots and a central blue dot.</p

Home range size variations between sexes.

<p>Box and whisker plot showing the means, quartile ranges and medians of logged home range size (m²) for both females (F) and males (M). The box edges show the 25^th and 75^th percentile and the whiskers at the 10^th and 90^th percentile.</p