Abstract
The usage of invasive tagging methods to assess lizard populations has often been criticised, due to the potential negative effects of marking, which possibly cause increased mortality or altered behaviour. The development of safe, less invasive techniques is essential for improved ecological study and conservation of lizard populations. In this study, we describe a photographic capture-recapture (CR) technique for estimating Draco dussumieri (Agamidae) populations. We used photographs of the ventral surface of the patagium to identify individuals. To establish that the naturally occurring blotches remained constant through time, we compared capture and recapture photographs of 45 pen-marked individuals after a 30 day interval. No changes in blotches were observed and individual lizards could be identified with 100% accuracy. The population density of D. dussumieri in a two hectare areca-nut plantation was estimated using the CR technique with ten sampling occasions over a ten day period. The resulting recapture histories for 24 individuals were analysed using population models in the program CAPTURE. All models indicated that nearly all individuals were captured. The estimated probability for capturing D. dussumieri on at least one occasion was 0.92 and the estimated population density was 13±1.65 lizards/ha. Our results demonstrate the potential for applying CR to population studies in gliding lizards (Draco spp.) and other species with distinctive markings.
Highlights
The ability to recognize individual animals is vital for many wildlife monitoring programmes and behavioural studies [1].marking techniques that alter an animal’s survival probability or other life-history traits violate assumptions of demographic models [2,3]
In order to examine whether the blotches on the ventral surface of the patagium remained constant through time, we photographed the patagium and pen-marked 59 individuals dorsally with unique numerical codes using a xylene-free dark-green marker pen
Twenty five individuals were captured in the first season and 34 individuals were captured in the second season
Summary
The ability to recognize individual animals is vital for many wildlife monitoring programmes and behavioural studies [1]. Draco dussumieri has natural markings on the ventral surface of its gliding membrane (patagium; Figure 1) [19] that are large enough to be photographed and which might be specific to individuals. This charismatic animal, though common throughout its range [22,23,24], has been reported only a few times after a series of publications by John between 1962 and 1971 [17,25]. Our study did not entail collection of individuals and we made all efforts to minimize discomfort to the animal by ensuring careful handling and quick release of each captured individual back onto the tree they were first observed on
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