Survival and abundance of Cape dwarf chameleons, Bradypodion pumilum, inhabiting a transformed, semi-urban wetland
The Cape dwarf chameleon, Bradypodion pumilum, inhabits urban areas within a critically endangered ecosystem. In this study, temporal dynamics of local demographic parameters were investigated for a population of B. pumilum inhabiting a 0.56 hectare patch of transformed habitat bordering an urban area in Noordhoek, South Africa. Robust Design (RD) capture-mark-recapture (CMR) models were used to estimate population demographics because of their ability to distinguish and account for temporary unavailability of individuals versus being captured. RD models were fit to one year of CMR data to examine adult survival and local abundance. Additionally, multi-strata (MS) models were used to analyze chameleon growth rate and size-specific survival. The results indicate the site supports a fluctuating abundance of individuals, ranging from ca. 25–91 adult chameleons. Larger chameleons showed higher 30-day and annual survival rates than smaller individuals regardless of sex (30-day range: 0.56–0.84; annual range: 9.51x10-5–0.12). Chameleons that survived to the beginning of each age class spent on average 1.1 months at 40–50 mm; 1.7 months at 50–60 mm; 2.5 months at 60–70 mm; and 6.3 months at >70 mm. Despite seasonality in the environment, there was no significant seasonal variation in chameleon survival. These findings indicate chameleon population dynamics characterized by local population fluctuations despite predominately constant, low survival; our findings suggest reproduction drives population fluctuations. Bradypodion pumilum's high fecundity and low survival should allow for their persistence in disturbed habitats assuming they are able to take advantage of suitable conditions. Alternatively, these biological traits may make B. pumilum prone to large demographic fluctuations, yielding a high risk of local extinction. This study provides temporal data on local population dynamics and survival for a potentially threatened reptile species inhabiting altered habitats.
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Document Type: Research Article
Publication date: 2013-10-01
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- The Herpetological Journal is an international scientific journal that publishes papers on the natural history of amphibians and reptiles. Experimental, observational and theoretical studies are published along with reviews and book reviews. Faunistic lists, letters and results of general surveys are not published unless they shed light on herpetological problems of wider significance.
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