Population abundance, size structure and sex-ratio in an insular lizard

Simone Tenan, Andreu Rotger Vallespir, José Manuel Igual, Óscar Moya, J. Andrew Royle and Giacomo Tavecchia

Ecological Modelling, 2013, vol. 267, issue C, 39-47

Abstract: Estimating population size and understanding its variation is a fundamental, yet complicated, aim of many ecological studies. We considered the problem of estimating spring and autumn population abundance, size-dependent population structure and sex-ratio of the endemic Balearic Lizard, Podarcis lilfordi from a three occasions capture-recapture study. We used a Bayesian formulation of individual covariate models to incorporate individual sex, size and trap-response. We first considered a set of simulated data with a medium-to-low probability of recapture and individual recapture heterogeneity to evaluate potential problems in model fitting and selection. Results from simulated data indicated a low performance in parameter estimation and model selection when probability of detection was low (0.15–0.30). We found a negative permanent trap response and a positive effect of size on detection probability in the spring survey but not in the autumn one. The estimated mean densities varied from about 800 to 1000lizardsha−1, a high value when comparing with mainland lizard populations. The observed increase in abundance was probably due to a drop in territorial behaviour and the immigration of females into the area sampled. As a consequence, sex-ratio changed from nearly even in June (mean posterior, 95%CRI; 0.928, 0.676–1.167) to a female-skewed population in October (0.612, 0.478–0.772).

Keywords: Population size; Data augmentation; Capture-mark-recapture; Individual covariates; Insular lizard; Sex-ratio (search for similar items in EconPapers)
Date: 2013
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Citations: View citations in EconPapers (1)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:ecomod:v:267:y:2013:i:c:p:39-47

DOI: 10.1016/j.ecolmodel.2013.07.015

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