Analysing the effect of movement on local survival: a new method with an application to a spatially structured population of the arboreal gecko Gehyra variegata.

Mortality during movement between habitat patches is the most obvious cost of dispersal, but rarely it has been demonstrated empirically. An approach is presented, which uses capture-mark-recapture data of an arboreal gecko species to determine the effect of individual movement on local survival in a spatially structured population. Because capture-mark-recapture data are widely available for a range of animal species, it should be possible to extend their application to other species. The method is based on the assumption that the tendency to be a territorial animal or to be a floating animal is fixed during the study period. The advantage of our approach is that only one additional parameter has to be estimated for describing movement risks. We further tested the power of our approach to detect an association of movement and mortality with simulated capture histories. The study revealed a strong negative effect of movement on local survival. Hence, animals that moved more often between trees had a lower survival rate. Interestingly, the mean movement rate for males was significantly higher than for females, which should lead to a biased sex ratio towards females in the population. As there was an even sex ratio in the population, we discuss not mutually exclusive explanations for this finding like differences in emigration rates between sexes, differences in survival rates between sexes, or a skewed sex ratio in offspring.