Sampling elusive species in karst environments: design and demographic modeling considerations

Authors: B. A. Collier, D. B. Fenolio

One of the primary difficulties associated with populations endemic to cave ecosystems is estimating basic biological parameters such as abundance, survival, and recruitment. As many karst systems can be perturbed, determining estimates of demographic variables are central to evaluating whether anthropogenic or environmental influences cause variation in population distribution and trajectories. Currently, sampling design and inference methods for demographic parameters are readily available and widely applied to a range of terrestrial fauna. Our objective is to provide an overview of potential sampling designs and demographic estimation methodologies which would be amenable for use on a variety of subterranean species. We will discuss concepts associated with spatial and temporal constraints contingent on the biology of the species under study, provide examples of potential sampling designs applicable to subterranean systems, and outline estimation techniques addressing issues associated with estimation of observability, presence/absence, abundance, survival and recruitment estimation, and transience associated with temporary and permanent emigration. While general and applicable, few sampling designs or modeling applications have been applied to karst species, likely due to perceived difficulties associated with low species abundance, limited spatial and temporal distribution, and unobservable states. However, we suggest that further investigation be directed towards design and application of common estimation approaches to further our understanding of the fauna existing in subterranean ecosystems.

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