Stability of detectability over 17 years at a single site and other lizard detection comparisons from Guam

Journal of Herpetology
By: , and 

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Abstract

To obtain quantitative information about population dynamics from counts of animals, the per capita detectabilities of each species must remain constant over the course of monitoring. We characterized lizard detection constancy for four species over 17 yr from a single site in northern Guam, a relatively benign situation because detection was relatively easy and we were able to hold constant the site, habitat type, species, season, and sampling method. We monitored two species of diurnal terrestrial skinks (Carlia ailanpalai [Curious Skink], Emoia caeruleocauda [Pacific Bluetailed Skink]) using glueboards placed on the ground in the shade for 3 h on rainless mornings, yielding 10,286 skink captures. We additionally monitored two species of nocturnal arboreal geckos (Hemidactylus frenatus [Common House Gecko]; Lepidodactylus lugubris [Mourning Gecko]) on the basis of 15,212 sightings. We compared these count samples to a series of complete censuses we conducted from four or more total removal plots (everything removed to mineral soil) totaling 400 m2(about 1% of study site) in each of the years 1995, 1999, and 2012, providing time-stamped quantification of detectability for each species. Unfortunately, the actual population trajectories taken by the four species were masked by unexplained variation in detectability. This observation of debilitating latent variability in lizard detectability under nearly ideal conditions undercuts our trust in population estimation techniques that fail to quantify venue-specific detectability, rely on pooled detection probability estimates, or assume that modulation in predefined environmental covariates suffices for estimating detectability.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Stability of detectability over 17 years at a single site and other lizard detection comparisons from Guam
Series title Journal of Herpetology
DOI 10.1670/14-085
Volume 49
Issue 4
Year Published 2015
Language English
Publisher The Society for the Study of Amphibians and Reptiles
Contributing office(s) Fort Collins Science Center
Description 9 p.
First page 513
Last page 521
Country Guam
Online Only (Y/N) N
Additional Online Files (Y/N) N