Effect of search method and age class on mark-recapture parameter estimation in a population of red-backed salamanders

Mark-recapture methods are generally considered to more accurately reflect population trends than count data, which is especially important for indicator species. Terrestrial salamanders are often used as indicators of forest ecosystem health and may be monitored through diurnal cover object searches or nocturnal activity searches. Our goal was to determine whether search method affected encounter probabilities, whether these probabilities differed between age classes, and whether the inclusion of search method in mark-recapture models affected abundance estimates. We used program MARK to analyze 3 years of red-backed salamander (Plethodon cinereus) mark-recapture data using Pollock's robust design taken from a 144 m(2) plot. Initial encounter probabilities during night searches were consistently greater than during diurnal cover object searches. As a result, inclusion of search method in models sometimes affected abundance estimates. There was no difference between adult and juvenile encounter probabilities nor were abundance estimates affected by inclusion of age class, but there was yearly variation in the juvenile abundance estimates. For these reasons, we recommend that sampling of terrestrial salamanders include nocturnal activity searches and be conducted over multiple years. Monitoring programs of other species should take into account whether the selected search method(s) may be more likely to sample different subsets of the population of interest and how this may restrict their inferences.