David Munoz | USGS Science

USGS2016

Spatial capture-recapture: a promising method for analyzing data collected using artificial cover objects

Spatial capture–recapture (SCR) is a relatively recent development in ecological statistics that provides a spatial context for estimating abundance and space use patterns, and improves inference about absolute population density. SCR has been applied to individual encounter data collected noninvasively using methods such as camera traps, hair snares, and scat surveys. Despite the widespread use of capture-based surveys to monitor amphibians and reptiles, there are few applications of SCR in the herpetological literature. We demonstrate the utility of the application of SCR for studies of reptiles and amphibians by analyzing capture–recapture data from Red-Backed Salamanders, Plethodon cinereus , collected using artificial cover boards. Using SCR to analyze spatial encounter histories of marked individuals, we found evidence that density differed little among four sites within the same forest (on average, 1.59 salamanders/m 2 ) and that salamander detection probability peaked in early October (Julian day 278) reflecting expected surface activity patterns of the species. The spatial scale of detectability, a measure of space use, indicates that the home range size for this population of Red-Backed Salamanders in autumn was 16.89 m 2 . Surveying reptiles and amphibians using artificial cover boards regularly generates spatial encounter history data of known individuals, which can readily be analyzed using SCR methods, providing estimates of absolute density and inference about the spatial scale of habitat use.

New York↗

USGS2015

Book review: Biology and conservation of North American tortoises

The charismatic North American tortoises hold a special place in our culture and natural history. Despite the perseverance of these tortoises over millions of years, biologists now question their ability to persist into the future. In light of documented declines, habitat loss, and numerous threats to tortoise populations, the editors gathered a diverse group of researchers to review what we have learned about this group after decades of study, to summarize gaps in the literature, and to reflect on how we may use the current state of knowledge to conserve these fascinating species. Initially intended as a focused review of the two most well-studied species in the genus Gopherus , G. agassizii (Mohave Desert Tortoise) and G. polyphemus (Gopher Tortoise), the book developed into a comprehensive treatment of the entire genus. The editors offer the work as a resource to professional biologists and agencies working with North American tortoises as well as a teaching aid, hobbyist’s reference, and casual read for nature-lovers—although we presume that the former group is more likely to benefit than the latter. Although the book’s size appears modest, the content delivers an in-depth look at the five recognized tortoise species. Review info: Biology and Conservation of North American Tortoises. Edited by David C. Rostal, Earl D. McCoy, and Henry R. Mushinsky, 2014. ISBN 978-1421413778, 190 pp.

Herpetological Review↗