Population dynamics of the critically endangered golden lancehead pitviper, Bothrops insularis: stability or decline?

Murilo Guimarães,Marcio Martins,Ricardo J. Sawaya,Paul F. Doherty,Roberto Munguía-Steyer,Marco Festa-Bianchet

doi:10.1371/journal.pone.0095203

Abstract

Little is known about vital rates of snakes generally because of the difficulty in collecting data. Here we used a robust design mark-recapture model to estimate survival, behavioral effects on capture probability, temporary emigration, abundance and test the hypothesis of population decline in the golden lancehead pitviper, Bothrops insularis, an endemic and critically endangered species from southeastern Brazil. We collected data at irregular intervals over ten occasions from 2002 to 2010. Survival was slightly higher in the wet season than in the dry season. Temporal emigration was high, indicating the importance of accounting for this parameter both in the sampling design and modeling. No behavioral effects were detected on capture probability. We detected an average annual population decrease ( = 0.93, CI = 0.47–1.38) during the study period, but estimates included high uncertainty, and caution in interpretation is needed. We discuss the potential effects of the illegal removal of individuals and the implications of the vital rates obtained for the future persistence and conservation of this endemic, endangered species.

Highlights

Snake populations have been declining around the world [1,2,3], and despite many years of gathering knowledge, snakes are still intriguing vertebrates difficult to study in the field
We identified the sex and measured the snout-vent length (SVL) of each individual using a flexible tape
Most previous estimates of snake survival did not account for detection probability [41,42], a general pattern of high survival was suggested for vipers [4,43,44]

Summary

Introduction

Snake populations have been declining around the world [1,2,3], and despite many years of gathering knowledge, snakes are still intriguing vertebrates difficult to study in the field. Part of such difficulty derives from their natural history characteristics, which include elusive habits, cryptic behavior, and low densities [4,5]. Accounting for detectability improves the estimation of population rates, including abundance and dynamics, critical for managing species [17]. This, in turn, enables more effective management guidelines to be implemented in snake populations [5,13]

Methods

Results

Conclusion