Visual encounters on line transect surveys under-detect carnivore species: Implications for assessing distribution and conservation status

PLoS One. 2019 Oct 30;14(10):e0223922. doi: 10.1371/journal.pone.0223922. eCollection 2019.

Abstract

We compared the distribution and occurrence of 15 carnivore species with data collected monthly over three years by trained native trackers using both sign surveys and an encounter-based, visual-distance method in a well-preserved region of southern Guyana (Amazon / Guiana Shield). We found that a rigorously applied sign-based method was sufficient to describe the status of most carnivore species populations, including rare species such as jaguar and bush dog. We also found that even when accumulation curves for direct visual encounter data reached an asymptote, customarily an indication that sufficient sampling has occurred to describe populations, animal occurrence and distribution were grossly underestimated relative to the results of sign data. While other researchers have also found that sign are better than encounters or camera traps for large felids, our results are important in documenting the failure of even intensive levels of effort to raise encounter rates sufficiently to enable statistical analysis, and in describing the relationship between encounter and sign data for an entire community of carnivores including felids, canids, procyonids, and mustelids.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Carnivora*
  • Conservation of Natural Resources
  • Ecosystem
  • Surveys and Questionnaires*

Grants and funding

The National Science Foundation (Grant BE/CNH 0508094) and the Gordon and Betty Moore Foundation (Grant 2054.01) provided funding for this project. The National Council of Technological and Scientific Development (CNPq-Brazil) provided a scholarship to F.G. (process 202214/2015-0) and Stanford University provided additional financial support (process 51211805202). F.G. was also supported by Grant 2017/24252-0 and 2019/00648-7 by São Paulo Research Foundation (FAPESP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.