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Change-in-ratio density estimator for feral pigs is less biased than closed mark-recapture estimates

Wildlife Research

By:
, , , , , and
DOI: 10.1071/WR08076

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Abstract

Closed-population capture-mark-recapture (CMR) methods can produce biased density estimates for species with low or heterogeneous detection probabilities. In an attempt to address such biases, we developed a density-estimation method based on the change in ratio (CIR) of survival between two populations where survival, calculated using an open-population CMR model, is known to differ. We used our method to estimate density for a feral pig (Sus scrofa) population on Fort Benning, Georgia, USA. To assess its validity, we compared it to an estimate of the minimum density of pigs known to be alive and two estimates based on closed-population CMR models. Comparison of the density estimates revealed that the CIR estimator produced a density estimate with low precision that was reasonable with respect to minimum known density. By contrast, density point estimates using the closed-population CMR models were less than the minimum known density, consistent with biases created by low and heterogeneous capture probabilities for species like feral pigs that may occur in low density or are difficult to capture. Our CIR density estimator may be useful for tracking broad-scale, long-term changes in species, such as large cats, for which closed CMR models are unlikely to work. ?? CSIRO 2008.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Change-in-ratio density estimator for feral pigs is less biased than closed mark-recapture estimates
Series title:
Wildlife Research
DOI:
10.1071/WR08076
Volume
35
Issue:
7
Year Published:
2008
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Wildlife Research
First page:
695
Last page:
699
Number of Pages:
5