Change-in-ratio density estimator for feral pigs is less biased than closed mark-recapture estimates
Wildlife Research
By: L.B. Hanson, J.B. Grand, M.S. Mitchell, D.B. Jolley, B.D. Sparklin, and S.S. Ditchkoff
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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.
Suggested Citation
Hanson, L., Grand, J., Mitchell, M., Jolley, D., Sparklin, B., Ditchkoff, S., 2008, Change-in-ratio density estimator for feral pigs is less biased than closed mark-recapture estimates: Wildlife Research, v. 35, no. 7, p. 695-699, https://doi.org/10.1071/WR08076.
| 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 |