ESR 21:65-76 (2013)  -  DOI:

Population viability analysis of Critically Endangered white-rumped vultures Gyps bengalensis

Nabin Baral1,*, Christopher Nagy2, Benjamin J. Crain3, Ramji Gautam4

1Department of Forest Resources and Environmental Conservation, Virginia Tech, Blacksburg, Virginia 24061, USA
2Division of Vertebrate Zoology, American Museum of Natural History, Central Park West, New York, New York 10024, USA
3Department of Biology, University of Puerto Rico-Rio Piedras, San Juan, Puerto Rico 00936
4Department of Zoology, Prithvi Narayan Multiple Campus, Tribhuvan University, Pokhara, Nepal

ABSTRACT: More than a decade has passed since the catastrophic population decline in Gyps species was reported from South Asia, but much uncertainty remains about quantifying their short-term extinction risk. To estimate the future extinction risk of the white-rumped vulture Gyps bengalensis in Nepal, we conducted counts at 7 nesting colonies between 2002 and 2012. We compared 3 methods of estimating abundance based on count data and calculated mean population growth rates and cumulative probabilities of extinction given the abundance estimates from each method. The first 2 methods of abundance estimation were traditional indices: mean and maximum values of all counts. The third method was a mixture modeling approach that corrected raw counts by a detection parameter. The results of the traditional indices were characterized by high uncertainty levels as reflected in the wide confidence intervals, which limited their capacity to make predictions about the fate of the populations with any confidence. The mixture modeling method provided more reliable results; there was a 51% probability of populations facing quasi-extinction (i.e. ≤20 vultures) in 13 yr and a 99% probability of quasi-extinction in 18 yr. Because the mixture modeling method provided more precise predictions while requiring minimal additional effort, population biologists using count data are encouraged to employ such model-based estimators. The white-rumped vulture populations in Rampur are in danger of disappearing within 2 decades, so conservation efforts should be expedited to prevent the loss of this species.

KEY WORDS: Asian vulture crisis · Extinction probability · Nepal · Population ecology · Rampur Valley · Vulture conservation

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Cite this article as: Baral N, Nagy C, Crain BJ, Gautam R (2013) Population viability analysis of Critically Endangered white-rumped vultures Gyps bengalensis. Endang Species Res 21:65-76.

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