The small number of giant pandas (Ailuropoda melanoleuca) in the world makes this the only species of bear classified as globally endangered on the IUCN red list. The latest rangewide population estimate was derived from scats (feces) found along transects throughout the geographic range of the species. Scats were differentiated into ∼1,600 individuals based on their geographical separation and the size of bamboo stem fragments contained within (reflective of bite-sizes). Recently, a team of researchers (Zhan et al. 2006) conducted genetic analysis of scats in a Chinese Nature Reserve (Wanglang). Their estimate of giant panda numbers there was double that obtained using the bite-size technique. Taking this to be representative of the entire range, they speculated that there could be 3,000 pandas in the wild. Many in the international conservation community heralded this as evidence that panda conservation is working well. Moreover, if the revised rangewide estimate is accepted as true, it could mandate the downlisting of pandas on the red list. We believe that such conclusions are unwarranted, or at least premature. First, the DNA-based estimate in the reserve may have been inflated by lack of geographic closure (which seems probable) and genotyping errors (which we found evidence of). Second, it was inappropriate to extrapolate results from this single point to the entire range of the species. The bite-size technique may substantially underestimate panda numbers in dense populations, such as in Wanglang Nature Reserve, where many nearby individuals likely have similar bite characteristics, whereas the technique may be more accurate in differentiating individuals in more sparsely populated areas. Although molecular-based population estimation is more rigorous than the bite-size method, too much uncertainty exists in the revised estimates to surmise either current population size or trend. We recommend (1) quantification of genotyping error rates for panda feces, (2) comparison of population estimates using bite-sizes and DNA derived from the same, short-term collection of scats, and (3) incorporation of both techniques in the next rangewide population estimate.
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Vol. 19 • No. 2