Molecular evidence of error rates in field identification of tiger and leopard scats and observer accuracy

Scat-based diet analysis is widely used in ecological studies to infer predation patterns, trophic relationships, and carrying capacity. However, morphological similarities among sympatric carnivore scats can compromise field identification accuracy, potentially biasing management decisions and conservation outcomes. We assessed field identification accuracy for scats collected from Kanha Tiger Reserve, India, that were putatively identified as tiger Panthera tigris or leopard P. pardus . We evaluated the ability of field experts to identify scats through visual inspection, measured morphometric parameters, and compared field assignments with species identities confirmed by genetic tools. Scats of both species showed overlapping 95% confidence intervals for weight (tiger: 126.32 g, 95% CI: 88.55–164.09 g; leopard: 78.33 g, 95% CI: 60.40–96.26 g) and diameter (tiger: 35.34 mm, 95% CI: 32.11–38.57 mm; leopard: 28.42 mm, 95% CI: 14.55–42.29 mm). Terminal hooks were significantly more prevalent in leopard scats than tiger scats (57% vs. 29%; χ²=9.36, df = 1, p = 0.002), while coiling patterns occurred similarly in both species (86% vs. 94%; χ²=0.5, p = 0.471). Logistic regression identified scat diameter as the only significant predictor of species identity (β = 0.104 ± SE 0.044, p = 0.019), but morphological traits alone could not reliably distinguish scats. Field identification of scats was highly error-prone, with individual observer error rates of ∼33–60% (mean = 46%, SE = 0.01). No significant relationship existed between observer experience and identification accuracy. Our findings demonstrate that visual identification of similarly sized carnivore scats is unreliable, and any inference from such data should be interpreted cautiously. In landscapes with multiple sympatric carnivore species, we strongly recommend genetic methods for definitive species identification from scats.