Camera trapping photographic rate as an index of density in forest ungulates

Rovero and Marshall tested whether the rate at which animals are photographed can serve as a reliable index of their density, a crucial question because many studies use detection rates as abundance proxies. Working with forest ungulates whose densities were independently known from line transects, they found that photographic rates correlated positively with density, supporting cautious use of the index under certain conditions. However, the relationship depends on stable detectability across sites and species, a strong assumption. The study provided empirical grounding, and important caveats, for relative-abundance indices widely used when full density estimation is impractical. It is a key reference in debates over whether and when camera-trap photographic rates can substitute for rigorous density estimates.