Prey-to-fox isotopic enrichment of 34 S in bone collagen: Implications for paleoecological studies.

For the first time, we present direct δ34 S data for the bone collagen of a free-living predator and its naturally selected prey. Our results indicate very low or even slightly negative TEF values for sulfur. Furthermore, according to our results, the δ34 S value should not be considered a reliable indicator of trophic position in terrestrial food webs but rather, it should be used to disentangle different food webs based on different primary producers.