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

Abstract

Rationale:The trophic enrichment factor (TEF) is a parameter reflecting the difference in isotopic ratio between a consumer's tissues and diet, used in isotopic ecology and paleoecology to track dietary habits. The TEF of sulfur is believed to be low, but was, until now, only documented in a limited number of taxa. In this study we use a subfossil accumulation of bones from a red fox (Vulpes vulpes) den to verify the TEF for sulfur in fox bone collagen. Methods: Collagen was extracted from 30 samples of subfossil bones, includingfoxes and their prey. The δ 34 S values of the bone collagen samples were measured with an elemental analyzer connected to an isotope ratio mass spectrometer. The TEF was calculated as [Δ 34 S = (mean δ 34 S in predator) -(mean δ 34 S in prey)], using taphonomic indices to estimate the mean diet, and calculated separately for different age classes of the predator. Results:We modeled 12 variants of TEF for different estimations of the diet composition and for three fox age classes (adult, subadult, and juvenile). The estimated TEF values range from −0.54 to +0.03‰ and are similar to TEFs known for other mammals. Absolute TEF values are nearly equal to or lower than the analytical error, which is ±0.4‰. Conclusions:For the first time, we present direct δ 34 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 δ 34 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.

Assessing geographic controls of hair isotopic variability in human populations: A case-study in Canada

“…δ 34 S values in human tissues reflect in part the amount of seafood consumed [44] because the oceans have a high and isotopically uniform δ 34 S transmitted to marine food chains [45]. Though results remain ambiguous, δ 34 S values are potentially influenced by trophic level [30,46,47] and internal metabolism [48]. δ 34 S baselines in food systems also display spatial patterns related to the local environmental conditions at the site of production [49] including bedrock geology [50,51], climate [52], soil properties [52], aerosol deposition [50] and fertilization practices [53,54].…”

Combined oxygen and sulphur isotope analysis—a new tool to unravel vertebrate (paleo)-ecology

“…bone collagen) with low isotopic fractionation (+ 0.5‰ ± 2.4‰, Nehlich 2015), especially when compared to the oxygen isotopic system. A recent study also measured very low sulphur isotope fractionation values between the collagen of sub-fossil red fox and that of its preys (ranging from − 0.54 to + 0.03‰, with a mean analytical error of ± 0.4; Krajcarz et al 2019). Notably, this study further allows such low sulphur isotope fractionation to apply for carnivores.…”

Isotopic insights into the early Medieval (600–1100 CE) diet in the Luistari cemetery at Eura, Finland

“…Sulfur isotopes have proven to be useful in studies on diet (e.g., Krajcarz et al 2019;Nehlich et al 2011) and as tracers of different living environments (Richards et al 2001). According to controlled feeding studies the δ 34 S values of collagen change little compared to diet (Krajcarz et al 2019;Nehlich 2015).…”