Using sulfur stable isotope ratios (δ34S) for animal geolocation: Estimating the delay mechanisms between diet ingestion and isotope incorporation in tail hair

Abstract

Rationale: Metabolism and diet quality play an important role in determining delay mechanisms between an animal ingesting an element and depositing the associated isotope signal in tissue. While many isotope mixing models assume instantaneous reflection of diet in an animal– tissue, this is rarely the case. Here we use data from wildebeest to measure the lag time between ingestion of 34S and its detection in tail hair. Methods: We use time-lagged regression analysis of δ34S data from GPS-collared blue wildebeest from the Serengeti ecosystem in combination with δ34S isoscape data to estimate the lag time between an animal ingesting and depositing 34S in tail hair. Results: The best fitting regression model of δ34S in tail hair and an individual– position on the δ34S isoscape is generated assuming an average time delay of 78 days between ingestion and detection in tail hair. This suggests that sulfur may undergo multiple metabolic transitions before being deposited in tissue. Conclusion: Our findings help to unravel the underlying complexities associated with sulfur metabolism and are broadly consistent with results from other species. These findings will help to inform research aiming to apply the variation of δ34S in inert biological material for geolocation or understanding dietary changes, especially for fast moving migratory ungulates such as wildebeest.