Tracking animal movements using biomarkers in tail hairs: a novel approach for animal geolocating from sulfur isoscapes

Abstract

Background Current animal tracking studies are most often based on the application of external geolocators such as GPS and radio transmitters. While these technologies provide detailed movement data, they are costly to acquire and maintain, which often restricts sample sizes. Furthermore, deploying external geolocators requires physically capturing and recapturing of animals, which poses an additional welfare concern. Natural biomarkers provide an alternative, non-invasive approach for addressing a range of geolocation questions and can, because of relatively low cost, be collected from many individuals thereby broadening the scope for population-wide inference. Methods We developed a low-cost, minimally invasive method for distinguishing between local versus non-local movements of cattle using sulfur isotope ratios (δ34S) in cattle tail hair collected in the Greater Serengeti Ecosystem, Tanzania. Results We used a Generalized Additive Model to generate a predicted δ34S isoscape across the study area. This isoscape was constructed using spatial smoothers and underpinned by the positive relationship between δ34S values and lithology. We then established a strong relationship between δ34S from recent sections of cattle tail hair and the δ34S from grasses sampled in the immediate vicinity of an individual’s location, suggesting δ34S in the hair reflects the δ34S in the environment. By combining uncertainty in estimation of the isoscape, with predictions of tail hair δ34S given an animal’s position in the isoscape we estimated the anisotropic distribution of travel distances across the Serengeti ecosystem sufficient to detect movement using sulfur stable isotopes. Conclusions While the focus of our study was on cattle, this approach can be modified to understand movements in other mobile organisms where the sulfur isoscape is sufficiently heterogeneous relative to the spatial scale of animal movements and where tracking with traditional methods is difficult.

An insect isoscape of UK and Ireland

“…24,51,52 The largest δ 34 S gradient is that between land and sea with δ 34 S values in land mammals reflecting distance to the sea 53 following the "sea-spray effect", 54 which deposits marine-derived sulfate (δ 34 S $ +21‰,) 55 on land plants which may have variable, but generally much lower, δ 34 S values (+2 to +13‰). 52,54,56 Since there is negligible fractionation during plant uptake of S, the δ 34 S values of plants generally reflect those of the S-containing substrate. 56 Plants may uptake S as sulfate, sulfide or as atmospheric SO 2.…”

Dietary homogenization and spatial distributions of carbon, nitrogen, and sulfur isotope ratios in human hair in South Korea

“…Dietary intake patterns are recorded in body tissues such as hair, nail, bones, and teeth, which allow for the reconstruction of lifestyle attributes related to geographic origin and dietary habits [5][6][7]. In particular, human hair is a continually growing, readily sampled tissue that can serve as a longitudinal record of movement history [8][9][10][11]. In contrast to other body tissues, hair has no metabolic activity after being produced, and diet characteristics, region-of-origin, and recent travel history are thus stored in this tissue [12][13][14].…”

“…Thus, δ 34 S values can reflect both diet and geographic origin [19,22,23]. Factors potentially explaining differences in δ 34 S values include bedrock geochemistry [11,22], atmospheric deposition of sea-spray salts on coastal soils and vegetation [19,24], and the consumption of fish-or meat-derived proteins [2,15]. Valenzuela et al [2] demonstrated distinct geographic pattern in δ 34 S values in the USA using human hair samples, where inland values were much lower than those from coastal regions.…”

The Use of Intrinsic Markers for Studying the Migratory Movements of Bats

“…Studies which have solely used δ 34 S to map domestic livestock movements (i.e., sheep, cattle) across the landscape have been successful e.g., [ 109 , 110 ], and there is great potential to expand these techniques to investigate bat migration. Due to the distinct and uniform marine δ 34 S signature (+20.3‰) [ 99 ], many studies have used stable sulfur isotopes to differentiate between marine and terrestrial origin, e.g., [ 105 , 109 , 111 ], and this has clear application to bat migration systems.…”