Trace Elements in Claw Keratin as Temporally Explicit Indicators of Geographic Origin in Terrestrial Mammals

Biogeochemical markers in ecology are useful for indicating geographic origin and movement patterns of species on various temporal and spatial scales. By assessing these markers in a tissue that is chemically inert once formed (e.g., claws) and is grown incrementally (i.e., deposited in layers), changes in an individual's foraging environment would be captured in the chemical signatures in these tissues. To determine whether trace elements can be used as a marker to track movement in terrestrial carnivores, we resolved multi-elemental data at a fine spatial scale in the claw keratin of a model species (Taxidea taxus) using high resolution laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS). The unique chemical signatures we detected in claws suggested that these chemical variations were, in part, a reflection of the chemical environment and were not be attributable to sex or random deposition. Neighbouring claw samples were not more chemically related than distant ones, which suggests that local differences in chemical composition (e.g., habitat type) may have a stronger influence on claw chemistry than large-scale patterns in trace element variation associated with underlying geology. Our findings illustrated that temporallyexplicit chemical profiles in the blade horn keratin of mammalian claws may be used to examine endogenous uptake of trace element signatures from the local environment and serve as tool to assist in reconstructing animal movement pathways.