This is a multi-individual (n = 11), stable carbon and nitrogen isotope study of bone collagen ( δ 13 C col and δ 15 N col ) from the giant beaver (genus Castoroides ). The now-extinct giant beaver was once one of the most widespread Pleistocene megafauna in North America. We confirm that Castoroides consumed a diet of predominantly submerged aquatic macrophytes. These dietary preferences rendered the giant beaver highly dependent on wetland habitat for survival. Castoroides ’ δ 13 C col and δ 15 N col do not support the hypothesis that the giant beaver consumed trees or woody plants, which suggests that it did not share the same behaviours as Castor ( i . e ., tree-cutting and harvesting). The onset of warmer, more arid conditions likely contributed to the extinction of Castoroides . Six new radiocarbon dates help establish the chronology of the northward dispersal of the giant beaver in Beringia, indicating a correlation with ice sheet retreat.

any adhered oils. Wing δ 15 N was similarly influenced by pigment (range 0.3‰), but this effect was not reduced through washing. We recommend future isotopic studies of monarchs and other butterflies for migration research to use the same region for subsampling consistently and to wash samples with solvent to reduce isotopic variance related to uncontrolled variance in discrimination (δ 2 H, δ 13 C, δ 15 N) and/or adsorbed water vapor (δ 2 H). These data also need to be included in description of methods.

Cervids living in high latitudes have evolved to thrive in ecosystems that experience dramatic seasonal changes. Understanding these seasonal adaptations is important for reconstructing cervid life histories, ecosystem dynamics, and responses in the distant and not-so-distant past to changing seasonality caused by climate change. Cervid antlers provide a rare opportunity for insight into faunal seasonal ecology, as they are grown and shed each year. Stable isotopes of carbon and nitrogen measured directly from antlers have the potential to provide seasonal dietary data for individuals. If the isotopic signals in bone and antler are controlled by the same metabolic processes, then the stable carbon and nitrogen isotope compositions of collagen (δ13CColl and δ15NColl) from incrementally grown antler tissue provide time-constrained dietary signals from the spring and summer growth season. Bone, by comparison, provides an average signal over several years. The amino acid (glutamate and phenylalanine) δ15N in antlers from modern captive caribou showed similar trophic discrimination factors to earlier results for other collagenous tissues (bone, tooth dentin, and cementum). Hence, growth rate was not the primary control on the stable isotope composition of antler collagen. We applied this knowledge to assess seasonal shifts in Quaternary fossils of three Cervidae species: elk (Cervus elaphus), moose (Alces alces), and caribou (Rangifer tarandus). Paired antler–bone δ13CColl and δ15NColl from the same individual were used to identify differences between summer and annual diet and ecology. Intra-antler isotopic variability from serially sampled antlers was used to examine seasonal dietary shifts and specialization.

Here, we present stable carbon and nitrogen isotope data for Pliocene-age (i) plant macrofossils and (ii) bone collagen from High Arctic Dipoides sp. subfossil remains. The specimens originate from a peat deposit at the Beaver Pond fossil site, located on Ellesmere Island (locally known as Umingmak Nuna, meaning "land of muskoxen"), situated within the Canadian Arctic Archipelago (78° 33′ N, 82° 25′ W) (Fig. 1). We reconstruct High Arctic Dipoides sp. palaeodiet within the context of coeval terrestrial and freshwater plant macrofossil remains excavated from the same ~ 4 Ma old peat layer. The Beaver Pond site provides a very rare opportunity for such a palaeodiet reconstruction using coeval herbivore and plant remains.