Current global warming affects the composition and dynamics of mammalian communities and can increase extinction risk.  Paleoecological research can clarify how past climates and environments have changed over time and test ecological hypotheses of relevance to neontologists.  Specifically, the fossil record provides a record from which long-term responses of climate change can be determined.  Stable isotopes preserved in fossil mammal teeth are used to assess dietary niche partitioning, the magnitude of ancient floral change, relative aridity, relative seasonality, and relationships between these factors during the late Cenozoic.  Previous work has focused on clarifying community level responses to interglacial warming during the Pleistocene.  This work builds on that body of work by specifically examining how individuals and closely related taxa partition their niches seasonally over time, with an emphasis on mixed feeders.  Specifically, carbon isotopes from serial samples of mixed feeders within the same species are compared to assess if individuals have disparate dietary strategies.  Additionally, serial samples from mixed feeding taxa within the same family are examined to assess if closely related taxa partition their niches differently from one another.

Results/Conclusions

Stable carbon isotope data demonstrate that changes in floral composition associated with climate change can result in dietary niche shifts, including the partitioning of diets seasonally at the species level.  Specifically, some individuals consume primarily C₃ resources while others consume mixed C₃/C₄ resources and/or C₄ resources, throughout the entirety of approximately one year.  These results demonstrate that individuals of the same species can have a diversity of dietary strategies.  Additionally, mixed feeders within the same family potentially partition their dietary resource seasonally.  Furthermore, these results underscore the importance of examining the effects of climate change on seasonal dietary resource partitioning, as changes in dietary niches may occur at different temporal scales.  Understanding how mammalian herbivores responded to climate change over the long term is critical to assessing possible biotic responses to current global warming.