Data from: Changes in the diet and body size of a small herbivorous mammal (Sigmodon hispidus, hispid cotton rat) following the Late Pleistocene megafauna extinction

The catastrophic loss of large-bodied mammals during the terminal
Pleistocene likely led to cascading effects within communities. While the
extinction of the top consumers probably expanded the resources available
to survivors of all body sizes, little work has focused on the responses
of the smallest mammals. Here, we use a detailed fossil record from the
southwestern United States to examine the response of the hispid cotton
rat (Sigmodon hispidus) to biodiversity loss and climatic change over the
late Quaternary. In particular, we focus on changes in diet and body size.
We characterize diet through carbon (d13C) and nitrogen (d15N) isotope
analysis of bone collagen in fossil jaws and body size through measurement
of fossil teeth; the abundance of material allows us to examine population
level responses at millennial scale for the past 16ka. Sigmodon was not
present at the cave during the full glacial, first appearing at ~16ka
after ice sheets were in retreat. It remained relatively rare until ~12ka
when warming temperatures allowed it to expand its species range
northward. We find variation in both diet and body size of Sigmodon
hispidus over time: the average body size of the population varied by ~20%
(90-110g) and mean d13C and d15N values ranged between -13.5 to -16.5‰ and
5.5 to 7.4‰ respectively. A state-space model suggested changes in mass
were influenced by diet, maximum temperature and community structure,
while the modest changes in diet were most influenced by community
structure. Sigmodon maintained a fairly similar dietary niche
over time despite contemporaneous changes in climate and herbivore
community composition that followed the megafauna extinction. Broadly, our
results suggest that small mammals may be as sensitive to shifts in local
biotic interactions within their ecosystem as they are to changes in
climate and large-scale biodiversity loss.