FLESH OFF THE BONES: LATE QUATERNARY BODY SIZE AND COMMUNITY ECOLOGY OF CANIDS USING FOSSIL FRAGMENTS

In the face of climate change, species have options: they can adapt, adjust their range, persist, or become extirpated/extinct. Changing body size is one way to adapt. Size imposes constraints; from metabolism to energy flow through food webs, many important ecological traits can be inferred from body size. Although easy to measure in living individuals, the prevalence of broken and disarticulated specimens makes body size challenging to measure from fossils. Relationships between skeletal structures and mass have been used to estimate size from fossils, but have been limited to only a few elements.

To increase the utility of partial remains in paleoecological study, we established predictive relationships between mass and 24 skeletal measurements across canids using modern osteological collections. These included dental, cranial, as well as limb bone and partial ephiphyses. Modern specimens ranged in mass over one and a half orders of magnitude. Relationships between mass and skeletal measurements had high r-squared values of the log standardized data (> 0.96), moderately low average percent standard error of the estimate (< 23.6%), and low percent prediction error (< 16.5%).

Using these relationships, we calculated the mass of canids from seven Pleistocene and eleven Holocene faunas on the Edward's Plateau, TX. Estimates of mass for the only extinct canid in this region, the dire wolf, were consistent with prior published estimates. The mass of extant species did not change significantly over time; however, an analysis of the canid community before and after the Pleistocene extinction revealed that the Holocene community exhibited a reduction in the abundance of small canids and an increase in medium size canids. These changes altered the size profile of the canid community, and likely its ecological function.findings differ from responses at other localities. Coyotes from the iconic deposits at Rancho La Brea became smaller after the extinction. Differential responses over broad geographic scales suggests that cosmopolitan organisms, such as coyotes, are flexible in coping with change. It is possible that Edward's Plateau canids underwent behavioral adaptations, such as shifts in diet. Ongoing stable isotope analyses on this community will shed further light on canid ecology throughout the Quaternary.