Rodents as Taphonomic Agents: Bone Gnawing by Brown Rats and Gray Squirrels*


  • *

    Portions of this paper were presented as a poster at the 57th Annual Meeting of the American Academy of Forensic Sciences, February 23, 2005 in New Orleans, LA. This research was supported by the National Institute of Justice and the William M. Bass Endowment Fund.

Additional information and reprint requests:
Walter E. Klippel, Ph.D.
Department of Anthropology
250 South Stadium Hall
University of Tennessee
Knoxville, TN 37996


Abstract:  Passive infrared technology was used to film diurnal and nocturnal scavenging behavior of brown rats and gray squirrels at the University of Tennessee’s Anthropological Research Facility. This direct documentation demonstrated that brown rats modified fat-laden cancellous bone while gray squirrels generally gnawed the thicker bone cortices only after fats had leached away. A case study placed in a shaded portion of the Facility indicated the postmortem interval for initial gnawing by gray squirrels was slightly over 30 months. An examination of 53 human skeletons in the William M. Bass Forensic Skeletal Collection revealed that 10 cases had gnaw marks consistent with those made by gray squirrels. One of the 10 cases had been gnawed within 16 months of time-since-death, while the remaining nine had postmortem intervals >30 months. Additional observed modifications made to nonhuman bone by gray squirrels indicate that squirrel gnaw marks on bone can serve as a minimal estimate of time-since-death in a temperate environment similar to that of East Tennessee.