Taphonomy of mammals remains accumulated by New World vultures in Northwestern Patagonia: implications in archaeological sites formation

BALLEJO, FERNANDO; FERNANDEZ, FERNANDO JULIAN; MONTALVO, CLAUDIA INES; DE SANTIS, LUCIANO JOSÉ MARÍA

San Rafael

Conferencia; 12da conferencia internacional icaz; 2014

The scavenger birds can feed on large to small-size vertebrates and they may contribute in the archaeological site formation. They could introduce an equifinality problem, because their bone accumulations may be confused with concentrations achieved by human activity. In order to evaluate the modifications in bones produced by New World vultures, we analyzed the taxonomic composition and taphonomic aspects of pellet samples (531) of three species from Northwestern Patagonia (Cathartidae: Vultur gryphus, Coragyps atratus and Cathartes aura). Also, nine sheep (Ovis aries) which died naturally in the field, and one sheep that was placed intentionally by us, were analyzed immediately after their death. All of them were quickly eaten by C. atratus, V. gryphus and some raptor birds (Caracara plancus and Milvago chimango). In the New World vultures pellet samples, O. aries and Lepus europaeus were the most common prey. Bones recovered includes mostly skeletal elements from autopodia and teeth with high levels of breakage and heavy evidence of digestive corrosion. On the other hand, sheep carcasses were scavenger by vultures in the first six hours after death. Mandibles were separated from the skull and proximal hindlimbs and forelimbs bones were connected by ligaments, but separated from the axial skeleton or joined by leather. Vertebrae and ribs show signs of breakage. Marks and notches were found mainly in pelvises and scapulae. The New World vultures produce assemblages with bias on anatomical representation of ingested skeletal elements and bones recovered have strong levels of modification. Undigested bones of sheep scavenger by New World vultures were quickly exposed to the weathering agents and found with a particular degree of dispersion. Pectoral and pelvic girdles were the skeletal elements that show marks and other bones were mainly broken.