Taphonomic signatures of owls: New insights into micromammal assemblages

Paleoenvironmental reconstructions based on micromammalian assemblages are a commonly used tool in paleoecology and zooarcheology. However, predator prey preferences may bias these assemblages to an unknown degree, thus leading to unreliable paleoenvironmental reconstructions. While attempts at taxonomically identifying micromammal predators through taphonomy has been conducted in the past, none has satisfactorily differentiated between owl taxa. Here we introduce the novel postcranial fracture index and revised versions of digestion indices for obtaining higher taxonomic resolution in taphonomic signatures. We taphonomically analyzed bone assemblages created by owls both in controlled feeding experiments and in the wild. We used blind experiment methodology involving multiple experimenters (each analyzing different bones) to test known and novel indices for reproducible taphonomic signatures within five species of owls (Tyto alba, Asio otus, Athene noctua, Bubo bubo and Strix aluco), Falco tinnunculus and Vulpes vulpes for comparison. We found that experimenter identity has a profound impact on the digestion indices. Nonetheless, the breakage indices and our novel fracture index found significant differences and subjective differences between owl species. Mandible breakage differentiated between Tyto alba and the other, more destructive owls. Postcranial breakage distinguished Strix aluco from the other owls. The postcranial fracture index differentiated between all species except between Athene noctua and Bubo bubo. We recommend a combination of taphonomic indices as a reliable tool for inferring owl species identity of micromammal assemblages.