CLIMATE MATTERS: COMPARING AVIAN BONE TAPHONOMY IN WARM TEMPERATE VS. SUBTROPICAL ENVIRONMENTS

Investigations of modern avian bone taphonomy are essential for establishing a detailed understanding of the fossil record of birds. Past studies have helped to increase our knowledge of how bird carcasses decay and disarticulate, along with how individual bird bones undergo taphonomic weathering. However, relatively little attention has been given to the role of climate on avian taphonomy. The climate of the environment in which a bone is deposited can play a critical role in its weathering and degradation. In this yearlong study, the rates of taphonomic degradation and degree of physical weathering of age- and sex-grouped chicken carcasses and individual leg bones (femora and tibiotarsi) were compared between two climatically different siliciclastic sites. During the study year, the warm temperate site of Sapelo Island, Georgia, experienced an annual average mean temperature of 66.3⁰F, an annual precipitation of 49 inches, and an average maximum relative humidity of 86%; the subtropical site of Naples, Florida, experienced an annual average mean temperature of 74.5⁰F, an annual precipitation of 53 inches, and an average maximum relative humidity of 89%. Although the decay and loss of soft tissue occurred at the same rate in both localities (15-30 days), the rate of skeletal disarticulation and degree of physical weathering of bones was greater in the subtropical climate than the warm temperate climate. Also, substantially fewer bone elements were preserved after 12 months in the subtropical climate. At both locations, adult male bones (carcass and leg elements) were preserved more frequently and in better taphonomic condition than other age and sex groups, despite the fact that male leg bones lost more mean mass and density than female leg bones. Thus, bird bones deposited in siliciclastic environments in warm temperate climates may have a better chance of becoming preserved in the avian fossil record, which could be biased toward adult male bones. The data from this study indicate that ambient temperature may play the largest climate-related role in the taphonomic weathering of bird bones and this could have important implications for the preservation potential of avian bones during global warming events.