TEMPORAL MEGABIAS: LATITUDINAL CONTROLS ON TIME-AVERAGING OF TERRESTRIAL LARGE-MAMMAL DEATH ASSEMBLAGES

Maximum survival durations of bones on landscape surfaces are primary controls on the ecological data captured by terrestrial vertebrate death assemblages. Here, I test for differences in time-averaging of modern large-mammal death assemblages in tropical, temperate and arctic settings. I also test for climatic and ecological controls on the weathering stage frequency distribution of landscape bone accumulations across this latitudinal gradient. To test the survival durations of bones on arctic landscapes, I radiocarbon-dated 50 antlers, bones, and teeth of adult and neonatal caribou (Rangifer tarandus) recovered from bone surveys of arctic tundra (Arctic National Wildlife Refuge, AK). To test for differences in time-averaging durations across latitude, these new data are paired with existing data on survival durations of ungulate bones from high arctic, temperate, and tropical landscapes. Time-averaging potential increases by orders of magnitude between latitudinal bins: maximum bone survival reaches decadal time-scales in the tropics, centennial time-scales in temperate regions, and up to millennial time-scales in arctic settings. While over-all time-averaging duration has strong climatic drivers, the frequency distribution of bone Weathering Stages is strongly influenced by ecological history, particularly species’ population stability (or lack thereof). Ecosystems with different time-averaging durations can produce highly-similar Weathering Stage frequency distributions, illustrating that such comparisons are not necessarily simple. Environmental and ecological settings with faster bone recycling rates (the tropics) may be particularly adept at capturing ecological changes across decadal timescales, without significant blurring by generations from prior centuries or beyond. Colder ecosystems from higher latitudinal settings (temperate and arctic settings), offer extended observational windows, which are particularly insensitive to high-frequency ecological variability. Acknowledging differences in temporal resolution among death assemblages is an important component of any taphonomic and/or ecological comparison.