Influences of seasonal prey availability and anthropogenic landscape on small-vertebrate based palaeoecological reconstructions: a case study from the mid-late Holocene transition at El Mirador cave (Sierra de Atapuerca, Spain)

Birds of prey and carnivorous mammals are among the primary accumulating agents of faunal remains, mainly isolated bones and teeth in the karst sediment sites. The microvertebrate remains from their feces and pellets tend to be usually dispersed in the sediment at El Mirador cave (Atapuerca, Spain). Although, twenty small accumulations have been recovered in the Chalcolithic (MIR5) and Bronze Age (MIR4) levels. These accumulations contain an extraordinary number of bone remains of amphibians and reptiles, together with small-mammals and birds. Previous taphonomic study done on the most significant accumulation from MIR4 identified it as a pellet produced by a medium-large owl. Here we describe for the first time the whole sample of pellets recovered from El Mirador cave, describing their faunal content and analysing their similarities by means of statistical analyses. Important variations are evidenced, concerning the taxonomic composition and the number of prey species between different pellets in MIR4, which are put in relation with the owl hunting seasonality and the reproductive cycles of herpetofauna. This study permits to contrast between different hypotheses concerning the seasonality and Holocene anthropization of the landscape, and finally to infer how these possible biases (such as seasonality, predation, ethology, phenology and the annual activity of prey species) can affect palaeoenvironmental and palaeoclimatic reconstructions (Habitat Weighting and Mutual Ecogeographic Range methods). The palaeoenvironmental reconstructions using the different seasonal associations indicates changes in the distribution of primary habitats, with increased wet areas between late winter and mid-spring and increased aridity between mid-spring and summer. Palaeoclimatic reconstructions did not reveal significant differences concerning annual or monthly temperatures. The unique faunistic composition of these accumulations is interpreted as a collateral effect of the human impact during the Chalcolithic-Bronze Age transition in Atapuerca area, which forced owls to hunt on less optimal but more seasonally abundant preys.