Vertebrate scavenging in Australia is shaped by a complex interplay of bioregional, seasonal and habitat factors

Carcass scavenging by vertebrates is a critical ecosystem service that is influenced by environmental factors such as season and habitat. However, there is limited understanding of the role that these factors play in shaping scavenging patterns across different bioregions. We used camera traps to monitor vertebrate scavengers at 120 kangaroo (Family: Macropodidae) carcasses that were positioned across different seasons (warm/cool) and habitats (open/closed canopy) in three disparate desert, subalpine and temperate bioregions in Australia. Our survey identified 27 species that scavenged carcasses and revealed clear differences in scavenging patterns across the three bioregions. Carcass use was highest for feral cats, birds of prey, corvids and red foxes in the desert bioregion; for reptiles and dingoes in the temperate bioregion and for feral pigs, possums and dingoes in the subalpine bioregion. Bioregional differences in scavenger guild composition explained >4.6 times more variation in scavenger guild dissimilarity than season and >9.8 times more variation than habitat. Further, habitat had few effects on scavenger communities or carcass detection and use, whereas season was a strong predictor of these responses. Across bioregions, there were some general seasonal and habitat scavenging trends, with mammals and birds often using carcasses more frequently in cooler seasons and birds detecting carcasses faster in open habitat. However, there was also extensive within-bioregion seasonal variation. For example, depending on bioregion, some animals scavenged more frequently or detected carcasses faster in warmer seasons (i.e. birds and reptiles). Our results show that vertebrate scavenging is mediated by a complex interplay of environmental variables, especially seasonality, which may operate differently across bioregions. These findings have implications for understanding variability in vertebrate scavenging patterns and, in turn, functionally redundant or complementary scavenging processes.