Carcass use by mesoscavengers drives seasonal shifts in Australian alpine scavenging dynamics

Abstract

Context. Carrion is a high-energy and nutrient-rich resource that attracts a diverse group of vertebrate scavengers. However, despite the carrion pool being highly seasonal in its availability, there is little understanding of how scavengers utilise carcasses across all four seasons. Aim. To assess how season influences carcass-detection times by vertebrate scavengers and their rates of scavenging. Methods. We used remote cameras to monitor vertebrate scavenging at 15 eastern grey kangaroo (Macropus giganteus) carcasses in four consecutive seasons (summer, autumn, winter, and spring; total 58 carcasses) in the Australian Alps. Key results. In total, 745 599 remote-camera images were captured, within which 34 vertebrate species were identified, nine of which were recorded to actively scavenge. Time to first detection of carcasses by vertebrate scavengers was 5.3 and 9.6 times longer during summer (average 144 h) than during spring (average 34 h) and winter (average 24 h) respectively. Rates of vertebrate scavenging were highest in winter and spring, with brushtail possums (Trichosurus vulpecula) accounting for 78% of all scavenging events during winter, and ravens (Corvus spp.) accounting for 73% during spring. High rates of carcass use by these mesoscavengers may reflect a scarcity of other food sources, the demands of their breeding season, or a relative absence of scavenging by larger dominant species such as dingoes (Canis dingo) and wedge-tailed eagles (Aquila audax). Conclusions. These findings demonstrate the highly seasonal nature of vertebrate scavenging dynamics in an alpine ecosystem, and that mesoscavengers, not apex scavengers, can dominate the use of carcasses. Implications. Accounting for the effects of season is integral to understanding the way animals utilise carcasses in alpine and other strongly seasonal environments; and for developing further our knowledge of ecosystem processes linked to decomposition.