Dominant carnivore loss benefits native avian and invasive mammalian scavengers

Abstract

Scavenging by large carnivores is integral for ecosystem functioning by limiting the build-up of carrion and facilitating widespread energy flows. However, top carnivores have declined across the world, triggering trophic shifts within ecosystems. Here, we compare findings from previous work on predator decline against areas with recent native mammalian carnivore loss. Specifically, we investigate top-down control on utilization of experimentally placed carcasses by two mesoscavengers—the invasive feral cat and native forest raven. Ravens profited most from carnivore loss, scavenging for five times longer in the absence of native mammalian carnivores. Cats scavenged on half of all carcasses in the region without dominant native carnivores. This was eight times more than in areas where other carnivores were at high densities. All carcasses persisted longer than the three-week monitoring period in the absence of native mammalian carnivores, while in areas with high carnivore abundance, all carcasses were fully consumed. Our results reveal that top-carnivore loss amplifies impacts associated with carnivore decline—increased carcass persistence and carrion access for smaller scavengers. This suggests that even at low densities, native mammalian carnivores can fulfil their ecological functions, demonstrating the significance of global carnivore conservation and supporting management approaches, such as trophic rewilding.

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

“…2021). Further still, recent findings in Australia have demonstrated that ravens, in the absence of top scavengers, scavenged across all four seasons and not only during the cooler months when other resources were low (Fielding et al . 2021).…”

“…For instance, season, along with daily temperatures, humidity, and moisture levels can influence carrion persistence rates via the effects they have on regulating microbial and insect activity (Matuszewski et al 2010;Turner et al 2017;. Moreover, some studies completely ignore seasonal effects by monitoring scavenging dynamics only during one season (Peisley et al 2017;Bingham et al 2018;Cunningham et al 2018;Rees et al 2020;Fielding et al 2022). Therefore, we acknowledge that although the successful design of any robust field study in scavenging ecology is underpinned by temporal aspects (i.e.…”

Scavenging with invasive species

“…Several studies have assessed the scavenging behaviours of larger apex scavengers in Australia, focusing on the Tasmanian devil and dingo. Specifically, studies have noted and/or directly assessed the efficiency of scavenging by Tasmanian devils in terms of their ability to remove carcass biomass (Cunningham et al ., 2018; Fielding et al ., 2021, 2022). The presence of Tasmanian devils at carcass sites can influence the use of carcasses by smaller vertebrate scavengers (Cunningham et al ., 2018; Fielding et al ., 2022).…”

“…Specifically, studies have noted and/or directly assessed the efficiency of scavenging by Tasmanian devils in terms of their ability to remove carcass biomass (Cunningham et al ., 2018; Fielding et al ., 2021, 2022). The presence of Tasmanian devils at carcass sites can influence the use of carcasses by smaller vertebrate scavengers (Cunningham et al ., 2018; Fielding et al ., 2022). Dingoes have similarly been shown to accelerate carcass biomass removal but only in winter when insects were not common (Spencer & Newsome, 2021).…”

Genomic insights into a critically endangered island endemic songbird provide a roadmap for preventing extinction

“…There is a risk that genomic impacts associated with small effective population size and limited dispersal capacity may be contributing to the decline of the King Island scrubtit population . Other threats facing King Island scrubtits include acid sulphate soils associated with drainage for agriculture, wildfires, predation by feral cats, and habitat deterioration through windthrow and sea-level rise (Fielding et al, 2022;Webb et al, 2016). The King Island scrubtit is therefore a priority species for conservation actions under the Australian Government's Threatened Species Action Plan 2022-32 (Commonwealth of Australia 2022).…”