You might be familiar with apex predators, but what about apex scavengers? These large animals play an equally important role in ecosystems as nature’s clean-up crew, feeding on carrion (animal remains) and preventing the spread of disease.
Apex scavengers can contribute to structuring scavenger communities and often dominate trophic levels (the position an organism sits in within a food web). But little is known about their selective feeding behaviours – specifically, which parts of carcasses they target and whether this changes throughout the seasons.
“We knew that recent work had found that wild animals feed quite specifically to meet their nutritional needs and thought this would be a fantastic opportunity to test this in carnivores – which have had little to no research in this space,” explains Niraj Meisuria, a PhD student working in The University of Sydney’s Disease Ecology Lab.
So Meisuria, as well as other researchers from The University of Sydney and the University of Glasgow, deployed 40 eastern grey kangaroo carcasses across the Wolgan Valley, on the edge of the Greater Blue Mountains National Park in New South Wales.
Twenty carcasses were distributed in both the warm and cool seasons so the scientists could study whether temperature influenced feeding behaviours. The kangaroos were sourced from damage mitigation culls in the local area, with the carcasses displaying evidence of heavy parasite loads.
The researchers then set up camera traps near the carcasses and left them for 30 days.
Caught on camera
The cameras picked up the activity of dingos and wedge-tailed eagles (both apex scavengers), as well as red foxes (a smaller, more opportunistic scavenger, referred to as a mesoscavenger).
The findings, published in the Royal Society Open Science journal, showed that although the apex scavengers demonstrated clear feeding preferences, they all targeted non-protein energy sources.
Wedge-tailed eagles frequently prioritised the head and abdomen of carcasses, feeding on the head more often than the other species in the study. Dingoes favoured the tail of the kangaroo.
Both also out-competed red foxes for these body parts, indicating that apex scavengers could impact the survival and fitness of mesoscavengers.
However, the team discovered that the behaviour of the apex scavengers shifted during the seasons, with both the eagles and dingoes feeding more on the abdomen in the cool season.
As decomposition of the carcasses progressed, the eagles' and dingoes' favoured body parts changed – whereas foxes showed little change.
“The most significant finding was to note – for the first time – selective feeding behaviours in scavengers and how this is impacted by season and through time,” says Meisuria.
“This study provides evidence that it’s not just herbivores that feed selectively to meet nutritional targets. It’s always super exciting for your suspicions about a natural phenomenon to be proven right.”
Top image: a red fox caught on one of the camera traps next to a kangaroo carcass. Credit: Meisuria, N. et al.
