What's on the menu? Examining native apex- and invasive meso-predator diets to understand impacts on ecosystems.

Abstract

Understanding how carnivores impact ecological communities is essential for guiding effective management actions and conserving biodiversity. Quantifying predators' diets, including prey selectivity, allows for the assessment of the relative effects native and invasive predators may have on prey populations. In Australia, populations of a native, terrestrial apex predator, the dingo Canis dingo/C. familiaris, and introduced and invasive subordinate mesopredators, the European red fox Vulpes vulpes and feral cat Felis catus, co-occur, but there is limited understanding of their relative impacts on native and invasive prey in different ecosystems. To assess the possible effects of dingoes, foxes and cats on prey, we examined their diet and prey selectivity across a ~10,000 km² semi-arid mallee ecosystem. Using macroscopic scat analysis, we identified strong dietary niche separation. Larger-bodied dingoes primarily consumed large marsupial herbivores, whereas foxes and cats primarily consumed smaller prey, including introduced and native rodents and birds. Foxes had the broadest diet, and the greatest dietary overlap with cats (O_jk = 0.81), compared with dingoes (O_jk = 0.50) or between dingoes and cats (O_jk = 0.36). Livestock were identified in 2% of dingo and 7% of fox scats. Cats and foxes consumed more than 15 times the volume of small native mammals compared with dingoes, including threatened species such as fat-tailed dunnarts Sminthopsis crassicaudata. Cats and foxes also selectively consumed small mammals relative to their estimated availability and consumed fewer large mammals. In contrast, dingoes consumed fewer birds and more echidnas relative to their availability. Our results suggest limited intraguild competition within this semi-arid ecosystem, as dingoes are primarily exerting top-down pressure on large herbivores, whereas invasive mesopredators are disproportionately impacting smaller prey, including threatened native mammals. Practical implication. Our findings suggest that ongoing conservation management of dingoes, red foxes and feral cats must consider the variation in diets, impacts on prey and ecological roles of these different predator species, and avoid indiscriminate lethal control methods. Quantifying actual, rather than assumed, impacts of predators on threatened native species, large herbivores and livestock is essential to achieve effective and integrated ecosystem management.

Key words

• prey
• predators
• feral cats
• native species
• predator prey relationships
• Ecosystems
• ecosystem management
• predation
• diets
• invasive species
• introduced species
• livestock
• feeding habits
• feeding preferences
• Feeding behaviour
• endangered species
• small mammals
• semiarid zones
• animal ecology
• wild animals
• wildlife conservation
• Biodiversity
• wildlife management
• natural enemies
• feral animals
• domestic animals