A grey fox in the Calakmul Biosphere Reserve, Mexico - an example of a flexitarian mammal. © Owen Middleton

A black-backed jackal. © Chris Sandom

Research has demonstrated that the ongoing human-driven mass extinction event has particularly affected the world’s most carnivorous mammals, leaving many ecosystems dominated by smaller carnivores with more flexible diets.

Carnivorous mammals play crucial roles in ecosystems across the world but humans compete with them through prey exploitation, habitat modification, and direct persecution which likely began when modern humans expanded out of Africa.

Research by Mr Owen Middleton, Professor Jorn Scharlemann, and Dr Chris Sandom has now demonstrated that the most meat-dependent carnivores, or hypercarnivores (whose diets consist of over 70% meat), have been disproportionately affected by these human impacts.

Over the past 130,000 years hypercarnivores, especially large-bodied hypercarnivores, are more likely to have gone extinct globally or be confined to smaller areas as their ranges decline, whereas smaller carnivores with more flexible diets have mostly persisted.

These selective extinctions and range contractions have resulted in the simplification of native carnivore communities across the world, impacting ecological processes such as nutrient dispersal and vegetation consumption patterns as foraging herbivores would be widely less limited by predation risk.

Mr Middleton said: “We investigated whether the geographical ranges of hypercarnivorous mammals are more restricted than those of less carnivorous mammals, and consequently how the diversity of continent-wide ensembles have been affected.

“We found the global geographic ranges of carnivorous mammals are currently more reduced for species with greater body masses and increased reliance on vertebrate meat, a common occurrence throughout mammalian evolution following disturbances. Basically, if you’re a small, flexitarian carnivore, your chances of persistence in a world dominated by humans have been high. We demonstrated that this occurred consistently across the world, but the magnitude of change varied from continent to continent. Australia suffered the largest relative decline, primarily because of the originally low functional redundancy of the continent’s hypercarnivorous mammals.”

It is believed hypercarnivores have been less able to adapt to the ecological disturbances caused by humans because of their specialised, limited diets and slow life histories. Whereas some smaller mammals with more flexible diets have been able to thrive in unpredictable environments with varied resource availability.

The researchers argue that this knowledge of past changes to carnivorous mammals should inform conservation and there should be an aim to restore functional carnivore communities, where possible across continents.

They recommend enhanced protection of large-bodied hypercarnivorous mammals, as well as identifying regions for reintroductions.

Homogenisation of carnivorous mammal ensembles caused by global range reductions of large-bodied hypercarnivores during the late Quaternary is published in Proceedings of the Royal Society B.