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Busy as a mesocarnivore: medium-sized predators with high activity levels at risk from environmental

Mesocarnivores - medium-weight mammalian predators such as red foxes (Vulpes vulpes) and bobcats (Lynx rufus) - spend a lot of their time and energy hunting animals much smaller than themselves. And a study recently published in Nature Ecology & Evolution by Canadian and UK scientists has found that this constant need to forage may mean these animals can't adapt quickly to changes in prey abundance or distribution potentially caused by climate change.

The researchers modeled the scaling of animal foraging time to body size by searching scientific literature for information on how much time different mammalian carnivores are known to spend hunting in a day. They found that very small predators (such as bats, weasels, and stoats) and very large predators (bears, big cats, and wolves) spend less time foraging when compared to medium-sized predators weighing between 1 and 10 kilograms. This is likely because carnivores of this size generally hunt prey much smaller than themselves, so each food item is just a fraction of the energy they need to keep going.

We tend to think of animals like foxes and bobcats as generalists - the red fox's range is distributed across the entire Northern hemisphere, and the bobcat is found in almost every habitat in North America south of the boreal forest. However, as environments and species' numbers and distributions become altered as our global climate changes, these busy mesocarnivores may be more susceptible to negative impacts than we think. They simply may not be able to adapt to changes in prey quality or quantity quickly enough and without constant energy inputs, we may begin to see population declines or range loss of these charismatic little carnivores.

For more information:

  • Rizzuto, M., C. Carbone & S. Pawar. 2017. Foraging constraints reverse the scaling of activity time in carnivores. Nature Ecology & Evolution: online. doi:10.1038/s41559-017-0386-1. Link to paper.

  • Here is a good write-up about the publication and its findings by Julia John of The Wildlife Society

And for an interesting examination of the role mesocarnivores play in food webs, check out this publication:

  • Roemer, G.W., M.E. Gompper, & B. Van Valkenburgh. 2009. The ecological role of the mammalian mesocarnivore. BioScience 59: 165-173. Link to paper.

Art by me. Thanks for the inspiration Rizzuto et al!

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