Lions and tigers and bears! Oh my!
It does seem strange to have a carnivores page on a plant ecology website, but sometimes the same questions can be addressed with very different organisms. In this case, Gabriele Cozzi and Femke Broekhuis were interested in how different species of large carnivores coexist – a project that we were privileged to play a small part in.
Although the questions may be similar, the types of mechanism at work can be quite different for different types of organism. A powerful mechanism of coexistence proposed for carnivores is called temporal partitioning, whereby the weaker, more vulnerable species avoid competition with their dominant competitors by being active at different times of day. In particular, it is proposed that lions and spotted hyenas are mostly night-active, forcing the smaller cheetahs and African wild dogs to hunt only by day. It might seem strange that carnivores need to avoid each other, but lions are well known to steal prey and even kill smaller carnivores.
And dance by the light of the moon…
In a remarkable three-year effort, Gabriele and Femke attached GPS collars to all four carnivore species in an area of the Okavango, Botswana. These collars recorded the activity of the animals, so it was possible to see when and how they moved. Surprisingly, although lions and hyenas were always predominantly night-active, the activities of wild dogs and cheetahs were strongly influenced by the moon. Indeed, both wild dogs and cheetahs could spend long periods being night-active, but only when the moon was full. It therefore seems that they avoid night activity because their visual systems don’t allow them to hunt effectively at low light levels rather than to avoid the dominant carnivores.
It’s truly amazing how a new generation of collars equipped with motion sensors and GPS devices are transforming our view of animal movement and shedding new light on old questions.
Cozzi G, F Broekhuis, JW McNutt, LA Turnbull, DW Macdonald and B Schmid. (2012) Fear of the dark or dinner by moonlight? Reduced temporal partitioning among Africa’s large carnivores. Ecology. 93, 2590-2599
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