

Camouflage influences life-and-death decisions that animals make




In complex environments it is hard for animals to perfectly match their background. When an animal’s camouflage is poor it has a higher risk of being detected and eaten by a predator, so it should more readily flee from an approaching threat. The researchers therefore set out to test whether the distances at which birds fled from their nests on the exposed ground was related to the camouflage of their plumage and eggs.


The team photographed the adult birds and eggs using specially-calibrated digital cameras. Sophisticated computer models of animal vision were used to map images to each predator’s visual abilities. Birds have high colour sensitivity and can see ultra-violet wavelengths. The banded mongoose has relatively poor colour vision and can only see colours equivalent to blues and yellows.

Study author, Jared Wilson-Aggarwal, a PhD researcher at the University of Exeter’s Environment and Sustainability Institute, said: “Plovers, coursers and nightjars nest on the bare ground during the Zambian dry season. Temperatures can get very high and if approached by a predator the adult bird has to make a hard decision to either, sit tight and continue shading their eggs or to flee the nest and prioritise their own survival.

“Our results suggest that camouflage is able to mitigate not only predation risk but also thermal risks, by permitting adults to shade their eggs for longer when the risk of them overheating is highest.”

Martin Stevens from the University of Exeter who, along with Claire Spottiswoode from the University of Cambridge, co-led the project said: “Our study shows how animals monitor their own camouflage and that of their offspring, and use this to guide how they behave. It complements a small but growing number of studies showing how important behaviour is in facilitating camouflage in nature.”

Claire Spottiswoode from the University of Cambridge added, “Fifty years ago, the pioneering ecologist David Lack predicted that birds with camouflaged plumage should benefit most from sitting tight on their eggs until the very last minute. Nightjars are some of the most beautifully camouflaged animals in the world, and sure enough the African nightjars we studied often only fled their nests when we were at arm’s length!”

Escape Distance in Ground-Nesting Birds Differs with Individual Level of Camouflage is published in the journal The American Naturalist.

Date: 10 June 2016

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