Camouflage predicts survival in ground-nesting birds.

Claire N Spottiswoode,Jared Wilson-Aggarwal,Martin Stevens,Jolyon Troscianko

doi:10.1038/srep19966

Claire N Spottiswoode, Jared Wilson-Aggarwal + Show 2 more

Open Access

https://doi.org/10.1038/srep19966

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Abstract

Evading detection by predators is crucial for survival. Camouflage is therefore a widespread adaptation, but despite substantial research effort our understanding of different camouflage strategies has relied predominantly on artificial systems and on experiments disregarding how camouflage is perceived by predators. Here we show for the first time in a natural system, that survival probability of wild animals is directly related to their level of camouflage as perceived by the visual systems of their main predators. Ground-nesting plovers and coursers flee as threats approach, and their clutches were more likely to survive when their egg contrast matched their surrounds. In nightjars – which remain motionless as threats approach – clutch survival depended on plumage pattern matching between the incubating bird and its surrounds. Our findings highlight the importance of pattern and luminance based camouflage properties, and the effectiveness of modern techniques in capturing the adaptive properties of visual phenotypes.

Highlights

Evading detection by predators is crucial for survival
We show for the first time in a natural system, that survival probability of wild animals is directly related to their level of camouflage as perceived by the visual systems of their main predators
Clutch survival was unrelated to any aspect of egg appearance, supporting our hypothesis that adult plumage provides nightjars with their primary defence against detection. To our knowledge these are the first data to demonstrate a clear link between the survival of individual wild animals in a natural system and their level of camouflage to predator vision

Summary

Introduction

Evading detection by predators is crucial for survival. Camouflage is a widespread adaptation, but despite substantial research effort our understanding of different camouflage strategies has relied predominantly on artificial systems and on experiments disregarding how camouflage is perceived by predators. Kettlewell’s classic experiments during the 1950s demonstrated that dark, melanic morphs of the peppered moth Biston betularia were more likely to be recaptured when released in areas with trees blackened by industrial pollution, and further experiments implicated birds as the selective agent underlying the spread of melanic forms[6] While this revealed a correlation between coloration and survival, neither Kettlewell’s experiments nor numerous subsequent studies[7,8] have either quantified peppered moth camouflage to predator vision, or shown how each individual’s level of background matching directly predicted its survival. We demonstrate that the survival of ground-nesting birds’ clutches in Zambia is directly linked to their degree of background matching camouflage, as modelled through multiple predator visual systems. Camouflage was quantified in terms of luminance, pattern and colour metrics based on their main predator’s visual systems using calibrated digital image analysis[9]

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