The effects of light pollution on camouflage and colour change

Supervisors

Main supervisor: Dr Martin Stevens
Co-supervisor(s): Prof Kevin Gaston (University of Exeter),Prof Steve Widdicombe (Plymouth Marine Laboratory), (), (), ()

Project enquiries

Email: martin.stevens@exeter.ac.uk
Contact number: 01326 259358

Host institution: University of Exeter

CASE Partner: Zoological Lighting Institute

Project description

Many biological processes are regulated by patterns and spectra of light over space and time, yet over the last century these have been substantially disrupted by dramatically increased levels of light pollution, both urban and rural. Considerable recent research has investigated how light pollution impacts animal behaviour and species interactions. However, this work has generally focussed on terrestrial systems rather than marine ones, and little work has determined how light pollution affects visual signals and related anti-predator strategies. Many species use information regarding environmental light, including how this affects the perception of their surroundings, to guide colour change. This ability occurs over many timescales, from seconds to hours, days, weeks, and months, and is commonplace in nature, from frogs and fish to crustaceans and caterpillars. One of the key functions of colour change is for camouflage against predators, whereby individuals change to match their visual background. This is extremely common in marine animals, including UK intertidal species – an area of the marine zone that suffers considerable light pollution. Colour change for camouflage should be affected by how animals view their visual backgrounds, as well as through predictable temporal light patterns (e.g. day-night) because many species change colour at night. Therefore, light pollution should have a considerable impact on its effectiveness. In addition, higher light levels at night should make prey animals more vulnerable to detection when they would normally be hidden. However, these predictions are yet to be tested in any system. This project will use common intertidal species to investigate the effects of light pollution on camouflage, colour change, and associated behaviours and interactions. It will focus on two main study groups: crustaceans (e.g. crabs) and fish, both of which have been shown to change colour for camouflage and from day to night. The project will first characterise the type and extent of light pollution around UK intertidal zones. It will then determine how changes in lighting, replicating natural moonlight and a variety of commonly used artificial light types, affect colour change for concealment and 24-hour day-night rhythms. This will be done by keeping individuals against controlled background colours and quantifying how light conditions affect the ability and nature of colour change and resulting camouflage to predator vision. In addition, PML has sophisticated mesocosm facilities whereby experiments will be conducted to determine how behaviour (substrate choice, hiding, activity patterns) of crab and fish individuals is affected by light pollution in simulated natural habitats. Experiments can also investigate interactions between species under different lighting regimes. This project will determine how the camouflage, colour change, interactions, and behaviour of many animals will be affected by light pollution types.

References

T. W. Davies, J. P. Duffy, J. Bennie, K. J. Gaston. The nature, extent, and ecological implications of marine light pollution. Front Ecol Environ 12, 347-355 (2014).

K. J. Gaston, M. E. Visser, F. Hölker. The biological impacts of artificial light at night: the research challenge. Phil Trans R Soc B 370, 20140133 (2015).

M. Stevens. Color change, phenotypic plasticity, and camouflage. Front Ecol Evol 4, 51 (2016).

M. Stevens & S. Merilaita. (Editors). Animal Camouflage: From Mechanisms to Function. (Cambridge University Press, 2011).

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