Long-term UVB exposure promotes predator-inspection behaviour in a fish.

Ultraviolet-B radiation (UVB) reaching the earth's surface has increased due to human-caused stratospheric ozone depletion. Whereas the harmful effects of UVB on aquatic organisms are well studied at the molecular and cellular level, recent studies have also begun to address behavioural changes caused by sublethal amounts of UVB. However, the behavioural consequences of long-term exposure to ecologically relevant UVB levels over several life stages are virtually unknown, particularly with regard to predator-prey behaviour. We found increased predator-inspection behaviour together with a smaller body length in three-spined sticklebacks (Gasterosteus aculeatus) after fish were exposed for about seven months to natural sunlight conditions with enhanced UVB, compared with full siblings exposed to natural sunlight only. The observed change in antipredator behaviour may reflect a direct behavioural response mediated through UVB-induced oxidative stress during development. Alternatively, the smaller body size in UVB-exposed fish may result in an increased inspection effort allowing them to spend more time foraging. Our findings suggest that, within the scope of environmental change, UVB radiation constitutes an important stress factor by eliciting behavioural responses that influence crucial ecological processes, such as predator-prey interactions.