The Effects of Climate-Related Stressors on Social Behaviour in Fish

Studentship strategic priority area: Biodiversity
Keywords: fish, social behaviour, climate change, metabolism, foraging

Abstract:
Various forms of social behaviour exist throughout the animal Kingdom, with benefits for predator avoidance, foraging, and reproduction. To date, however, we know almost nothing about how anthropogenic environmental disturbance affects group living in animals. Among the most critical threats to aquatic ecosystems are changes in temperature and oxygen availability due to climate change. Still, nearly everything we know about how climate-related stressors affect physiology and behaviour comes from observations of single animals in the absence of any social context. Now is the time to address this knowledge gap, given existing knowledge of environmental effects on single animals, the development of technologies for tracking of groups of animals and the urgent need to predict how populations will respond to climate change.

The most immediate effect of climate change is an increase in global surface temperatures of 1.5 to 5.8oC by 2100, with localised consequences being more severe. In ectotherms such as fish, warming increases energy demand by elevating standard metabolic rate. Supervisor Killen's work has shown individuals with an intrinsically high SMR are less social, likely because they prioritise food acquisition and so avoid competition with groupmates. In contrast, individuals with lower energy demand prioritise protection from predators and stay closer to conspecifics. Accordingly, a greater metabolic demand stemming from temperature increase could make individuals less social and reduce cohesion of social groups, possibly affecting group foraging, predator avoidance, social learning, migration and any phenomena dependent on group cohesiveness. The maximum metabolic rate of ectotherms and aerobic scope for oxygen-consuming physiological functions are influenced by temperature, often peaking at a thermal optimum. In general, spontaneous activity in ectotherms increases with temperature but then decreases as they approach their critical thermal maximum, a benchmark for thermal sensitivity at which they experience locomotor impairment. Effects of temperature on these variables could alter which individuals become leaders because individual activity and speed are determinants of leader-follower dynamics. Social niche or placement within hierarchies can also feedback to affect traits such as boldness, which in turn can be linked to metabolism, suggesting social interactions could affect tolerance to thermal stress.

To examine these issues, the proposed project will:
(1) examine how temperature and hypoxia affect interplay between behaviour of individual
animals and their social group
(2) investigate how temperature and hypoxia influence social group functioning during group movements, foraging, and predator avoidance
(3) produce a robust movement model of group behaviour that can be applied to a range of environmental conditions and ecological contexts.

The project will use fish as a model study system. Fishes are frequently used as model taxa to study collective behaviour in animals, and the effects of environmental stressors on ectotherms. They occupy aquatic habitats across the globe, play key roles as both predators and prey, and display a variety of social behaviours. By adopting innovative empirical and theoretical approaches and combining behaviour and physiology, this project will be the first to examine how thermal shifts and hypoxia brought on by climate
change will affect social behaviour.