How do we measure behaviour?
Why do fish behave the way they do, and… how do we measure behaviour?
Studying behaviour in animals is challenging, we can’t simply ask a bird or a fish why they are acting in a certain way, so, we must come up with other methods to interpret behaviour. In SEG we have a wide range of projects focusing on salmonid behaviour and are always working to refine our methods. One aspect of behaviour we are particularly interested in is boldness. Boldness, sometimes referred to as ‘the propensity to engage in risky behaviour’, is a trait that varies widely between individuals and ecological contexts. Measuring boldness boils down to introducing an individual to something new and seeing how they react. In fish we largely see two strategies: freezing or interacting/moving. We can then use these responses to determine how shy or bold an individual is.
In our boldness test we record fish as they encounter a novel environment, initially keeping the fish in total darkness and then exposing them to daylight. Salmonids are sensitive to changes in light and we use this sudden change to elicit a startle response. During a 5-minute period fish that move around the enclosure are categorised as bold and those that freeze are categorised as shy. So far, using this method we have been able to demonstrate differences in boldness across two contexts. 1). Smaller trout are bolder than larger trout and 2). Early migrating trout are bolder than late migrating trout. Determining how, and why, behaviours differ between individuals is key to helping us understand wider concepts such as niche expansion, dispersal and patterns relating to life history traits.
To learn more check out our new paper in Behavioural Processes.
Written by Madeleine Berry, PhD student with the SEG.