“We know that animals, like people, have different personalities, meaning that they vary consistently in their behaviour, but we don’t yet understand how animals with different personalities respond to change,” said Dr Fürtbauer, who is based in the College of Science.

“With increasing human activity all over the world, animals have to deal with many more and many different changes happening very quickly. Understanding how animals adapt to such changes is therefore a major and outstanding question for biologists.”

Generally, individuals respond to a potential threat with an increase in stress hormone levels – known as a ‘physiological stress response’ and this increase in stress hormones can affect the way that individuals behave under threat – known as the ‘behavioural response’.

Over five weeks, Dr Fürtbauer’s team experimentally manipulated the fish’s perceived predation risk by repeatedly showing them a robot that resembled a heron, a natural predator of the sticklebacks.

They wanted to see if the fish’s behaviour, and the fish’s stress hormone levels changed in response to the predator, and if so, if their personality had anything to do with the way they responded.

“We collected data on behaviour by tracking the fish movements from video, and measured the physiological stress response by measuring the amount of stress hormones the fish released into the surrounding water via their gills.”

The team found consistent individual behavioural and hormonal responses – in other words, the fish showed behavioural and physiological personalities. But they also found that the behaviour and hormone levels were linked – fish were shyer on days they had higher stress hormone levels.

The most important finding, however, was that fish with different personalities were equally capable of responding to a potentially harmful threat.

The researchers think that this approach – combining clever tracking technology for investigating fish behaviour, and non-invasively measuring their hormone levels from water – will transform the way we study individual differences in physiology and behaviour in small fish as well as how they respond to environmental change.

“Personality, plasticity, and predation: linking endocrine and behavioural reaction norms in stickleback fish” Fürtbauer et al (in press) Functional Ecology.

Pictures © Dr Ines Fürtbauer