Random feeding times result in bolder fish

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An unpredictable food supply in early life affects boldness in guppies, according to Leeds researchers.

When faced with an unfamiliar tank, fish previously fed at irregular intervals were more likely to explore their surroundings and less likely to spend time shoaling than those that had received a predictable food supply.

Ben Chapman and colleagues fed fish according to different time schedules so that feeding time was

  • always predictable
  • always unpredictable
  • unpredictable early in life but predictable later on
  • predictable early in life but unpredictable later on

They then tested the fishes' responses to both a new tank and shoal mates: "Spending a greater amount of time away from the safety of the group in order to explore the novel setting ...is a potentially risky business and implies individual boldness", explains Chapman.

The feeding regimes had a marked effect on how adventurous the fish were in a  novel tank and their likelihood of shoaling.

While fish that had a unpredictable food supply spent around 20% of their time hiding when put into a new tank, this almost doubled in fish that had had a predictable food supply.

Differences in shoaling behaviour were also seen, with fish from an unpredictable environment spending much less time shoaling than those with a predictable food supply. The effect of recent experience did not seem to affect the animals though – it was only their early experience that affected behaviour.

Chapman and colleagues conclude that "In predictable environments...it may not pay individuals to take further risks such as exploring novel environments or leaving the shoal. Conversely, individuals raised in unpredictable environments cannot rely on regular food supplies and ...may benefit from taking more risks and actively seeking out foraging opportunities".

The group's results show some similarities to experiments carried out on cichlids, where a diet that fluctuates in quality produces smarter fish, with both sets of researchers commenting that further work is needed to  understand the underlying reasons for how early life experience influences behavioural traits later in life.