Scientists learned guppies have distinct personalities — by scaring the heck out of them

A group of researchers have learned that Trinidadian guppies have distinct personality differences between individuals — and they did it by measuring their reactions to being terrified by a facsimile of their most common natural predators.
Researchers observed distinct and consistent differences in the personalities between individual Trinidadian guppies. (Photo courtesy Tom Houslay)
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A group of researchers have learned that Trinidadian guppies have distinct personality differences between individuals — and they did it by measuring their reactions to being terrified by a facsimile of their most common natural predators.

The findings came from a study out of the University of Exeter in England, and were published in this week's issue of the journal Functional Ecology.

The researchers wanted to learn more about the nature behind guppies' "animal personalities" and possible variances between individual fish.

"The term 'animal personality' means individuals from the same species, from the same populations, behave differently, and these differences are consistent over time. So what we do is we put them into new and unfamiliar situations and see how their behaviour changes," lead researcher Tom Houslay told As It Happens host Carol Off.

This composite image shows the comparative size between a Trinidadian guppy, bottom left, and two of its natural predators - a cichlid fish, bottom right, and a heron. (Photo courtesy Tom Houslay)

The researchers took about 100 Trinidadian guppies and periodically placed their fish into a separate tank holding a live cichlid — a much larger fish and natural predator of the guppy.

The team also took a lawn ornament model of a heron and dipped it into the tank, causing the guppies to scatter.

Houslay described how he took a garden ornament of a heron, "chopped the head off of it" and strapped it to a pulley system, effectively turning it into a variation of the famous drinking bird ornament.

They named the cichlid Big Al — after research team leader Alastair J. Wilson — and the heron model Grim.

They also periodically deposited guppies from one fish tank to another one with slightly different aquarium ornaments and shelters to observe how they adapted to being placed in a new and unfamiliar setting.

The researchers found that every fish inevitably became "more cautious" shortly after an encounter with Big Al or Grim, but certain, braver fishes would venture out from under shelter sooner than others. What's more, the brave guppies would consistently overcome their fears before other, more timid members of the test group.

"These personality differences mean there are meaningful differences between these individuals and how they behave," said Houslay. He hopes to learn more about what causes these differences, whether they're linked to hormones, physiological differences or other factors.

One might be worried about the mental fortitude of the guppies after being subjected to these sorts of tests, but Houslay assured Off that their lives in the lab were relatively serene.

"Guppies live in really high densities, and they're tiny little fish. So they make a really good snack for a huge variety of predators. We subjected them to a small stress every three days for four weeks. But in the wild their lives would be a constant nightmare of harassment from predators," he said.

With the publication of the study, however, the guppies won't have to worry about any more herons on a feeding frenzy.

"Big Al and Grim have both been retired for now. So the guppies are safe for the time being," said Houslay.