Quirks and Quarks

Tickling rats to improve animal — and scientists' — welfare

Researchers are listening in on rat giggles, and that’s a good thing for all kinds of science.

Researchers are listening in on rat giggles, and that’s a good thing for all kinds of science.

A rat being tickled in Emma Robinson's lab. Rats emit an ultrasonic "giggling" sound when tickled, and that can give cues to their overall levels of happiness. (University of Bristol)

Originally published on September 26, 2020.

Tickling rats on their tummies might seem more like play time, but in Emma Robinson's lab at the University of Bristol, it's serious science.

When rats are tickled, they let out an ultrasonic giggle, and Robinson wanted to see if that giggle was a genuine sign of happiness, or just an involuntary reaction to being tickled.

"We asked the question, so is it that the vocalizations that the rat emits are a reflection of their individual positive experience, or like humans, do they laugh irrespective of whether they like it?" Robinson told Quirks & Quarks host Bob McDonald.

As rats and mice are widely used in laboratory experiments, it's crucial for researchers to know whether the animals are having a positive or negative experience. And that can often be difficult to determine. "It's actually very hard. How do you ask an animal whether they like something or not?" said Robinson.

By knowing whether or not these giggles are a true signal of happiness, researchers can better assess the animals' needs.

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The research was published this week in the journal Current Biology.

Tickling to simulate rats natural play

Robinson and her team had to tickle several lab rats during a behavioural test, to see whether the rats were truly happy being tickled.

"When we're tickling a rat we are trying to mimic their own natural social interaction. And when young rats play with each other, they do this thing we call rough and tumble play," she said. "And so we use our fingers to simulate that sort of behaviour. So you take your rat and you run your fingers over its back, and you flip it over and tickle its belly."

Tickling the rats simulates their natural rough and tumble play, where rats jump on each others backs and stomachs and use their mouths and paws to "tickle" each other. (University of Bristol)

Then, the team recorded the ultrasonic giggling sound, and compared the amount of giggles to the happiness levels shown in the test. Sure enough, the rats who giggled the most had the most positive experience being tickled.

"We actually had one rat who found the response so positive that it was actually giving out anticipatory laughter. So when it was put in the box where it was going to be tickled, it started to emit these vocalizations before we'd even started tickling it," she said.

Giggles as ways of measuring happiness

Now that the researchers know these giggle sounds are a true sign of happiness, Robinson wants to check for these noises in other situations to determine whether the animals like something or not.

"What we think is that you could actually be recording these ultrasonic vocalizations and the number of vocalizations in this particular range would tell us how positive they find the experience," she said. This is not only important for the animal's overall welfare, but for the quality of the science being produced.

Tickling the rats also helps to make the researchers happy, too.

"It's definitely good for the researchers," said Robinson. "I still find it incredibly rewarding that you can tickle them, and then they come back to you to ask for more tickling, I find that fantastic."

Produced and written by Amanda Buckiewicz.