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Good moods found to be infectious among rodents

Rats can anticipate a positive experience and their excitement is shared by others around them.

Rats engaging in social play

A happy mood experienced by rats when they are tickled can be contagious for the other rats in the group, scientists have found.

Rodents show excitement prior to being tickled by leaping like lambs, animal behaviour researchers have found.

This excitement is passed on to other rats in the same cage, who have not yet been tickled; these rats show more interest when introduced to a tickling hand.

Animal behaviour

Scientists reached their findings in a study investigating the relationship between tickling and play in rats, which has been used for decades to mimic social behaviour and gauge happiness in animals.

The research was led by Scotland’s Rural College in collaboration with the Roslin Institute and the Institut National de la Recherche Agronomique (INRA).

Pairs of cages, each containing two young male rats, were placed together, with one animal in each cage being either tickled or handled without tickling each day. The other rats in each cage were not touched during the experiment.

The scientists studied the behaviour of all the rats five minutes before they were either tickled or not, for a total of 10 days.

They also recorded the sounds – ultrasonic vocalisations (USVs) – that rats express during handling, and whether these USVs were positive or negative.

Rats showed excited before being tickled, researchers found, and the positive mood induced by tickling was contagious – rats that were not tickled at first went on to show interest in being tickled.

Shared experience

Previous studies by the same group have shown that rats enjoy tickling and produce sounds associated with pleasure.

The research, published in the journal Applied Animal Behaviour Science, aids understanding of animal welfare will contribute towards good welfare practices.

It was funded by the Biotechnology and Biological Sciences Research Council and the Scottish Government’s Rural Affairs, Food and Environment Research Strategy.

Tickling mimics social play in rats, which they enjoy. These results show a contagious effect for tickling, giving us valuable insight into how rodents respond to positive experiences for themselves and others.

Professor Simone Meddlethe Roslin Institute

** The Roslin Institute receives strategic investment funding from the Biotechnology and Biological Sciences Research Council and it is part of the University of Edinburgh’s Royal (Dick) School of Veterinary Studies. **

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Link to the scientific paper