Catching rats is about to get easier! Scientists discover a chemical that makes rodents less wary

They are notoriously wily and good at evading capture, but catching a rat in a trap may just have got easier.

Scientists have now discovered a pheromone which calms rats down and makes them less wary.

The researchers wanted to harness the natural pheromones of rats – biological compounds released into the air which the rodents use to exchange information.

The scientists knew at least one of these compounds, when released from the bodies of calm rats, make other rats around them less fearful and more relaxed.

So, to find the individual pheromone which produces this effect, the scientists anaesthetised a calm rat to stop it being alarmed by human contact, and used water to absorb dozens of compounds released from its body.

The pheromone found to be released by a relaxed rat which has an effect on other rats is 2-methylbutyric acid (2-MB), which strangely enough can be found in the aromas of cheese and wine.

When tested on laboratory rats, the pheromone made them more relaxed.

Where they would normally freeze in fear upon hearing a beeping noise which had previously been accompanied by a mild electric shock, rats smelling the pheromone did not behave as fearfully.

They were also more likely to enter a chamber where they knew they could sniff the pheromone than they were to enter a chamber where it was absent.

The pheromone worked on the wild rats which can cause issues in towns and cities too.

A typical wild rat will want to avoid an unknown new object, even when it contains food.

But when researchers laid out trays of food at locations including an urban park and poultry farm, one of which was scented with 2-MB, rats were brave enough to eat a significantly higher proportion of food from that tray.

Based on their results, the study authors say 2-MB, which works on rats in tiny amounts, could be used for humane pest control.

The pheromone could be used to lure urban rats into non-lethal traps, and keep them calm inside while they are moved out of the area where they are causing a nuisance.

Microscopic images from the amygdala, the brain site for regulating fear responses

Dr Yasushi Kiyokawa, co-author of the research, from the University of Tokyo, said: ‘We tested at two different locations to see if wild rats would respond to 2-MB.

‘They responded similarly to our lab rats.

‘Synthetic 2-MB reduced their fear of novel things, or neophobia.

‘This is important because it’s neophobia in urban rats that makes producing effective traps so difficult.’

He added: ‘I believe that by studying the social lives of rats, we might actually uncover something about human social interactions as well.

‘That is one of the motivations behind our latest research topic, which explores in more detail than ever before, an observed phenomenon where rats can affect the emotional state of others around them.’