Handling method alters mouse trial results

The way scientists handle mice before an experiment influences their performance, a new study shows.

Two scientists from the University of Liverpool in the UK tested different ways to pick up mice and found that the rodents performed better when they weren’t stressed or anxious.

While this may seem obvious, scientists commonly lift mice by the tail to transfer from cage to testing arena, because it’s the quickest and easiest to catch them.

In a 2010 study, the same researchers, Kelly Gouveia and Jane Hurst, showed this method made the animals stressed. And now, they have followed up by showing how handling mice by their tail before an experiment also jeopardises the reliability of the results.

“A lot of animal researchers do not necessarily always have the background to understand the model they working with, as though it’s just another test tube they can use,” says Western Sydney University behavioural neuroscientist Tim Karl, who was not involved in the study.

“But obviously it is an organism which responds to what you do, what the environment looks like, and it’s important that this message gets out there.”

Gouveia and Hurst handled the mice in three different ways: picking them up by the tail, cupping them unrestrained with an open palm, and guiding them through a clear tube. They also boosted the animals’ comfort by first familiarising them with the handler and the new environment they were going to explore.

To find out which method gave the best results, the pair designed a simple test.

The mice, who were all female, were taken to an area and presented with urine from a male mouse on three separate occasions. They investigated it until the urine became so familiar they lost interest. Then, on the fourth occasion, the scientists presented them with the urine from a different male.

The mice were tested on how well they could distinguish between the two stimuli. And of the three ways the mice were taken to the arena, Gouveia and Hurst found coaxing the mice to crawl through the tube to enter the testing arena gave the best results.

On the other hand, the results from the cupping method were too varied to draw a sound conclusion, and the mice lifted by the tail didn’t show much interest in any of the trials.

“The more anxious they are, the less they’re explorative, and that impacts on the way they learn about their environment,” they report.

Interestingly, the tube worked so well at making the mice comfortable, the scientists suggest it could remove the need for prior familiarisation with the environment and with the handler.

Their findings are published in Scientific Reports.