Rats ‘talk’ with their mouths full, scientists find
The research gives an insight into the inner emotional life of rats.
Scientists have discovered that rats ‘talk’ when chewing, suggesting that eating may be about more than just filling their stomachs.
Research by Scotland’s Rural College (SRUC) and laboratories from the French National Research Institute for Agriculture, Food and the Environment (INRAE) recorded the sounds as the rats were eating the first meal of their activity phase, the equivalent of our breakfast.
The study follows previous research that discovered that rodents make high pitched chirping sounds known as ultrasonic vocalisations (USVs) during a positive emotional experience or when communicating with other rats.
However, this is the first time that these USVs have been measured during the act of eating.
The sounds were recorded using an ultrasonic microphone, before being transformed into sounds audible to humans. The rats were found to be producing a flat 40kHz, a new type of USV, when chewing their food.
This research gives an insight into the inner emotional life of rats, including how they feel about eating. The scientists will also be able to measure behavioural diversity in the rats to improve their welfare.
SRUC research fellow Vincent Bombail said: “The fact that rats chirp with their mouths full makes us realise feeding is more than about just filling their stomachs - it is also an emotional and social experience, even for laboratory animals.
“Just as we have our dinner table conversations, rats are also communicating something when they eat.”
The research was funded by the Human Nutrition and Food Safety (ALIMH) and Animal Physiology and Livestock Systems (PHASE) departments at INRAE and can be found in the journal Frontiers in Behavioral Neuroscience.
Veterinary practices are being urged to help owners safely dispose of any unused and expired pet medicines - not just antibiotics - during November's Animal Medicines Amnesty. 
