For many people, a hot bath is the perfect way to end a stressful day – and according to a new study, the same is true for monkeys.

Scientists observing a group of monkeys famous for bathing in hot springs have found their unusual behavior decreases stress, as well as helping them stay warm.

Japanese macaques – also known as snow monkeys – are the world’s most northerly species of primates, apart from humans.

They are adapted to living in extremely cold climates, with thick layers of fur that keep them warm through the winter months.

Though observers have long assumed the monkeys were using these spas to warm up, no researchers had ever tested this assumption.

To investigate the monkey spas in greater depth, a team of researchers led by Dr Rafaela Takeshita of Kyoto University took fecal samples from bathing macaques to analyze levels of glucocorticoids – hormones associated with stress and body temperature management.

In total, the scientists studied 12 adult macaques and followed them during the spring birth season and winter mating season.

They found that taking a bath did indeed reduce levels of these hormones, and suggested that monkeys who regularly bathed not only lowered their stress levels, but also improved their reproductive capacities and extended their survival rates.

"This indicates that, as in humans, hot spring bathing has a stress-reducing effect in snow monkeys, which also increases their longevity," said Dr Takeshita.