Study finds rats ‘suffer from too much daylight’

Just like humans laid low by the winter blues, the rodents are susceptible to a form of seasonal affective disorder, or SAD.

But, proving that the rat really is a creature of the night, it is excess light rather than darkness that disturbs the animals.

US scientists found that rats experience more anxiety and stress as spring approaches and the days grow longer.

Conversely, rats exposed to just a few hours of light a day experience a change in brain chemistry that lifts their spirits.

“We’re diurnal and rats are nocturnal,” explained study leader Professor Nicholas Spitzer, from the University of California at San Diego. “So for the rat, it’s the longer days that produce stress, while for us it’s the longer nights that create stress.”

Rats explore and search for food at night, while humans evolved to hunt and forage in the daytime, said the researchers, whose findings are reported in the journal Science.