Scientists have uncovered a case of not so happy feet in penguin populations stressed by human activity.

Researchers tested the stress responses of King penguins in colonies disturbed by humans over 50 years.

They were compared with other King penguins living in areas not visited by humans.

Penguins from the disturbed colonies were better able to cope with the sight of approaching humans, loud noises, and being captured.

Natural selection must have helped them adjust, scientists believe. Over time, stress-sensitive penguins were likely to have walked away and deserted the disturbed colonies, leaving the more resilient individuals behind.

“Our findings report a case of physiological adjustment to human presence in a long-studied King penguin colony, and emphasise the importance of considering potential effects of human presence in ecological studies,” said lead scientist Vincent Viblanc, from the University of Strasburg in France.

Scientists carried out the study on Possession Island in the sub-Antarctic Crozet Archipelago.

They compared 15 breeding penguins from disturbed areas with 18 from undisturbed areas. All penguins selected were brooding a chick aged from two days to one month.

A human approach to 10 metres and loud noises mimicked the effects of tourists, researchers and machinery.

Penguins from disturbed areas were less stressed by noise and approaching humans than those from areas free of human activity. After capture, their maximum heart rate increased by 42 per cent but they recovered more quickly.