How long a Southern Giant Petrel is likely to live comes down to the length of a particular sequence of DNA in their blood cells, researchers have found.

If these sequences of DNA are long, a giant petrel probably still has a while left before it has to leave this mortal coil. But if they're short, the birds might not have long to go.

In this latest study, published in Behavioral Ecology, scientists found that these sequences of DNA are longer in chicks than in adults.

There's an added burden if you're a male giant petrel. The researchers discovered that male giant petrels have shorter sequences of DNA — called telomeres — than females. This could mean that males may be more prone to die sooner than females. But the team behind the study cannot yet confirm this.

'Here we have a marker which shows where these birds are on their journey through life,' says Professor Pat Monaghan from the University of Glasgow, co-author of the paper.

Telomeres are protective caps at the ends of chromosomes, found in all sorts of creatures like rats, elephants and people. Each time a cell divides, its telomeres get shorter, so that eventually the telomere doesn't work anymore, and the cell either dies or loses the ability to divide.