According to a new research article, fewer children may be the reason behind a long life.

The study, from the University of Gothenburg, Sweden, shows that there is a co-relation between life span and reproduction. Research has demonstrated that the longer birds wait to produce and the number of offspring they have affects their life span.

Also, telomere length decides how long an individual lives.

Telomeres are the protective caps at the ends of chromosomes that protect genetic information on the chromosomes. Length of telomere can give an idea about cell aging.

"This is important, not least for our own species, as we are all having to deal with increased stress," said Angela Pauliny, researcher from the Department of Biological and Environmental Sciences at the University of Gothenburg.

The length of telomeres differs from person to person and depends on both genetics and environmental stress.

The present study was conducted on barnacle geese which are known to live longer. The oldest bird in the study was about 22 years old. Researchers found that birds that live long have the ability to preserve the telomere than the short-lived birds.

One possible reason for this difference might be that birds that live longer are investing more resources in maintaining a healthy body than in reproduction.

"There is a clear correlation between reproduction and ageing in the animal world. Take elephants, which have a long lifespan but few offspring, while mice, for example, live for a short time but produce a lot of offspring each time they try," said Pauliny in a news release.

Each bird in the study was measured twice after every two years. Researchers found that the telomere length was different in both genders.

"The study revealed that telomeres were best-preserved in males. Among barnacle geese, the telomeres thus shorten more quickly in females, which in birds is the sex with two different gender chromosomes. Interestingly, it is the exactly opposite in humans," said Pauliny.

The research article is published in the journal BMC Evolutionary Biology.