Birds live longer when they have help raising offspring

Female birds age more slowly and live longer when they have help raising their offspring, according to research.

Studying the relationship between ageing and offspring-rearing patterns in the Seychelles warbler, researchers at UK's University of Sheffield found that females who had assistance from other female helpers benefitted from a longer, healthier lifespan.

The findings help explain why social species, such as humans, which live in groups and cooperate to raise offspring, often have longer lifespans.

"It is well understood that one of the benefits of having relatives' help to raise offspring is that this improves the survival of the young," said Professor Terry Burke, from the University of Sheffield's Department of Animal and Plant Sciences.

"We have now shown that as parents age they decline in their ability to care for their offspring, but having helpers compensates for this effect, allowing the parents to continue to reproduce successfully into old age," Burke said.

The result helps to answer the question of why some animals assist others to reproduce, instead of raising their own offspring, Burke said.

"Finding out more about what causes biological ageing is really important. And, until now, there has been very little known about the relationship between sociality and ageing within species," said professor David S Richardson, from UEA's School of Biological Sciences.

The research team used more than 15 years of data on the breeding patterns of Seychelles warblers living on the small island of Cousin, in Seychelles, to study associations between cooperative caregiving and ageing.

As well as studying how quickly individuals' chances of dying increased as they grow older, the team also used the length of the birds' telomeres as a measure of their condition.

Telomeres are found at the end of chromosomes and act as protective caps to stop genes close to the end of the chromosome being damaged – like the hard plastic ends of a bootlace.

"Our previous work has shown that telomere length can be a good indicator of an individual's biological condition relative to its actual age – a measure of an individual's biological age so to speak. So we can use it to measure how quickly different birds are ageing," Richardson said.

In the Seychelles warbler, the majority of helpers are female - and they assist with incubating the eggs and providing food for the chicks. This means that the parents do not need to do as much work when they have help, Richardson said.

The study was led by researchers at the University of East Anglia (UEA) and the University of Groningen in the Netherlands, in collaboration with the universities of Sheffield, Leeds and Wageningen, and with Nature Seychelles.

"Our results suggest that for the older mothers, there are real benefits to cooperative breeding. Biologically speaking they stay 'younger' for longer, and they are more likely to live longer," said Martijn Hammers from the University of Groningen.

"These findings may help to explain why social species often have longer lifespans," Hammers said.

The study was published in the journal Nature Communications on March 21.