Help at the nest means a longer life for mother Seychelles warblers, research reveals.
Mothers who have help raising the chicks from the rest of the family group age slower and live longer than mothers that raise chicks alone.
Cooperative breeding occurs in a wide range of bird species as well as mammals, including humans. It is defined by helpers, often closely related, who do not breed themselves, but instead assist the dominant male and female.
In the Seychelles warbler (Acrocephalus sechellensis), most helpers are female, and help the parents by incubating the eggs and providing food for the chicks.
In a closely studied population of the warbler, researchers have been able to track the survival rate of the birds over time and compare the longevity of the mothers who raise chicks with helpers with those who go it alone, with just the male’s help.
The team, including biologists from the universities of Groningen and Wageningen in the Netherlands, plus colleagues from the UK universities of East Anglia, Leeds, and Sheffield, identified individual warblers by their coloured leg bands, and closely studied their breeding behaviour. The researchers also used telomere length as a measure of the birds’ condition.
Telomeres are areas of repeated nucleotide sequences at each end of a chromosome, which protect it from deterioration.
“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,” explains David Richardson, from University of East Anglia.
“So, we can use it to measure how quickly different birds are ageing.”
The team predicted that the female warblers with helpers at the nest would fare better, because the assistance of helpers reduces the mother’s workload, and presumably her stress levels.
The study examined the association between cooperative breeding and ageing using 15 years of data on the breeding behaviour, longevity and telomere attrition rate of the warbler population.
Male warblers did not seem to benefit as much as females from assistance at the nest, probably because they invest less time and energy in rearing duties. However, for females, especially older mothers, the positive effect was clear.
“We found that older dominant females really benefit from having female helpers,” Richardson says.
“They lose less of their telomeres and are less likely to die in the near future. This shows they are ageing slower than females without helpers.”
The findings, published in the journal Nature Communications, suggest that delayed senescence is a key benefit of cooperative breeding and may help explain why social species such as humans have longer life spans than non-social species.
Tanya Loos is an ecologist and science writer based in regional Victoria, Australia.
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