Among birds, long life is common for parents that get help with childcare. This finding, published this week, was undertaken by researchers from the universities of Lund and Oxford who reviewed data from more than 9000 studies.
Parenthood can be tough. In the animal kingdom, species that care for many offspring die young when compared with species that care for fewer offspring. But having 'helpers' that assist with childcare changes things, as happens in species that raise young in groups. In these group-living species, parents produce lots of offspring and live a long time. New research shows that this happens because helpers take over the bulk of parental care.
Professor Philip Downing of Lund Unviersity said: 'A common pattern in group-living species is that parents do not care very much for their own young. Instead, helpers are responsible for feeding and protecting the young. The fact that parents avoid this work-load means that they can reproduce again and again and still live a long time.'
Some group-living species take this to the extreme, with parents that always rely on helpers for offspring care. For example, ant and termite queens provide no parental care, live for decades, and produce thousands of offspring. While these species are fascinating, it is impossible to tell if helpers are the secret to their longevity. To do this, you have to compare the survival and parental care of breeders with and without helpers.
Downing, his Lund colleague Professor Charlie Cornwallis, and Professor Ashleigh Griffin from Oxford's Department of Zoology focused their review on 23 bird species where some parents get help raising their young, while other parents go it alone. These species occur across the globe and include long-tailed tits in Sweden, sociable weavers in Southern Africa and the Seychelles warbler that occurs on a few islands in the Indian Ocean.
Professor Ashleigh Griffin, said: 'This paper is latest in a series produced by a team that first started working together in the Zoology department 10 years ago. We have been using patterns across species to understand why some species rely on helpers to raise offspring successfully. This strategy is relatively rare - so why does it evolve in some species and not others? This question gets to the heart of how cooperative behaviour evolves in nature more generally - when should organisms give up their own reproductive success to help others?'
'Helpers give up chance to disperse and breed to stay at home and look after their brothers and sister.. but confusingly, they dont seem to have any effect on the numbers of siblings produced from the nest, so why do they do it? The analysis published in this paper shows that helpers have an effect on the lifespan of their mother, which in turn results in more swings being produced over her lifetime.'