The study, published in Proceedings of the National Academy of Sciences (PNAS), shows reproducing early in life carries measurable costs.
However, some individuals appear able to circumvent these effects, living long lives and producing many offspring without suffering any ill effects.
The team assessed the cost of reproduction by measuring telomere length, a biomarker of ageing and stress, in 200 female bats over a 5-year period from a colony at Woodchester Mansion in Gloucestershire, monitored continuously since 1959.
Telomeres are pieces of DNA which act as protective caps at the end of chromosomes. They shorten each time a cell divides and are considered a key marker of cellular health.
By tracking telomeres alongside each individual’s breeding history, the team uncovered the short-term costs of reproduction.
“Females that start breeding younger tend to have shorter telomeres, and those with shorter telomeres are less likely to survive to the next year,” said lead author Dr Megan Power, from the UCD School of Biology and Environmental Science.
“This is a clear sign that reproduction comes with costs, even in a species renowned for its longevity.”
Gareth Jones, Emeritus Professor of Biological Sciences, from the University of Bristol's School of Biological Sciences and senior author, added: “Following the same colony across generations gives a rare window into individual lives, letting us disentangle short-term costs from longer term resilience.”
“There appears to be no lasting penalty, if you survive to the next breeding season,” Dr Power said. “Some bats must buffer or repair the damage, showing how remarkably flexible they are in managing the costs of reproduction.”
Professor Emma Teeling, senior author, who leads UCD’s Laboratory of Molecular Evolution and Mammalian Phylogenetics, explained: “Bats bend the usual rules of ageing.
“By pairing molecular biomarkers with this exceptional long-term field study, we can see how mothers balance investment in offspring with their own survival.”
The study pinpoints lactation as the most demanding period during reproduction.
Moving forward the team plans to understand how some bats sustain extraordinary lifespans while raising multiple offspring without the expected costs of reproduction.
“These ‘super-mothers’ have achieved the evolutionary jack-pot, living long healthy lives with lots of offspring. These are the individuals we need to study to uncover their longevity secrets,” said Professor Teeling.
This study was only possible given the lifetime dedication of co-author Dr Roger Ransome, who established the long-term mark-recapture project in Woodchester Mansion and has monitored the bats there for over 60 years.
Dr Ransome was awarded the British Empire Medal (BEM) in last year’s King’s New Year Honours for services to bat conservation earlier this year.
Paper
‘Short- and long-term costs of reproduction revealed by telomere dynamics in wild greater horseshoe bats’ by Megan L. Power, Emma C. Teeling, Gareth Jones et al. in PNAS