Teenage Asian Elephant Mothers Have Larger Families But Shorter Lifespans
Studies conducted on semi-captive Asian elephants show that females that start reproducing in their teenage years die younger but give birth to more calves in their lifetimes than older mothers, according to a press release Friday.
Researchers from the University of Sheffield's Department of Animal and Plant Sciences, conducted these studies on 416 Asian elephant cows in Myanmar (Burma). The research showed that cows that gave birth before the age of 19 were almost two times more likely to die before the age of 50 than those that had their first calf later.
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But these teenage mothers also had more offspring during their reproductive cycle than the older cows.
The average lifespan of an Asian elephant is around 70 years. Females attain sexual maturity early on and can start giving birth as early as 5 years of age. But their fertility peaks when they are 19 years old and then gradually declines. Another interesting find of the research was that if elephant cows gave birth twice during their teenage years, the calves were three times more likely to survive, till they left their mothers, than the calves born to mothers older than 19 years.
So, this suggests that nature intended them to be early mothers who can give birth to more number of calves in their lifetime, the flipside being a shortened lifespan.
These findings can be used to improve fertility among captive and semicaptive Asian elephants, whose numbers are greatly declining, making them an endangered population.
"Understanding how maternal performance changes with age and impacts on later-life survival and fertility is important. Asian elephants are endangered in the wild and low fertility in captivity necessitates acquisition of elephants from the wild every year to maintain captive populations," said Dr. Adam Hayward, of the University of Sheffield's Department of Animal and Plant Sciences. "Our research was carried out on semicaptive Asian elephants working in timber camps in Myanmar. As religious icons in South-east Asia and a key species of the forest ecosystem, their decline is of serious cultural and ecological concern."
Adding to this, Virpi Lummaa, Reader of Evolutionary Biology at the University of Sheffield,said "We rarely get the opportunity to study how other species with a lifespan similar to humans grow old. This study represents a unique analysis of the ageing process in a similarly long-lived mammal. It also supports the evolutionary theory that selection for high fertility in early life is energetically demanding, which accelerates declines in survival rates with age which are typical of most animals."
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