March 7, 2014
In The Elephant World Teen Mothers Die Young: Study
Brett Smith for redOrbit.com - Your Universe Online
Asian elephants that give birth in their teenage years are more likely to have bigger families, but die younger than elephants that have their first child later in life, according to a new report in the Journal of Evolutionary Biology.
Based on a study of nearly 420 semi-captive Asian elephants working in the timber industry in Myanmar, European researchers found that elephants having calves prior to the age of 19 were twice as likely to die before the age of 50 as those who had their first offspring later in life. However, elephants that became mothers at a younger age had more calves after their teenage years than others that started reproducing after the age of 19.
The researchers said their work could help boost fertility in captive and semi-captive elephants, lowering the pressure on the endangered wild population.
"Understanding how maternal performance changes with age and impacts on later-life survival and fertility is important,” said study author Adam Hayward, an evolutionary ecologist at the University of Sheffield. “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.”
"As religious icons in South-east Asia and a key species of the forest ecosystem, their decline is of serious cultural and ecological concern,” he added. "Our results will enable the management of captive and semi-captive elephants to be tailored to maximize fertility, reducing strain on the wild population."
In Myanmar, about 5,000 elephants are utilized in the state-owned timber industry to offer effective travel through the dense jungle. Advocates say the approach has less impact on natural habitats since it decreases the need for roads and heavy machinery use. The work elephants are let out at night and during rest breaks – allowing them to interact and breed with wild elephants.
The researchers noted that the fertility rates are low for these elephants, meaning more elephants have to be domesticated each year.
"This is causing the wild population to decline at a rate which, it is estimated, could lead to the extinction of Asian elephants in the wild by the end of this century," Hayward told BBC News. "The Myanmar government recognizes this, and (is) keen to optimize the management of their captive elephants."
Hayward said the study is the first one to take a long-term look at the fertility of a non-human species.
"In terms of research on ageing, (we are) really interested in comparisons between humans and elephants, specifically with regard to the menopause," he said. "Female elephants can reproduce into their 60s, but female humans can't. Why not?”
"Studying aging in populations such as elephants may give insight into the evolution of aging in our own species as well as wild animals,” Hayward concluded.
"This study represents a unique analysis of the aging process in a similarly long-lived mammal,” said study author Virpi Lummaa, a biologist at the University of Sheffield. "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."