Teen Elephant Moms Die Younger But Have Larger Families

Among Asian elephants, teen moms die young but grow up to have larger families, according to a new study by University of Sheffield biologists.

Writing in the Journal of Evolutionary Biology, the researchers detail their study of 416 semi-captive Asian elephants in Myanmar, reporting that elephants that had their first calf before the age of 19 were almost twice as likely to die before the age of 50 than elephants that had their first offspring later in life.

Elephants have remarkably long gestation periods. The Asian elephant has an average gestation of 645 days, and the interval between periods of birth typically lasts two years, therefore, a young mother elephant has more opportunities to give birth than an elephant that does not become pregnant until later in life.

Interestingly, the researchers found that an Asian elephant that gives birth twice in her teenage years will have calves with a greater likelihood of surviving to independence than those born to mothers after the age of 19.

However, doing so comes at the cost of a shorter lifespan, the researchers report. Asian elephants can live into their 70s, so one that dies in its 50s is a life cut short. The researchers report that this is in essence a natural selection gamble. Mother elephants will risk cutting their own lives short by reproducing early in life in order to ensure the survival of their young.

The researchers report that their work will help with elephant conservation efforts.

"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 Adam Hayward of University of Sheffield's Department of Animal and Plant Sciences.

"Our results will enable the management of captive and semi-captive elephants to be tailored to maximize fertility, reducing strain on the wild population," he said.