Mother and Grandmother Elephants Provide Survival Benefits to Baby Animals
Only a few mammals are as long-lived as humans. One of these species is the elephant. Now, scientists have explored the lifetime reproductive patterns in African elephants in order to better understand how these creatures age and what characteristics they develop.
For long-lived species such as humans, chimpanzees, whales and some birds, longer survival is associated with higher reproductive rates and a loss in fertility only at an extremely old age. Prolonged post-reproductive lifespans may mean potential advantages for both the surviving individuals and their offspring. This means that post-reproductive longevity remains a question of major theoretical interest.
Elephant Iife histories are relatively slow. There's a 22 month gestation period followed by 12 months of nursing. In fact, calves suckle until their next sibling is born. Most elephants give birth by the age of 14.
In this latest study, the researchers looked at elephants in Amboseli National Park, Kenya. They found that most females in this region survived into their late thirties. Another 10 percent lived into their sixties. The elephants also exhibited the classical mammalian pattern of decline in reproductive rate after age 49, followed by up to 16 years of post-reproductive survival.
"The new and exciting part of our study is the strong effect females have on the reproduction of daughters and granddaughters in their family," said Phyllis Lee, one of the researchers, in a news release. "Daughters of long-lived mothers lived longer themselves and had higher reproductive rates."
While elephant calves received a major survival and reproductive benefit from having a living grandmother, the females didn't exhibit classical form of menopause. Instead, the researchers argue that elephant reproduction is a function of a long-lived mother within a successful family context.
The findings are published in the journal Behavioral Ecology and Sociobiology.
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