The age of African or Asian elephants can be now estimated with high accuracy by analysing patterns of chemical changes on the DNA of blood cells. The same approach works for many other animals, including beluga whales, and could help conservation efforts.
“I’m an ageing researcher, and elephants are very interesting because they have very long lives and are cancer resistant,” says Steve Horvath at the University of California, Los Angeles. “But it is very difficult to estimate their age.”
Female elephants can live up to 75 years, and males up to 65 years. Wild elephants’ ages are often roughly estimated based on their sex and size.
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There have been attempts to develop more scientific methods based on shoulder height, tusk size and even the diameter of droppings. The most accurate method involves examining the teeth, but this cannot be done with living wild elephants.
In 2011, Horvath developed a way of estimating the biological age of people based on looking at patterns of methylation on the DNA inside cells. These patterns change over time as gene activity changes. “It still surprises me that this is even possible,” says Horvath.
This approach can also accurately age many animals including dogs, pigs and mice, Horvath has shown, though for Tasmanian devils it isn’t proving as accurate so far.
His team has now developed “ageing clocks” for elephants based on 140 blood samples from elephants at zoos in the US and Canadawhose age is known. The method is 97 per cent accurate, says Horvath.
“I think this is a fabulous technique,” says Phyllis Lee at the University of Stirling in the UK, who studies wild elephants and helped refine the tooth-based method.
But she thinks it will be of more use to biologists studying ageing than conservationists. “Knowing the age structure of populations is fantastic, but not if you have to take blood from the animals,” she says.
Lee says the method will be more useful if it can be adapted to work on elephant cells in dung samples rather than blood. This might be possible, says Horvath.
For ageing beluga whales, his team has analysed skin samples, which can be obtained from living whales using a biopsy dart.
Reference: bioRxiv, DOI:
