Golden age Why saving older animals is vital to species' survival

It's not just humans who get wiser as they age - animals do too, according to a growing body of research.

- Phoebe Weston

The bigmouth buffalo fish can reach 127 years old, the Greenland shark 392, and some sponges can live for 10,000 years or more.

And age is not just a number: as animals get older they behave differently depending on their life experiences, gain richer knowledge of their environment, and often pass it on to younger members of their group, researchers say.

The problem is, we are killing off these older creatures. "Earth's old animals are in decline," researchers warned in a paper published in Science last month, which analysed more than 9,000 peer-reviewed papers.

Few make it to old age, and the ones that do are vulnerable to being hunted or harvested by humans, because they are the biggest or have, for example, the largest antlers, horns or tusks.

Eliminating the largest and most experienced animals can have significant consequences for group culture and social structures, researchers warn, as they argue for a new approach called "longevity conservation".

Much research on ageing has focused on negative health aspects, says the lead researcher, Keller Kopf, an ecologist at Charles Darwin University in Australia.

"That simplistic idea about old individuals not being important for populations, or for environments, is really not the full story," he says.

The more he examined different groups of animals, the more he stumbled on remarkable instances demonstrating the value of older creatures.

"No matter where we looked, there were good examples," he says.

Primates, whales, elephants and pack-hunting animals all have old individuals who carry vital cultural knowledge and maintain social structures, according to the paper.