By Helen Briggs
Science reporter, BBC News
Elephants keep track on up to 30 absent relatives by sniffing out their scent and building up a mental map of where they are, research suggests.
Elephants can identify individuals from the scent of urine
Herd members use their good memory and keen sense of smell to stay in touch as they travel in large groups, according to a study of wild elephants in Kenya.
The University of St Andrews studied 36 family groups of elephants living in Amboseli National Park.
The research is published in the Royal Society journal, Biology Letters.
Wild elephants form matriarchal family groups which travel, forage for food, and socialise together. Individuals need to keep track of each other, as family members split up into smaller groups or overtake companions as they wander the home range.
Psychologists from the University of St Andrews collected samples of female elephant urine from the ground and presented it to relatives to trick them into believing that the elephant had recently passed by.
Elephants showed surprise when they encountered the scent of an individual who was actually walking behind them so could not possibly have been there.
"We reckoned that only if each elephant was continually updating its memory of where everyone was, and was able to identify specific individuals from their urine, would they show any different reaction to this case," said co-researcher Dr Lucy Bates.
The elephants also reacted when the urine was from a family member who was far away, and not supposed to be in the area.
Dr Byrne said it is hard enough for humans to keep tabs on each other, let alone elephants, which have poor day vision.
Dr Bates collects samples for the experiments
"If you think of a comparable human situation - perhaps a mum in the supermarket with three kids and a husband who'd rather be looking in the DIY section - keeping track of four or five people is really quite a strain," he told BBC News.
"But our elephants are doing it in parties of 20 to 30 family members."
But Dr Byrne said that elephants have two advantages over humans - their excellent sense of smell and, if their popular reputation is anything to go by, a good memory.
"It may be that where elephants really excel in memory is not remembering things for very long periods but in everyday working memory - where it is important to update and delete things rather than remember things forever," he added.
The research was carried out with members of the Amboseli Trust for Elephants.