The fruit of the marula tree is to elephants what a triple-shot vodka lemon lime is to humans, according to wildlife lore.

But scientists say they have disproved the theory of inebriated elephants getting drunk off rotting fruit lying on the ground..

"There are traveller's tales from about 1839 reporting Zulu accounts that 'elephants gently warm their brains with fermented fruits,'" biologist Steve Morris told wildlife journal National Geographic.

But there is nothing in the biology of either the African elephant or the marula fruit to support the theory, he asserted.

"People just want to believe in drunken elephants," Mr Morris said.

The sweet, yellow fruit of the marula tree - related to the mango tree - grows widely in Africa and is used for making jam, wine, beer, and a liqueur called Amarula.

However, Mr Morris said it was unlikely an elephant would eat the fruit if it were rotten.

Elephants eat fruit directly from the tree, he explained in a study published in the journal Physiological and Biochemical Zoology in 2006.

"This a largely self-evident fact, since elephants will even push over trees to get the fruit off the tree, even when rotten fruit is on the ground."

Other experts add said that if an elephant were to eat the fruit off the ground, it wouldn't wait for the fruit to ferment.

Michelle Gadd, an African wildlife specialist with the United States Fish and Wildlife Service, said elephants were too fond of marula fruit to let it rot.

"Elephants regularly visit and revisit the same marula trees, checking the fruits and the bark for palatability and devour the fruits when they are ripe," Ms Gadd said.

Sugars in an elephant's diet were metabolised, making fermentation impossible, she said.

Scientists say a small amount of ethanol - grain alcohol - could be produced in an elephant's digestive system, but not enough to get it drunk. Through calculations of body weight and elephant digestion rates, Mr Morris said it would take nearly two litres of ethanol to make an elephant tipsy.