Neuroscience for Kids - Drunken Elephants?

Do Wild Elephants Get Drunk?

Marula Tree
Image: Dept. Tourism of Botswana

February 21, 2006

Have you heard that wild African elephants get drunk by eating fruit? Many people believe that elephants consume alcohol by eating the marula fruit. Dr. Steve Morris and two colleagues from the University of Bristol (Bristol, United Kingdom) were skeptical of these claims and wanted to find the real story.

The scientists set out to answer three questions:

Does marula fruit contain enough alcohol to make an elephant drunk?
Do elephants really eat the fruit of the marula tree?
Can elephants get drunk eating the marula fruit?

Marula Fruit and Alcohol

The marula, a member of mango family, is a tree found in southern Africa. Although one study estimated that the fruit of the marula tree contains 7% alcohol, other studies have found that the alcohol content of the fruit is less than 1%. The alcohol content of the fruit may increase to about 3% when the fruit falls to the ground and ferments.

Marula Fruit
Image: Dept. Tourism of Botswana

Marula Fruit and Elephants

Elephants eat food that is equal to 1 to 2% of their body weight each day. In fact, most of an elephant's waking hours are spent eating. Marula fruit is one food that elephants eat.

Marula Fruit and Intoxication

The researchers estimated that 1.9 liters (0.5 gallons) of pure alcohol (ethanol) would be required to intoxicate a 3,000 kg elephant. To estimate how much marula fruit would be needed to intoxicate an elephant, the scientists assumed:

Elephants eat about 30 kg of food each day (1% body weight).
Elephants eat only marula fruit (714 individual fruits).
Each marula fruit contained 7% alcohol.
The alcohol from the fruit remained in the elephant all day.

Given these assumptions, an elephant would have to consume 27 liters (7.1 gallons) of 7% alcohol to become drunk. This volume of fluid would NOT fit into 714 marula fruits because the volume of a single fruit is only 22 ml! The only way an elephant could become drunk is if it did not drink any water, ate only marula fruit with a 3% alcohol level and ate 400% more than its normal diet. Therefore, the researchers conclude:

"... drunken elephants seem highly improbable."

The Myth of the Drunken Elephant

Wild elephants do sometimes show unusual behavior, but alcohol is unlikely to be the cause. Dr. Morris suggests that three alternative explanations for strange elephant behavior:

Elephants are poisoned by beetles that live in the bark of the marula tree.
Marula fruit contains other chemicals, such as nicotinic acid, that affects the elephants.
Aggressive behavior is normal as some elephants protect their food supply.

Did You Know?

An elephant brain weighs approximately 6,000 grams.
Elephants have a hearing range between 1 and 20,000 Hz. The very low frequency sounds are in the "infrasound" range. Humans cannot hear sounds in the infrasound range.
African elephants sleep only 3.3 hours each day. Asian elephants sleep only 3.9 hours each day.
The total surface area of the African elephant cerebral cortex is 6,300 cm². The surface area of the human cerebral cortex is 2,500 cm².
(References: Nieuwenhuys, R., Ten Donkelaar, H.J. and Nicholson, C., The Central Nervous System of Vertebrates, Vol. 3, Berlin: Springer, 1998; Peters, A. and Jones, E.G., Cerebral Cortex, New York: Plenum Press, 1984.)

Reference:
Morris, S., Humphreys, D. and Reynolds, D., Myth, Marula, and Elephant: An Assessment of Voluntary Ethanol Intoxication of the African Elephant (Loxodonta africana) Following Feeding on the Fruit of the Marula Tree (Sclerocarya birrea), Physiological and Biochemical Zoology, published electronically on February 6, 2006.

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