Drunken Monkeys! Booze-loving primates proven to seek out high-alcohol nectar

Some primates actively seek out the booziest treats they can find, and tolerance to alcohol may even have given a few species an evolutionary edge over their lightweight cousins, according to a new study.

In tests conducted by researchers at Dartmouth College in Hanover, New Hampshire, aye-ayes, a little loopy looking lemur species from Madagascar, and the slow loris, a small Ewok-esque primate with enormous eyes from Southeast Asia, both exhibited a clear preference for fake nectar laced with higher doses of alcohol.

As Robert Dudley, author of the The Drunken Monkey, has documented, animals such as chimps have been observed getting hammered on fermented nectar in the wild before, but scientists have been unclear about whether this behaviour is deliberate or random. This new study—conducted on captive animals and reported in New Scientist—appears to confirm that some species do indeed have a pronounced preference for boozy juice, and the stronger the better.

The slow loris commonly quaffs bertam palm nectar, which can naturally attain an alcohol concentration of up to 3.8% per cent, and aye-ayes, who typically feast on beetle larvae ripped from rotting wood with their ET-like extended middle finger, also spend about a fifth of the wet season supping nectar from the traveller’s palm, an elixir thought to occasionally be fermented by natural yeasts introduced to the mix by pollinating insects.

Pie-eyed primates: there's a reason the loris (above) is slow, and the aye-aye has red eye eyes
Pie-eyed primates: there’s a reason the loris (above) is slow, and the aye-aye has red eye eyes

The study focussed on the selections repeatedly made by two aye-ayes and one slow loris in controlled conditions. When offered a choice of water or a graded mix of sugary water and alcohol (akin to the mix found in flowers) ranging between 0% and 5% alcohol for the aye-ayes and 0% and 4% alcohol for the loris, the animals gravitated to the strong stuff, supping twice as much of the more boozy juice.

‘Aye-ayes used their fingers to compulsively probe the cups long after the contents were emptied, suggesting that they were extremely eager to collect all residual traces,’ reported Nathaniel Dominy, one of the study’s authors.

And according to Samuel Gochman, also from Dartmouth College, primates that like alcohol have a distinct advantage when seeking sustenance, because alcohol forms vapours easily, helping the animals locate edible fruits and flowers.

Matthew Carrigan from Santa Fe College in Florida, says it’s possible the boozy beasts also get a dietary benefit from consuming alcoholic nectar, with the drug slowing down the metabolism and promoting fat storage.

Aye-ayes possess a highly functioning version of an enzyme called alcohol dehydrogenase, which enables them to detoxify booze. The last common ancestor of humans, chimps and gorillas also independently evolved this enzyme, probably—according to Carrigan—around the time that primates began walking on the ground and munching on overripe fruit.

And this all fits in neatly with Dudley’s drunken monkey theory, which speculates that primate species who could cope with alcohol had an evolutionary edge over those who couldn’t—an argument that goes some way to explaining why humans across almost all continents and cultures have developed and abused alcoholic drinks.

But remember people (and primates), while booze may have helped you evolve, it can also lull you into over estimating your ability to dance, sing, and fight, all of which can retard your chances of passing on your genes. Always drink nectar responsibly.

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