Drunk birds: inebriation in the wild
Humans are not the only animals who like getting drunk. Plenty of birds and mammals get tipsy on natural brews.
DR STEPHEN Cutter's is used to riding out the drunken parrot season before the rains each year, when scores of intoxicated red-collared lorikeets (Trichoglossus rubritorquis) are picked up off Darwin's streets and brought to the Ark Animal Hospital in Palmerston.
"People find them huddled in a corner or at the bottom of a tree. Mostly they just look sick - just a sad little bundle of feathers hiding from the world," Stephen says. "They tend to be depressed, they can't fly, and they have difficulty climbing or balancing on perches."
In northern Australia, mango, umbrella, and other trees, can cause mild drunkenness in birds when the fruit or nectar ferments at different times throughout the year. But many of the lorikeets brought to the hospital aren't just mildly drunk - they're completely sloshed, and sometimes for days at a time.
The most probable culprit is the Schotia brachypetala, a southern African native, commonly known as the drunken parrot tree. Stephen says he's seen this species pop up in gardens all over Darwin in recent years, and its rapid rise to abundance may be taking its toll on the birds.
Drunk animals can't help their problem
Birds aren't experienced drinkers - unlike humans, they don't drink to get drunk.
"They don't want to ingest a lot of alcohol, but they're probably just being forced into the situation because there's not a lot of fruit available to them," says Dr Glen Chilton, ornithologist at James Cook University, Townsville.
Fruit-eating birds are particularly vulnerable because they depend so heavily on a food source that ferments, and to get enough proteins they need to eat a lot of it.
Glen says if the lorikeets in Darwin appear to be getting drunk on a larger scale, it is probably related to the limited supply of ripe fruit, a challenge that isn't unique to Australian birds.
In the northern hemisphere, heavy winter snows make it very difficult for birds to find fruit, and the rotting varieties that emerge once the snow starts to thaw - blackberries, hawthorn berries, juniper berries, crab apples - can produce very toxic levels of ethanol as the natural sugars ferment.
In the United States, robins, waxwings and starlings have been found dead in large flocks after eating toxic berries and diving into the ground or colliding with solid structures. In Vienna, Austria, 40 songbirds were found with broken necks and damaged livers after eating fermented berries and flying into windows.
Drunk animals like to party
Fermented fruits are not a first choice for many birds, but other animals would give anything to get their dose. (See a list of 10 animals known to get intoxicated)
"There's plenty of evidence that orangutans, and apes and elephants will wonder for miles to seek the pleasure of fermented fruits; so they basically like to get drunk," says Professor Gisela Kaplan, an expert in animal behaviour at the University of New England in Armidale.
The drawback for these keen drinkers is that happy hour only comes around at certain times during the year. "The opportunity to be inebriated is limited in animals, simply because they have to wait for the natural processes to occur," says Gisela. "They can't just go to a store and ask 365 days a year."
So when the fruits are overripe, the party animals make the most of it. Gisela says orang-utans in Borneo binge on the Durian fruit, which produces a very strong alcohol when it ferments. While in Africa, elephants and monkeys have been reported - though anecdotally - getting tipsy on the fermenting fruit of palm trees and the Marula tree.
In Sweden just last month, an intoxicated moose made international headlines when it became entangled in an apple tree in a residential area after gorging on the fermented fruit. But while animals seem to enjoy behaving badly under the influence, the phenomenon is seldom studied.
Even if alcohol isn't physically harmful to birds, it does make them vulnerable in other ways. When birds are drunk they lose mobility, making them helpless in the presence of predators. And if they can manage to fly while under the influence, their lack of coordination may have devastating consequences, much like those affecting humans who drink and drive.
"We know that [drunkenness] doesn't have serious side effects on mammals," says Gisela. "Mammals just sleep it off, but we have little knowledge of how birds deal with it."