It seems animals may be drinking more than we initially thought.

In April 2024, animal control officers in Watertown, Connecticut, found two black vultures in a concerning state. The disoriented birds could barely stand and appeared to drift in and out of awareness. At a wildlife rehabilitation center, vets tested them for a range of ailments and quickly realized: these birds were intoxicated.

The vultures had managed to consume something fermented enough to cause serious inebriation, according to a Facebook post from A Place Called Hope, the rehab center. It was noted that fruit discarded in open dumpsters can ferment, leading scavengers to suffer from a lost weekend. After a classic hangover cure—rest, food, and rehydration—the birds flew off and returned to their colony.

Vultures aren’t the only animals prone to getting drunk. In Western states, tipsy grizzly bears pose a threat to trains. Waxwings, a songbird known for eating berries that can ferment, occasionally drunkenly fly into windows. In 2011, a moose in Sweden was found with its body wedged between tree branches, inebriated from fermented apples.

Building on anecdotal evidence that animals occasionally indulge in alcohol, a team of researchers from institutions in the UK, Canada, and the U.S. took on the topic in a recent study published in the journal Trends in Ecology & Evolution.

“There’s increasing evidence that humans are not the only ones ‘drinking alone,’” the researchers state, “and that many animals consume ethanol in their natural habitats.”

Nature’s Frequent Drinkers

Ethanol is the chemical term for the type of alcohol responsible for intoxication, and while there are many entertaining tales of drunk animals, the study's authors focus more on nature’s habitual drinkers. Some beetles raid beer supplies and drink it all. Vinegar flies prefer laying their larvae in fermenting fruits. Invasive green monkeys on St. Kitts are known to steal alcoholic fruit cocktails from unsuspecting tourists.

Certain fruit-eating species don’t shy away from those that are turning into natural alcoholic treats. Spider monkeys indulge in the fermented fruits of yellow mombin trees, chimpanzees consume fermented palm fruit, and Southeast Asia’s pentailed treeshrews enjoy the fermented nectar of the bertam palm.

In a food preference study, two lemur species—aye-ayes and slow lorises—were offered both alcoholic and non-alcoholic sucrose drinks. The animals could tell the difference between the spiked and non-spiked beverages, showing a clear preference for the alcoholic ones. (That 2016 study was conducted at Duke University, with a grad student tasked as the lemur bartender.)

Four Hypotheses for Animals’ Alcohol Preferences

This raises an intriguing question for researchers: Why do certain animal species choose to consume, and even prefer, alcohol—a potentially harmful substance derived from fermented yeast—especially when there’s no Budweiser commercials or high school peer pressure in the animal world?

The authors propose four potential explanations. First, the consumption may be accidental. Second, the higher sugar and caloric content in alcohol could give animals a burst of energy, stimulating their hunger-driven behaviors. Third, through evolutionary trial and error, animals may have learned that alcohol offers medicinal benefits, possibly due to antioxidants or because fermented fruits protect larvae of nectar-feeding insects from parasites.

Fourth, it simply feels good. “Ethanol can activate the endorphin (and dopamine) system, triggering feelings of relaxation and calm. This may lead to increased playfulness, exploration, social interaction, and the development of bonds, ultimately benefiting survival and reproduction,” the researchers explain.

Hey, we’ve all been there.