Can hedgehogs get drunk from eating rotting/fermenting fruit?

Summary

Possibly, although it is more likely that the hedgehog is sick. We have seen elsewhere on the site that severe dehydration (sometime poisoning) can result in both daytime activity and a “drunken-like” staggering in hedgehogs. In effect, any hedgehog found out during the daytime, excluding a couple of hours either side of dusk, and especially those seen staggering should be taken to a rescue centre at the first available opportunity.

The details

A quick search string of “drunk animal” entered into video-sharing websites will bring up home videos of many different species, from domestic dogs and cats to warthogs, squirrels and elephants, acting in a way construed as being “drunken”. These are, of course, people’s interpretation of what is happening, but there are reports in the scientific literature telling of animals exhibiting symptoms we typically associate with having drunk too much alcohol.

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When over ripe, palm fruit can have an alcohol content approaching 5%. - Credit: Hafiz Issadeen

So what is alcohol? Chemically, an alcohol is any organic molecule where a carbon (C) atom is bound to a hydroxyl group (an oxygen (O) atom bound to a hydrogen (H) atom) – they form a molecule with the chemical formula C-OH. In most circles, the term “alcohol” refers to ethyl alcohol, more commonly called ethanol. Ethanol is produced by the fermentation of sugars; basically, during the process of metabolizing sugars in the absence of oxygen, some microorganisms (particularly yeasts) produce ethanol and carbon dioxide. During this process, the lack of oxygen is important. If oxygen is present the yeast use it to produce carbon dioxide and water instead.

As fallen fruit start to decompose, microorganisms start to convert the sugars into ethanol. Ethanol concentrations in most fruits and berries are very low, typically at less than 1%. Nonetheless, in a 2004 paper to Integrative and Comparative Biology, Robert Dudley noted that the pulp of overripe palm fruits (Astrocaryum standleyanum) may have an alcohol content as high as 4.5%. Similarly, fruit that has been decomposing in warm conditions may have a higher ethanol content, although ethanol can prevent yeast growth at certain concentrations, meaning ethanol production is self-limiting.

When alcohol enters the bloodstream more quickly than the liver can break it down, the subject suffers from alcohol intoxication or, more colloquially, drunkenness. The effects of alcohol on the body are complex, far out of the scope of this article, but sufficed to say that it acts on nerve receptors and certain proteins, causing lethargy, poor coordination and, at its most extreme, respiratory failure and death. An individual’s susceptibility to alcohol is influenced by a variety of factors, particularly past exposure (regular drinkers show fewer effects than occasional drinkers); but, because the breakdown of alcohol in the body is controlled by enzymes, an animal’s genes also play a role. In other words, it is very difficult to predict how a certain concentration or amount of ethanol will affect an individual.

Of drunken hedge-pigs

There are a couple of passing comments in the literature about apparently drunk hedgehogs, but I have yet to come across any empirical evidence from the wild. In hedgehogs, severe dehydration causes similar incoordination and lethargy to intoxication and it seems likely the two conditions may have been frequently confused in the past. I’m aware of only one report that provides some tentative evidence for drunk hedgehogs; it comes from wildlife photographer and naturalist Roger Powley on the Isle of Wight. The following is the crux of his recollection.

Windfall apples rotting on the ground attract numerous insects during the autumn and this may also attract hedgehogs. Whether hedgehogs can become drunk feeding on either the fermenting fruit or the insects remains unclear. - Credit: Tim Parkinson

During the summer of 1996 we had masses of apple and pear windfall from our fruit trees, which we dumped down the back of the garden near a compost heap. We were used to hedgehogs being in the garden and we frequently saw tunnels leading into the heap, where we presumed the hedgehogs spent the winter in hibernation. That year, we found hedgehogs wandering ‘drunk’ around the garden during the day. They allowed their photos to be taken and seemed otherwise healthy (not obviously emaciated or sick). One was found curled up on the lawn during daylight, while another had to be rescued from the pond during the day.

In all previous (and subsequent) years, when the windfall wasn’t present in such quantities, the hedgehogs had been entirely nocturnal and, if found sleeping, they were in the flower beds or bushes and never out in the open. The fruit showed signs of having been chewed and smelt strongly of ethanol; that said, we never actually saw any hedgehogs eating it.

Knowing Roger, I can attest that he is not prone to misappropriation or exaggeration and aspects of his report, particularly that hedgehogs were found curled up asleep in the middle of the lawn, imply dehydration was unlikely to be the cause. This nonetheless remains only circumstantial evidence for drunkenness and I would be interested to hear from anyone with empirical data of alcohol intoxication in hedgehogs.

(Note: The first action upon finding a hedgehog that looks drunk is to seek veterinary attention, because it is likely to be severely dehydrated.)