So, the aforementioned crucian carp makes & excretes ethanol in response to an anoxic environment, a process made feasible by the very cold water & the fish's low metabolism. That doesn't sound at
all like an air-breathing, high-metabolism, lactating mammal. So from now on, I think I'll explore the alebelly as two completely separate creatures.
I should point out that spiking one's body cells with alcohol will
not make one's flesh toxic to other creatures. Ethanol is indeed a toxin, just a rather weak one--it's simply far easier to biologically produce than other actual poisons. In addition to what's listed in
examples of animal intoxication in nature, I should point out that elephants, great apes, and some birds have been seen
intentionally getting drunk by preferentially selecting and eating overripe fruits. And if some animals can willingly get drunk for
recreation, then obviously turning oneself into a walking liquor store is hardly going to be a deterrent for them. Of course, not
all predators will exhibit that behavior; a carnivore's gut is very different from a herbivore's, and after all, if alcohol is poisonous to dogs, then it's almost certain to effect wolves the same way.
tl;dr--storing alcohol in body tissues would likely deter
some predators, but not all, and indeed might even
encourage some of them.
So, that process of storing the alcohol for future use, it could stored in a powdered or jellied form, maybe in the fat layer of the creature. If it is a high enough octane, then it also is a self-defense mechanism verse most creatures.
This would make a lot of sense, especially for the fish. Assuming the alebelly could adapt (at least some of) its cells to tolerate levels of ethanol that would be toxic in other creatures, it could store the alcohol either in the fat just underneath the skin, or the skin itself. Any creature biting the alebelly would have to get through the ethanol-laden rind first--whether the alebelly itself lives or dies, its predator would feel effects ranging from a bad taste in the mouth, to being disoriented for a while, to actual alcohol poisoning. In addition, storing ethanol just below the surface means that the alebelly could use it for
active defense: If startled by a predator, the alebelly could release some ethanol from pores in its skin, creating a cloud of water that stings a fish's gills . . . somewhat like a squid squirting ink before jetting away.
In an underground cave with zero light (even after the Light arc & cavern revamp, there would still likely be plenty of dark places), naturally animals exhibiting warning
coloration would be impossible . . . but what surface animals can do with
color, the alebelly could do with
flavor.
What organism is doing the fermenting in those fermentation sacs? Is the host or the symbiote in charge?
Like all animals, the alebelly's digestion uses microflora to do the heavy lifting: Bacteria break down what the creature eats, and excrete byproducts; the host animal itself then metabolizes those byproducts into energy. This process
already includes natural fermentation in some animals--I'm simply giving alebellies a side-stomach to provide a chamber where the food can ferment for
longer without disrupting the animal's need to eat.
I'm picturing the alebelly
mammal as something like a moose: Large, ruminant, mammalian, mostly land-based but no stranger to water either. I toyed with it being more like a manatee, but the principal draw of the animal was alcoholic milk, and can you picture dwarves
milking a manatee? The alebelly doesn't need to be as tall or muscular as a moose, or as good a natural swimmer: With the extra stomach acting as a swim bladder (even if it isn't actively producing gases through fermentation, the beast can simply just swallow air), it can devote 100% of its energy to propulsion, instead of merely staying afloat.
Further Reading:
Ethanol
can be used as a biological energy source, but only sparingly--overreliance on it leads to buildup of toxic byproducts and cell death.
https://en.wikipedia.org/wiki/Ethanol_metabolismAuto-Brewery syndrome sounds like something that might crop up in an episode of Dr. House.
Ive done something almost like this for Spellcrafts, the Root Deer which produces a sap that can be brewed into alcohol (or sugar, syrup), and its something that would fit in regions associated with magic and spheres like partying, maybe not a unique creature but a variant or randomly generated one that can be milked for alcohol.
Neat. Other possibilities: Alcoholic urine and/or musk, animals attracting mates or marking their territory with smells like whiskey or wine.