Horses and bulls make a bit of sense, big animals make big poos. Calling something a big poo means it is very stinky, a huge waste, etc. Very yucky. But bat poos? Those are teeny tiny, small bats make small poos. What do people have against the poos of bats?
Also, what about larger animals? Whale poos are huge, and yaks, buffalos, etc. all make big poos. Don’t ask me how I know.
Bat shit is pretty toxic, and while individual poo is small, bat colonies are absolutely massive and the shit literally piles up as up to millions of bats poop in the same place night after night.
Iirc, the phrase “bat shit crazy” comes from the harvesting of tropical bat guano (poop) for use as a fertliser. The poop is highly toxic, or contains toxic bacteria, which makes the harvesters go a little crazy! Not all bat species have this toxic poop.
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