There seems to be a pretty popular story (I most recently saw it today on Cracked.com, not always the most reliable history source) that goes something like this: "Because of their Medieval superstitious, people in the Middle Ages thought cats were allied with the devil, and killed them in huge numbers, thus indirectly leading to the Black Plague due to there being no cats to kill the disease-spreading rats."
This story seems kind of fishy to me, as I've never heard any actual evidence for it, and as there seem to be plenty of cats in Europe today. Is there any actual evidence that this happened?
This may be a reference to an episode developed by Richard Darnton in The Great Cat Massacre (1985). The incident occurred in France in the 1730s and was apparently a worker's rebellion, which focused on the pampered cats of the affluent who employed people under substandard conditions.
Cats, like many animals including rabbits, could be regarded as familiars for witches. Any animal under suspicious circumstance could be regarded as potentially guilty, and could be "punished" accordingly, but cats were valuable in pest control, so systematic killings would be counter intuitional. Darton's popular book - with its sensational title - put forward the idea of these sorts of incidents, probably extending the notion of cat killings beyond what occurred in reality.
The Valencian consulate became particularly famous because its highly comprehensive law-code was printed in the city in 1494, and was widely diffused. The code addressed age-old problems in maritime law:
If any property or merchandise is damaged by rats while aboard a vessel, and the patron had failed to provide a cat to protect it from rats, he shall pay the damage; however, it was not explained what will happen if there were cats aboard the vessel while it was being loaded, but during the journey these cats died and the rats damaged the cargo before the vessel reached a port where the patron of the vessel could purchase additional cats. If the patron of the vessel purchases and puts aboard cats at the first port of call where such cats can be purchased, he cannot be held responsible for the damages since this did not happen owing to any negligence on his part.
Abulafia, The Great Sea, p. 565 who in turn attributes it to Jados, Consulate of the Sea, p. 38; also pp. 35–8, 54–7, 204–8
Not knowledgeable to make any judgement, hopefully the source still serves to shed some light on the situation.
There does seem to be some actual research to prove this: Killing of Cats in the Medieval Period: an unusual period in the history of Cambridge https://www.academia.edu/1061079/LUFF_R._M._MORENO-GARCIA_M.1995._Killing_cats_in_the_Medieval_Period._An_unusual_episode_in_the_history_of_Cambridge_England._Archaeofauna_4_93-114