Depending upon the breed and the culture in which it lived,  there were different reasons to crop a dog’s ears. In some Livestock Guardian Breeds, ears were cropped to deny a predator an easy-to-reach appendage to grab hold of and bite;  The sad history of a couple of bully breeds also included cropping ears for much the same reason, only the “predator” was another dog, and the situation was a dog fight.

Cropping the ears of a Cimarrón Uruguayo was rooted in neither of those reasons (though one presumes that at one time in its history, the Cimarrón may have been used in dog fights in which case ear cropping would have been performed).  When Spanish and Portuguese conquerors abandoned their dogs as they left Uruguay, the dogs became feral. With no known predators and plenty of food “on the hoof,” the population of these dogs grew quite large. They ate off the sheep and cattle they killed, and were becoming a serious threat to settlements as packs of the dogs attacked caravans and people. By the late 18th century, authorities put bounties on the heads of these dogs, and tens of thousands of dogs were slaughtered.  Authorities paid for each dead dog, but proof of death was required, and this was typically in the form of the dog’s jaw bone or a pair of its ears. The practice would lead to ear cropping performed on newborn pups in the form of the “ear of puma.” If the practice is continued today, it’s considered by the owner to be an homage to the days when the dogs were hunted, and the ears were presented for the bounty. “Puma ears” are allowed in some breed standards, but the procedure is falling out of favor.

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