The onza may or may not be a wild cat native to Mexico. The onza is certainly a cryptid, an animal whose existence is in doubt, and whose study is the province of cryptozoologists.
The first descriptions of what could have been the onza come from the accounts of Spanish conquistadors who noted one in the enormous zoo of Montezuma, king of the Aztecs. Bernal Diaz del Castillo wrote in 1520 that among the carnivorous animals were two sorts of lion, one of them long-eared like a wolf. All of the American carnivores were new to the Spanish and they used familiar animals as points of reference. Soon afterward, in the trilingual compilation of Aztec lore called the Florentine Codex, a similar animal appears. The Aztecs called it cuitlamiztli, a Nahuatl word difficult now to translate. In the Codex it is given as “glutton cat,“ for it was said to eat all of its prey and then sleep for days. The translation “ringtail” suggests its patterned fur: “mitzli” itself referred to a puma. When the Spanish occupied and colonized the former Aztec empire, they too saw the animal in the wild and gave it the name onza.
The scarcity of accounts of the onza makes sense; if an animal is a fixture in its environment, its name suffices as a description, and there’s no need to write about its characteristics at length. During the 18th century, European missionaries new to Sonora, a Mexican state far north of the former Aztec Empire, noted the alarming presence of this big and particularly dangerous creature, but described its appearance only as much like a puma.
In 1938, a group of men hunting in the state of Sinaloa, near Sonora, shot and killed a big unusual-looking cat that local people identified as an onza; those who saw it said its ears were notably longer than a cougar’s, and the frame slimmer. Another strange cat killed in 1986 has provided the most useful evidence regarding the nature of the onza. A rancher shown the body reported that his father had shot the same kind of animal, and that it was an onza. This one was photographed: it looks like a long-legged and very thin puma. A zoologist who examined the body also performed DNA tests on it, and concluded that, though leaner and possessing retractable claws, the cat was not genetically distinct from a puma. This put to rest the notion that the onza might be a living relic of the prehistoric American cheetah.
The onza, then, may be a recurring variant of the puma. Alternatively, the thin cat killed in 1987 may not be the historical onza or cuitlamitztli at all, but an entirely different animal. Onza, from the Latin for “leopard,” is a flexible word when it comes to cats. The jaguarondi, a small and non-aggressive wild cat, is called the onza in some of the areas of its habitat. Onca, the Portuguese variant of onza, is the Brazilian word for leopard. The word is also related both to “lynx” and to an obsolete English word for the leopard, “ounce."
Castillo’s description is brief and vague, part of a long catalog of the wonders found at Montezuma’s astonishing zoo. Rather than looking at a kind of cat, he may have seen a kind of dog, perhaps even something like a hyena. This last possibility introduces another extinct species into the running: Chasmaportethes ossifragus, the only relative of the hyena in North America, an animal of the Pleistocene. It is not at all likely that this is what Castillo saw as a wolf-lion, but it is possible. Also possible is that the onza of the Spanish and the cuitlamitztli of the Aztecs, whether the same animal or not, are themselves extinct.