I associate big fellines with Africa or Asia: lions, tigers and leopards. Or the zoo.
Although we do have mountain lions and smaller bobcats in the Santa Cruz mountains, it is an extremely rare occurence to run into any of them. Luckily. Once, heading up to the Ridge winery, I did run into a bobcat crossing the road, recognizable by its ears. It was gone before we realized it.
Going about an hour North from the densily populated city center of Buenos Aires, along the river Plate, you run into the upscale cities of Martinez and San Isidro. Even further north, you enter the delta of the Parana river and the area of Tigre. It is frequented by the Porteños in the weekends and a popular tourist destination.
The name of this area, Tigre, struck me as odd.
This is were the English and Spanish settlers ran into the skull crushing cat of the Latin Americas: the jaguar. Locals call it tigre, and indian tribes call it Nahuel (Mapuche), Yaguareté (guaraní), Uturunco (Quechua), Overo, Manchado (Salta) and a few other names.
Both the spotted jaguar and melanistic black panther roam Argentina.
The most optimistic estimates are that there is still a population of 250 specimens in Argentina (although it is impossible to have an exact number), according to volunteer organization red yaguarete.
Since the remaining jaguars mainly roam in the North of Argentina, I do not expect to run into any. In the San Luis province, you may however see some pumas (mountain lions, or el leon as farmers call it), and el gato montes (a sort of medium sized wild cat).