From the zoogeographical point of view, Argentina currently represents a part of the neo-tropical region; the territory of NE. it belongs, up to the Paraná and Plata basin, to the Guayano-Brazilian sub-region and the rest of the country to the Patagonian sub-region. The limits of this division do not appear very clear, and undoubtedly vary over time, at least for many species; thus the jaguar or American tiger, which less than a century ago reached the Río Negro, is currently found only in the extreme north of the republic, while the guanaco is retreating more and more towards the south, which proves that the civilization factor should be counted among the main causes of these changes. The NE part. of the country constitutes a fauna area in itself, with a fauna similar to that of Brazil: to this belong monkeys, tapirs, jaguars, toucans, boas and caimans; the sub-tropical or woodland zone. In the rest of the territory it is easy to distinguish three other areas: that of the pampas, which extends south of the previous one, up to the Río Negro; the desert area, which includes Patagonia and Tierra del Fuego; and the Andean or puna area which includes the mountainous region of the Andes chain. Although these three zones seem to have a superficial similarity that markedly distinguishes them from the sub-tropical region, each of them has its own characteristics, with particular animal forms, which, in a certain way, serve to define them; so, the the desert area, which includes Patagonia and Tierra del Fuego; and the Andean or puna area which includes the mountainous region of the Andes chain. Although these three zones seem to have a superficial similarity that markedly distinguishes them from the sub-tropical region, each of them has its own characteristics, with particular animal forms, which, in a certain way, serve to define them; so, the the desert area, which includes Patagonia and Tierra del Fuego; and the Andean or puna area which includes the mountainous region of the Andes chain. Although these three zones seem to have a superficial similarity that markedly distinguishes them from the sub-tropical region, each of them has its own characteristics, with particular animal forms, which, in a certain way, serve to define them; so, the viscacha, the American flandú or ostrich and the chajá (Chauna) give the pampas their faunal character; the vicuna, the chinchilla and the cóndor are species typical of the Andean area, and the guanaco, the small ostrich, and the Magellanic goose are eminently Patagonian types.
As far as mammals are concerned, the Argentine fauna is, considered as a whole, especially rich in hedgehog and toothless rodents. Among the former we mention some very characteristic types, such as the chinchillas, viscachas and carpinchos(Hydrochoerus), the mará or Patagonian hare (Dolichotis) and the improperly called nutrias (Myocastor). The living quantity in this region can be made evident by the fact that only one genus (Ctenomys) is represented in the various parts of Argentina by 33 different species that the Argentines call with the onomatopoeic name of tuco – tucos. Among the Toothless, except for the perezoso and the anteaters found in the far north woods, the others belong to the group of armadillos or tatú, in which group are included numerous species of different sizes and various aspects, from the tatú carreta (Prionodon giganteus), more than one and a half meters in total length, up to the small pichi – ciego (Chlamydophorus truncatus) , no larger than a mouse.
In Argentina there are various marsupials of the Didelfidae family known as comadrejas, of which one of the most common is the comadreja colorada (Lutreolina crassicaudata). The smallest known species belongs to this group, the Marmosa Bruchi. Chiroptera are not as well represented as in other countries of America, but in any case they boast some species, belonging above all to the family of Molosser bats (Eumops, Nyctinomus) and to the genus Hystiotus, which is distinguished by its huge ears. The vampire (Desmodus rotundus), which reaches north as far as Mexico, has as its southern limit of its vast area of diffusion the sub-tropical zone of Argentina, where the naturalist Azara studied his habits, denying, for the first time, the absurd fables that on this chiroptera the ancient travelers had propelled. Three species of monkeys live in the woods of this region, the carayá (Alouata caraya), the caí (Cebus paraguayanus) and the miriquiná(Aotus Azarae) all three discovered by Azara himself, and which contribute to giving it an almost faunal character. tropical.
The great beasts are represented by the jaguar which retreats more and more towards the north, and by the puma which lives all over the country and which although it attacks livestock, is not dangerous for humans. The red wolf or aguará – guazú (Chrysocyon brachyurus) which lives in the sub-tropical zone, of considerable size, attacks only small mammals. The Argentine fauna also includes various species of foxes and wild cats, as well as skunks of the genus Conepatus, commonly called zorrinos, and whose pestilential smell has become proverbial. In Patagonia and in the southern part of the province of Buenos Aires lives a species of small ferret which represents a characteristic genus of this fauna (Lyncodon).
Of the order of the Perissodactyls, in Salta, Tucumán, Misiones and the Chaco there is the tapir, common in almost all of South America, while the cheromorphic Artiodactyls are represented by two types of peccary, that of the collar and that of the white mouth, in the same sub-tropical zone. Finally, the Ruminants have in Argentina species belonging to two families, that of the Camelids and that of the Cervids. Of the former in the mountains of the Andes lives the graceful vicuna, increasingly scarce due to the active persecution to which it is subjected, and the guanaco, the largest of the Argentine terrestrial mammals which swarms in the same area, and, above all, in Patagonia, where it is still possible. see, almost daily, herds of hundreds of individuals. They also exist in some llamas provincesand alpacas which are however, as in Peru and Bolivia, only in the state of domesticity. Among the Deer, the most notable species are in the sub-tropical zone, up to the Parana Delta, guazú – Pucu or swamp deer (Blastocerus dichotomos), in the pampas area deer or guazú – you (B. Bezoarticus) , and in the Andes the heumules, with a northern species (Hippocamelus antisiensis), and another southern (H. bisulcus).
The Argentine coasts, and especially those of Patagonia, are frequented by numerous marine mammals. Sea lions (Otaria flavescens), which South Americans call wolves, meet ships at the mouth of the Río de la Plata, but they abound above all on the deserted beaches of Chubut and Santa Cruz. The sea elephant (Mirounga leonina) is also sometimes seen and in the waters that bathe them there are frequently various species of whales and other smaller cetaceans, among which the dolphins of the genus Cephalorhynchus predominate, with white mottled skin and black.