With respect to the fauna, there are 165 autochthonous vertebrates recorded: 102 birds, 11 reptiles, 9 amphibians, 33 mammals and 10 fish.

Among the species present in Lann National Park, the following are considered to possess a "special value":

Fish

Among the fish, the foreign salmonids which were sown in the past for sport purposes have pushed out autochthonous fish like the creole trout, the Patagonian pejerrey and the puyn.

Autochthonous fish
Patagonian pejerrey
Perch or criolla trout

Foreign fish
Silver or rainbow trout
Stream or fontilanis trout
Brown trout

Mammals

The pud are found in the thick areas of the wood. It is a small deer with short antlers and his body is well adapted to move in this environment. Together with the huilln, an otter endemic to Chile and Argentina, they are two of the mammals in danger of extinction which are under the protection of this National Park.

Autochthonous mammals
The most noted species are the pud, the puma, the red fox, the small gray fox, the wild monkey and other rodents. Among them, the tuco-tuco (Ctenomys maulinus), abundant in Chile, in Argentina is found only in Lann National Park. The same thing happens with the degu (Octodon bridgesi), which has only been recorded in Argentina in the region of Curruhu.
The huilln, one of the menaced species, has almost disappeared in the zone. The situation of the huemul (deer), is considered in danger of extinction, and seems to be quite critical as there are no recent recordings. However, experts have yet to complete the search in all the areas potentially suitable for this deer.
The situation of the huia cat (Felis gigna), an endemic species from the Sub-Antarctic forest has been classified as vulnerable in the country, and is uncertain.

HUIA CAT (Felis gigna)
It has long, dense and slightly woolen hair, with numerous spots closely grouped in a pale reddish-cream background. Some darker or even black specimens have also been found. It is smaller than the regular domestic cat, and it is found only in a very limited part of the Patagonian forest.

PUDU (Pudu pudu)
This species was included in the Red Book of Threatened Species, but it no longer is. There are protected communities in the South Park. It is the smallest of all the deer, between 40 and 50 cm tall and 90 cm wide. It is reddish and males differ from females in thet they show small non-branching antlers, which are renewed every year in winter.
The natural habitat of this species is the Andean forest, in particular the Valdivian Forest.

PUMA (Felis concolor)
This feline species, widely spread all over Argentina, comprises 7 sub-species. It is gray or brown, small headed, with a long and flexible body, long tail and round ears. An adult male is1.5 m long and has 35 kg. It appears in a wide range of habitats, from forests to open areas. It has mainly night habits and it is strictly carnivore, feeding on a great variety of preys.

GUANACO (Lama guanicoe)
This beautiful camel is widely spread in South America, through various habitats which include thorny scrubs, steppes, desserts, coastal areas, mountains and hills. It is the tallest land mammal in Argentina. Its hair is long, thick, and ocher, yellow or cinnamon-colored. It has big eyes, long eyelashes, moving harelips and long pointed ears. It can be 1,85 m long and 1,10 m tall including its withers. It takes its food on a great variety of plants.
Argentina is home to 96 % of all the existing guanacos in the world (about 500,000).

HUEMUL (Hippocamelus bisulcus)
This stout deer can be 1 m big at the withers. Its kind of short legs make it look shorter and fatter than other deer. The male huemul possesses branching antlers. It has thick coffee-colored hair, which turns lighter in summer and becomes yellowish-gray. Its ears and tail are over 20 cm long. It lives in mountainous wooded land and in higher places in the summer. It is a clearly territorial herbivore, a lonely animal, if any. It is rarely seen in family groups.

WILD MONKEY (Dromiciops australis)
As a matter of fact, there are no real monkeys in these southern woods: the so-called " wild monkey" is in fact a marsupial similar to weasels, kangaroos and koala bears. The birth of its cubs takes place at an early stage since their development continues out of the mother's womb, in the marsupial pouch. It is a small weasel, 10 to 12 cm long plus a tail of a similar length. It has dense and soft hair, a pointed muzzle and sharp teeth. It lives in wet woods and stays in the holes of old trees during winter time. It is the only living member of the Microbioteridos family

Exotic mammals
Due to their wide distribution it is worth adding the European hare, the wild boar and the red deer. Recently the European rabbit and the North American mink have been included and are spreading real fast.

Regarding native birds, there is a wide variety of Andean Patagonian species. Among the indigenous species belonging to aquatic environments, it is of some value to mention the presence of the torrent duck (Merganetta armata), which in the country is considered "rare". Other significant bird communities are: Magellanic woodpeckers (Campephilus magellanicus), Chilean pigeons (Columba araucana), ochre-flanked tapaculos (Eugralla paradoxa) and condors (Vultur gryphus), etc.

Among reptiles, several species of lizards are very common in the region, such as the green- headed species (Liolaemus chilensis) and the orange-bellied one (Liolaemus pictus), which are distributed all through the park area. Likewise, in the north zone of the Park, the iridescent lizard (Liolaemus tenuis) is established; registered also in Chile and in the center-west Andean region of Neuqun.

With regard to native fish, there are the creole trout or perch, the Patagonian pejerrey, the puyn and the "velvety catfish". Before the opening of the National Park, the main lakes and rivers had been sown -for sport purposes- with European or american species such as the rainbow trout, the brown trout and the stream trout. In all the river basins there are macro-invertebrates such as freshwater crabs and prawns which plays a relevant role in these ecosystems.

RED DEER (Cervus elaphus)
It is an exotic species brought from Europe. Due to its acute smell and hearing, its hunting presents many difficulties. That is why it is a favorite prey for hunters, who consider males' antlers as a valuable trophy. It lives mainly in high mountainous forested regions. It has reddish hair and highly branched antlers, which are lost to be renewed every year. During the rut, the males' necks look more hairy and swollen, as they get ready to mate with more than one female.

WILD BOAR (Sus scrofa)
It is a wild type of pig of Eurasian origin and introduced in our country. It has grayish-black hair and a long face. Males have outstanding curved tusks. The wild boar lives in herds, found in wooded and shallow lands. Due to its survival aptitude, its high reproduction rate and its omnivorous eating ways, it is difficult to control the size of its population.