The pudús are the world's smallest deer, with the southern pudú being slightly larger than the northern pudú. The southern pudu has a coat which is short, glossy, and dark brown to reddish-brown in color, with slightly lighter legs and underparts. The insides of its ears and its lips are orangish. Fawns have white spots, probably for camouflage. Males have short, simple spiked antlers which are shed each year in July.
Southern pudus are natives of southwestern Argentina and southern Chile. They live between the Maule River in the north and the Chiloé province in the south. They prefer temperate rainforest with bamboo thickets and dense underbrush, as this offers good cover from predators. They will occasionally venture into more open habitats when feeding. Southern pudus occur on high mountainsides as high as 1,700 m above sea level, and also much lower down and along the coast.
Southern pudus are active during the day as well as the night. They usually rest and groom in the middle of the day, being active in the morning, late afternoon, and evening. They seem to move together when feeding, and do not form groups of more than 2 or 3. Most of the time they are sedentary, solitary, and cryptic. A pudú navigates through the thick jungle along a network of well-used trails, which lead to places for feeding and resting. They form dung piles, most of which are near resting places. Pudús are territorial animals with home range about 40-60 acres. They are wary animals and move slowly, stopping often, testing the air for predators' scent. A proficient jumper, climber and sprinter, a deer will flee in a zigzag path while being pursued
Southern pudus are browsers, and eat leaves of ferns, trees, vines, fungi, fruit, berries, herbs and shrubs. They also eat alfalfa hay, cereal, nuts, acorns, and salt.
Southern pudus are polygynous animals, which means that one male mates with multiple females. The mating season is from April to June. A female typically bears one fawn every year after gestation of about seven months. Young are precocial, born with their eyes open, and able to stand once born. The female cares for her offspring entirely on her own. Fawns are weaned when they are 2 months old, and reach full size at 3 months. They may remain with their mother for 8 to 12 months. Female pudus are sexually mature at 6 months and males at 8 to 12 months.
The main threat to this species is destruction of the temperate forest which is its habitat, for logging, cattle ranching, and other human activities. Conversion of forest to plantations and open lands poses a big threat to the survival of this species, as do hunting and road accidents. Further threats include introduced species, such as European red deer, which compete with the pudu for food. Domestic and feral dogs sometimes prey upon the southern pudu, and may also transmit parasites, to which these deer are particularly susceptible.
According to the IUCN Red List, the total Southern pudu population size is less than 10,000 animals. This species' numbers are decreasing today and it is classified as vulnerable (VU) on the IUCN Red List.
As Southern pudus are browsers and herbivores, they impact vegetation consumption, growth and abundance. They can affect the abundance of a specific species of tree, and facilitate the spread of seedlings. Southern pudus also have an important role as regards other small animals that live in the same forests, by building and maintaining tunnels in the undergrowth, which enables small animals to move through and remain hidden from predators.