By Jamie Bender
Geographic Range
Pteronura brasiliensis is endemic to South America. It is found throughout the Orinoco, Amazon, and La Plata River systems, which range from east of the Andes mountains in northern Argentina north to Venezuela and Colombia.
Carter and Rosas (1997), Emmons (1990)
Biogeographic Regions:
neotropical 
(native ).
Habitat
Pteronura brasiliensis lives in lentic freshwater rivers, lakes and creeks. On occasion, they are seen in agricultural canals and reservoirs of small dams, although they prefer gently sloped river banks and secluded areas with overhanging vegetation.
Carter and Rosas (1997), Nowak (1991)
Aquatic Biomes:
lakes and ponds; rivers and streams.
Reproduction
Reproduction in Pteronura brasiliensis is documented primarily by observations done in captivity. Peak breeding season begins in late spring and early summer, although some breeding takes place throughout the year. Females are receptive for 3-10 days of the 21 day estrous cycle. Swelling of the nipples and vulva signal receptivity. Mating occurs in the water. After fertilization, gestation ensues for 65-70 days. Birth of altricial young occurs in late August through early October.
High juvenile mortality often leads to conception of a second litter of offspring, born from December to April. Litter size ranges from 1-5 individuals (usually 2-3), each weighing approximately 170-230g. Cubs are kept in family dens for the first 2-3 weeks of life. Offspring open their eyes at 1 month and begin to regularly follow parents out of the family den. Young P. brasiliensis are weaned 3-4 months after birth. They are independent hunters and indistinguishable from their parents at 9-10 months. Sexual maturity of P. brasiliensis is reached at 2 years.
The estimated lifetime of P. brasiliensis is 10-13 years.
Carter and Rosas (1997), Gittleman (1989) , Macdonald (1984), Nowak (1991), Parker (1990), Redford and Eisenberg (1992)
Key reproductive features:
gonochoric/gonochoristic/dioecious (sexes separate); sexual .
Behavior
Pteronura brasiliensis lives in family groups of 5-8 individuals. Families have home ranges of 12 sq. km. Members of the family, which include a monogamous pair and several generations of offspring, clear an area along a streamside for living. These areas can be up to 50 sq meters and are usually located near feeding sites. Preparation of the living area includes trampling the surface vegetation, collecting tree limbs and leaves and embedding the leaves and branches into the trampled mud patch. Large burrows are then constructed under fallen logs. In addition, one to five communal latrines are placed along the site perimeter. Finally, the territory is marked by scent from the anal glands. If intruders invade the territory, parents defend it and their offspring.
Although separate territories are maintained, P. brasiliensis is a highly social mammal. Social activities include grooming, hunting, resting and communicating. Pteronura brasiliensis have 9 different vocalizations. The purposes for each of these sounds is undocumented, but vocalizations probably serve as warning signals against predators and/or contact calls.
Carter and Rosas (1997), Eisenberg (1989), Nowak (1991), Laidler (1982)
Key behaviors:
motile .
Food Habits
Pteronura brasiliensis is a piscivore. It hunts during the day, usually along river and lake margins. Hunting is done primarily by vision, but hearing, smell and touch are also well suited for murky water. Fish are captured in solitary or social hunts. Shallow water hunts take place along water edges where fish hide among vegetation. These hunts are solitary and more successful in terms of fish per individual. Deep water hunts are performed by families. Synchronous dives and organized trapping of prey against shorelines are sometimes observed.
The preferred fish diet of P. brasiliensis includes members of the catfish, perch and characin families. When fish abundance is low, P. brasiliensis feeds on crustacenas, small snakes and small caiman. Food is either taken to shore (large prey) or eaten while P. brasiliensis floats on its back (small prey). Pteronura brasiliensis takes in about 6-9 pounds of seafood per day.
Carter and Rosas (1997), Eisenberg (1989), Emmons (1990), Laidler (1982), Nowak (1991)
Economic Importance for Humans: Negative
Logging and mining workers are not able to sustain themselves on the fish/protein available in some South American river systems. P. brasiliensis and its ravenous appetite are often blamed for this lack of resource availability.
Carter and Rosas (1997), Nowak (1991)
Economic Importance for Humans: Positive
Humans continue to illegally harvest Pteronura brasiliensis for pelts. Indigenous groups use the meat and pelt of P. brasiliensis for subsistence.
Carter and Rosas (1997)
Other Comments
Pteronura brasiliensis was discovered in 1788 by Gmelin. In addition to its common name, giant otter, P. brasiliensis has also been called the Guiana flat-tailed otter, winged-tailed otter, and margin-tailed otter.
Pteronura brasiliensis moves through the water using different body parts according to its swimming speed. When swimming slowly, P. brasiliensis paddles with all four feet and leaves the tail stationary. When moving quickly, P. brasiliensis undulates its tail and leaves its feet stationary.
Pteronura brasiliensis has few predators, but occasionally it is killed by jaguars and pumas. Unattended offspring suffer greater predation due to their altricial nature. Competition also affects the livelihood of P. brasiliensis. The Neotropical otter, Lutra longicaudis, is sympatric with P. brasiliensis. Other species that are sympatric with P. brasiliensis include caimans, large piscivorous fish, and river dolphins, but competition from these species is probably minimal.
Carter and Rosas, Gittleman, Husson, Redford and Eisenberg
For More Information
Find Pteronura brasiliensis information at
Contributors
Jamie Bender (author), University of Michigan.
