Pteronura brasiliensisgiant otter

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)


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

Physical Description

  • Average mass
    24000 g
    845.81 oz


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
  • Average number of offspring
  • Average gestation period
    68 days
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    730 days



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)

Communication and Perception

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: 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)

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)

Conservation Status

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


Jamie Bender (author), University of Michigan-Ann Arbor.



living in the southern part of the New World. In other words, Central and South America.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


reproduction that includes combining the genetic contribution of two individuals, a male and a female


uses touch to communicate


Carter, S.K. and F.C.W. Rosas. 1997. Biology and conservation of the Giant Otter, Pteronura brasiliensis. Mammal Review 27(1):1-26.

Chanin, P. 1985. The Natural History of Otters. Facts on File Publications, New York.

Eisenberg, J.F. 1989. Mammals of the Neotropics. Volume 1. University of Chicago Press, Chicago.

Emmons, L.H. 1990. Neotropical Rainforest Mammals: A Field Guide. University of Chicago Press, Chicago.

Gittleman, J.L. 1989. Carnivore Behavior, Ecology and Evolution. Cornell University Press, Ithaca.

Husson, A.M. 1978. The Mammals of Suriname. Leiden Publishing, Netherlands.

Laidler, L. 1982. Bring back the giant. New Scientist 23:825-828.

Macdonald, D. 1984. Encyclopedia of Mammals. Facts on File Publications, New York.

Nowak, R.M. 1991. Walker's Mammals of the World. John Hopkins University Press, Baltimore.

Parker, S.P. 1990. Grzimek's Encyclopedia of Mammals. Volume 3. McGraw-Hill Publishing Company, New York.

Redford, K.H. and J.F. Eisenberg. 1992. Mammals of the Neotropics: the South Cone. University of Chicago Press, Chicago.