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Pteronura brasiliensis - Giant Otter

Skull Pictures:

Dorsal    Ventral

Lateral    Dentary

Photos by Christopher Yahnke, collection of the Field Museum of Natural History

Physical Description:

With a length of 2 m. and a weight of 32 kg., Pteronura brasiliensis is the largest of all the thirteen otter species (Grzelewski 2002).  The females are slightly smaller weighing about 60 lbs.  They have a life expectancy of 12 years in the wild and 21 years in captivity (Lailder 1995). 

All aspects of Pteronura brasiliensis have been adapted for aquatic life.  On average their tail is 2 ft long.  About 2/3 of it flattened to help them maneuver while swimming.  Their chocolate brown fur is thick, dense, and water repellant.  Their head is round and their eyes are large and acute for perfect under water vision.  Their ears are small and can be closed while underwater.  Only two slit like nostrils are visible on their fully furred nose.  They have large webbed feet with sharp claws at the end of short stubby legs.  They have a unique yellowish mark on their neck that can help distinguish individuals. 


Pteronura brasiliensis is endemic to the lakes, slow-moving forested rivers, creeks, reservoirs, and swamps of South America where it is one of the largest predators (Lailder 1995).

Ontogeny and Reproduction:

Pteronura brasiliensis have a gestation period of 65-70 days, after which a litter of 1-5 pups is born. The mothers give birth annually in underground dens near the shore. The pups are taught to swim after 2 months and leave to fend for themselves after 2-3 years (Lailder 1995). Pteronura brasiliensis are very sensitive to human activity, and tourists boating too close to a nursing mother can cause her so much stress that she stops producing milk.

Ecology and Behavior:

Pteronura brasiliensis are extremely social animals and prefer to stay in familial groups (Serra-Vega 1991). They also hunt as a social group. During the day, they often groom one another, which according to scientists, promotes group unity. At night, they retire to communal dens, dug ten feet into the ground along shorelines. Usually, only one pair of giant otters breed within a pack.


Pteronura brasiliensis are nicknamed in Spanish "lobos de rio" or "the river wolves," and is the largest and most formidable otter in the world.

Literature Cited:

Grzelewski, Derek. Otterly Fascinating. Smisthsonian. 33(8):100


Laidler, K and Lailder, L. Giant Among Otters. Wildlife Conservation.  98(3):40


Serra-Vega, J. An Ecological Eldorado: Peru's Manu National Park. UNESCO Courier. 44(8/9):75


Reference written by Josh Odekirk, Biology 378 (Mammalogy), University of Wisconsin – Stevens Point.  Edited by Christopher Yahnke. Page last updated August 15, 2005.

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