Pteronura brasiliensis
Giant River Otter
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.
Distribution
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.
Remarks
Pteronura brasiliensis are nicknamed in Spanish "lobos de rio" or "the river
wolves," and is the largest and most formidable otter in the world.
References
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.