Fun facts about Amazon rainforest’s Native Giant River Otter

Giant otters (Pteronura brasiliensis), Cuiba River, Near Porto Jofre, Pantanal, Brazil

The giant river otter (Pteronura brasiliensis) or giant otter is a South American carnivorous mammal. It is the longest current member of the weasel family, Mustelidae, a globally successful predator group, reaching up to 5.6 ft (1.7 meters). Atypical of mustelids, the giant river otter is a relatively social species, with family groups typically sustaining three to seven members. The groups are focused on a powerful breeding pair and are remarkably cooperative and cohesive. Although typically peaceful, the species is incredibly territorial, and aggression has been seen between different groups. The giant otter is diurnal, being active particularly during daylight hours. It is the loudest otter species, and distinct vocalizations have been documented that symbolize aggression, alarm, and reassurance.

Let’s explore a bit more about the Giant River Otter:

Features and Biology

The giant otter is sharply separated from other otters by behavioral and morphological characteristics. It has the most comprehensive body length of any mustelid family species, although the sea otter may be fatter. Males are between 4.9 and 5.6 ft (1.5 and 1.7 m) in length from tail to head, and females between 3.3 and 4.9 ft (1 and 1.5 m). The animal’s well-muscled tail can add an additional 28 in (70 cm ) to the total body length. Early reports suggested huge males of up to 7.9 ft (2.4 m); intense hunting likely reduced the existence of such massive specimens.

Weights are between 57 and 71 lb ( 26 and 32 kg) for males and 49 and 57 lb (22 and 26 kg) for females. The giant otter has the smallest fur of all otter species; it usually is chocolate brown but maybe fawn or reddish and seems nearly black when drenched. The fur is too dense, so much so that water cannot enter the skin.

Guard hairs trap moisture and keep the inner fur waterproof; the guard hairs are approximately one-third of an inch ( 8 millimeters) in length, nearly twice as long as the inner coat’s fur.

Its soft velvety feel makes the animal highly sought after by fur traders and has added to its decline. Unique markings of cream or white fur color the throat and below the chin, allow individuals to be recognized from birth.

Giant otters use these marks to identify one another. Upon meeting other otters, they engage in a behavior known as “periscoping,” displaying their upper chests and throats to each other.


The giant otter is a boisterous animal with a multifaceted repertoire of vocalizations. All otters produce vocalizations, but the giant otter may be the most vocal by volume and frequency. Scientists identified nine distinct sounds, with additional subdivisions possible, depending on the context. Explosive snorts or Quick hah barks suggest potential danger and immediate interest. A wavering scream may be used in blunt charges against trespassers, while a low growl is used for advancing warning. Coos and hums are more reassuring within the group. Whistles may be used as a warning of not that hostile intent between groups, although evidence is insufficient. Newborn pups cry to elicit attention, while older young wail and whine when they start to engage in group activities.

Reproduction and life cycle

Giant otters construct dens, which are holes dug into riverbanks, normally with multiple chambers inside and various entrances. They give birth inside these dens during the summer season. In Cantão State Park, otters dig their reproductive holes on the oxbow lakes’ shores starting around July, when waters are already relatively low. They give birth between July and October, and the young pups appear for the first time in November and December, which are the months of most insufficient water and fish concentrations in the dwindling channels and lakes are at their peak. This makes it more comfortable for the adults to catch sufficient fish for the growing young and for the pups to properly learn how to hunt fish. The entire group, including non-reproductive adults, usually older siblings to that year’s pups, cooperates to catch sufficient fish for the young.

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