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The Giant Otter

The Giant Otter

The “Giant Otter Project” was founded with the objective of strengthening the conservation of the species and its ecosystem, seeking to improve human coexistence with the giant otter and the engagement of stakeholders in conservation actions and decisions

The species

The giant otter belongs to the otter subfamily (Lutrinae) and is the largest of the 13 extant otter species.
The scientific name of the otter is Pteronura brasiliensis (Ptero = wing, nura = tail), due to the flattened shape of its tail, which resembles a wing or an oar. The first giant otter was discovered in Brazil, which is why its scientific name is also a tribute to the country, which still has the largest distribution area of the species.
Otters only occur in South America and feed mainly on fish, but they can also consume crabs, frogs, snakes, lizards, caimans and other vertebrates.

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Giant otters live in groups of 2 to 20 individuals, consisting of a breeding pair and several young individuals of different ages, who help in raising the small cubs.
Their dens are built along the banks of rivers and bays and are used for protection, resting, reproduction and care of the young.

In addition, the group uses latrines, which are a kind of collective bathroom, which serves to mark the territory with its characteristic smell.
The territories of the groups measure a linear average of 10 km along water bodies and the banks are scent-marked daily by the members of the group. During the rainy season, when the level of the river rises, territories can increase up to 3 times or more.
Scent-marking is one of the ways that giant otters communicate and that helps groups to organize the limits of their territories along the water bodies.
Encounters between rival groups often end in violent and noisy fights.

Otters use a vocal repertoire with up to 15 different sounds to communicate.

To learn more about the species, read our publications.

Threats

Giant otters are considered globally endangered (IUCN Red List) and need your help.

Until the beginning of the 1990s, hunting for the commercialization of pelts drastically reduced the population of giant otters along all the species distribution. In Brazil, viable populations of the species occur in some regions of the Amazon Basin and in the Pantanal. In the Cerrado, a giant otter population seems to be limited to the Tocantins River basin.
The Pantanal population is at the southern limit of the species’ distribution and, in addition, has the lowest genetic diversity.

Habitat loss and degradation, mainly due to human activities is today the greatest threat to the species. Throughout their entire range, giant otter populations are being decimated by contamination of rivers and destruction of riparian forest caused by gold mining, agriculture and other human activities. Hydroelectric dams can isolate populations and degrade the environment, changing the availability of resources. Human conflicts with the species are also common and are often motivated by the simplistic idea that the species is dangerous or a competitor for fish.
Poorly-managed tourism is also a threat. Traffic and the approach of vessels can scare away the group or even affect the survival of cubs.

Behaviors and Sounds

Have the experience of hearing some of the sounds of giant otters.

Cub care / Sounds: hum’s, coo’s, pur’s and high-pitched coo’s

In a group of giant otters, only the dominant pair reproduces, but all other individuals help in the care of the offspring. After the third week of life, the adults begin to carry the cubs out of the den, to receive their first baths and swimming lessons. Some adults are clumsier than others, but this learning is critical to the success of cubs. During activities, it is common to hear pur’s and discreet hum’s, interspersed with high-pitched coo’s vocalized by adults, which can intensify if the cubs do not obey. Cubs, in turn, whimper and vocalize high-pitched squeaks during baths. But it’s during the fishing lesson that the adults have the harder work, especially when the litter is hungry. Cubs receive small and alive fish near the shores to learn how to capture them, but the capture is not always successful and the cubs vocalizes even more strident screams until it satiates its hunger.

Food defense / Sound: growl

Despite performing most of the activities together, giant otters do not share their food with the other members of the group. When an otter approaches another, who is devouring a delicious fish, it will hear an intimidating growl that can get louder and louder if he continues to approach.

Agonism, fight / Sound: snorts, high-pitched screams and calls

When an intruding individual or group of giant otters is detected by the resident group, a dispute can ensue. It’s what biologists call an “agonistic encounter,” and it can take the form of long chases and even violent physical confrontations, accompanied by a chorus of screams and high-pitched calls, interspersed with snorts. Giant otters can be seriously injured in these fights and some can even die from their injuries.

Scent-Marking: purring and humming

Giant otters are territorial, what means that they defend the stretch of river where they live with determination. The groups patrol their territory daily and choose specific places along the banks to leave their scent and to signal their property to other giant otter intruders. During territory demarcation, all individuals defecate and urinate in latrines (collective toilets located on the banks), purring while spreading the smell around the place. The purring can intensify and be interspersed with more acute sounds such as “hum’s” and “high-pitched coo’s”, which are even louder.

Call/Sound: adult call

The giant otter group is very cohesive, what means that the members of the group perform almost all activities together. When an individual moves away from the group and feels lost, it vocalizes with high-pitched screams or “adult calls” , calling the others.