Lobo de Rio (the River wolf), Los Lobos del Rio (Wolves of the River), Ariranha, Giant river otter
The Giant otter (Pteronura brasiliensis) is a South American carnivorous mammal. It is the longest member of the weasel family, Mustelidae, a globally successful group of predators. The Giant otter has no serious natural predators other than humans, although it must compete with other predators, such as the Neotropical otter, jaguar, and various crocodilian species, for food resources.
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DiurnalDiurnal animals are active during the daytime, with a period of sleeping or other inactivity at night. The timing of activity by an animal depends ...
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CarnivoreA carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of a...
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PiscivoresA piscivore is a carnivorous animal that eats primarily fish. Piscivorous is equivalent to the Greek-derived word ichthyophagous. Fish were the die...
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SemiaquaticSemiaquatic animals are those that are primarily or partly terrestrial but that spend a large amount of time swimming or otherwise occupied in wate...
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AltricialAltricial animals are those species whose newly hatched or born young are relatively immobile. They lack hair or down, are not able to obtain food ...
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ViviparousAmong animals, viviparity is the development of the embryo inside the body of the parent. The term 'viviparity' and its adjective form 'viviparous'...
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TerritorialA territory is a sociographical area that which an animal consistently defends against the conspecific competition (or, occasionally, against anima...
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Apex predatorAn apex predator, also known as a top predator, is a predator at the top of a food chain and has no natural predators. These animals usually occup...
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Pursuit predatorPursuit predation is a form of predation in which predators actively give chase to their prey, either solitarily or as a group. Pursuit predators r...
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MonogamyMonogamy is a form of relationship in which both the male and the female has only one partner. This pair may cohabitate in an area or territory for...
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Highly socialHighly social animals are those which are highly interactive with other members of their species. They live in large groups, nest in colonies, and ...
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Dominance hierarchyA dominance hierarchy (formerly and colloquially called a pecking order) is a type of social hierarchy that arises when members of animal social gr...
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Not a migrantAnimals that do not make seasonal movements and stay in their native home ranges all year round are called not migrants or residents.
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starts withThe Giant otter is clearly distinguished from other otters by morphological and behavioral characteristics. It has the greatest body length of any species in the mustelid family. The Giant otter has the shortest fur of all otter species; it is typically chocolate brown but may be reddish or fawn, and appears nearly black when wet. The fur is extremely dense, so much so that water cannot penetrate the skin. Guard hairs trap water and keep the inner fur dry; the guard hairs are approximately 8 millimeters (one-third of an inch) in length, about twice as long as the fur of the inner coat. Its velvety feel makes the animal highly sought after by fur traders and has contributed to its decline. Unique markings of white or cream fur color the throat and under the chin, allowing individuals to be identified from birth. Giant otter muzzles are short and sloping and give the head a ball-shaped appearance. Their ears are small and rounded. The nose (or rhinarium) is completely covered in fur, with only the two slit-like nostrils visible. The Giant otter's highly sensitive whiskers (vibrissae) allow the animal to track changes in water pressure and currents, which aids in detecting prey. The legs are short and stubby and end in large webbed feet tipped with sharp claws. Well suited for aquatic life, it can close its ears and nose while underwater.
This species is a native of South America (except for Chile), east of the Andes. Currently, there are almost none in Argentina and Uruguay, and they are very rare in Paraguay. They are seen within the Amazon, Orinoco, and La Plata River systems and are found in slow-moving streams and rivers, lakes, swamps, and marshes, as well as flooded forests during the rainy season. Giant otters prefer habitats with non-floodable banks that have vegetation cover and where there is easy access to hunting places in relatively shallow waters.
Giant otters are diurnal highly social animals; they live together in family groups numbering 2-20 individuals. A family has a home range of 12 sq. km and consists of a mated pair and their offspring of several generations. The family members clear an area beside a stream for their living quarters, of up to 50 sq meters, usually near feeding sites. Sizeable burrows are then built under fallen logs. One to five latrines for communal use are placed along the perimeter of the site. The established territory is then marked by the scent from the animals' anal glands. If intruders invade the family's territory, the parents will defend it and their family members. Within groups, otters are extremely peaceful and cooperative. They groom each other, rest, and may even hunt together. Giant otters are especially noisy and have a complex repertoire of vocalizations. Quick ‘hah’ barks or explosive snorts suggest immediate interest and possible danger. A wavering scream may be used in bluff charges against intruders, while a low growl is used for aggressive warning. They will also make hums and coos, and whistles. Newborn pups squeak to elicit attention, while older young whine and wail when they begin to participate in group activities.
Giant otters are strictly carnivorous (piscivorous) and mainly fish such as cichlids, perch, characins (such as piranha), and catfish. If fish are unavailable, they will also take crabs, snakes, and even small caimans and anacondas.
This species is monogamous, and pairs stay together for life. Reproductive behavior has largely been documented by observations of captive animals. Although some breeding occurs throughout the year, the peak of the breeding season is from late spring to early summer. Gestation lasts 65-70 days and the altricial young are born in late August until early October. There are 1-5 pups in a litter (usually 2-3) and they stay in the family den until they are 2-3 weeks old. They can open their eyes after 1 month and start to regularly follow their parents out of the den. Young are weaned at the age of 3-4 months. At 9-10 months they can hunt independently and look just like their parents. Reproductive maturity is reached when they are 2 years old.
Habitat fragmentation and loss, as well as pollution, are the current major threats to the Giant otter, as the areas where they live are degraded and destroyed by logging, mining, and damming. This species was excessively hunted up until the late 1970s for its valuable fur. Illegal killing still occurs, often at the hands of fishermen, who see Giant otters as competition for fish. Some pups in the wild are taken for pets and usually die because of the inexperience of caretakers.
The IUCN Red List has no current estimate for the total Giant otter population. There are estimates for the populations of a few areas: 2,000-5,000 individuals in the Brazilian Pantanal; 180-400 individuals in Madre de Dios, southeastern Peru; 31 individuals in Cantao State Park, Brazil; 75 individuals in Amana, Brazil; at least 130 individuals in Balbina Lake, Brazil; 54 individuals in Araguaia, above Bananal Island; 32 individuals in Yasuni National Park, Ecuador; and at least 35 individuals in Rewa Head, Guyana. Estimates have been provided for the following countries: 60 animals in Bolivia in the northwest in the Madre de Dios-Beni sub-basin; 50 individuals in 118,031 km² of the Pantanal (Paraguay river sub-basin), and 600 animals in the 186,460 km² of the northeast (Itenez sub-basin), totaling an estimated 700 individuals; less than 250 animals in Ecuador; at least 200 animals in French Guiana; and 24-32 animals in Paraguay. Overall, currently, Giant otters are classified as Endangered (EN) and their numbers today are decreasing.