The largest and one of the rarest of the otter species with a length,
including tail, of up to 6 feet and a weight of up to 70 pounds. Most
of the tail is noticeably flattened. Their dark chocolate/brown fur
is extremely dense and water repellent so that water doesn't
penetrate through to the skin. It seems shiny when wet. Throat
markings on giant otters are effectively unique which facilitates
identification of individuals. The body is long, supple and
streamlined with webbed feet. Its sleek shape, flattened tail and
webbed feet allow it to move quickly through water. At slow speeds,
all four webbed feet do the paddling, but at top speed, the tail does
all the pushing and the feet only steer. The otter's nostrils and
ears close to keep water out. Their eyes are located near the top of
the skull, allowing otters to see above the surface while swimming
nearly submerged. A fat layer under the skin and its dense, oily fur
protect the otter in extremely cold water. The sense of smell is also
acute, but the senses of sight and hearing are less well developed.
Like
its close relatives, the giant otter has many adaptations that make
it successful in its watery world. The facial whiskers are extremely
sensitive to touch, enabling the otter to locate food items in muddy
water. Fish and crabs are detected in the murky waters, and food is
captured by mouth. Small fish are eaten while swimming, but large
fish are carried to land for a more sumptuous dinner. Extra large
lungs, along with its ability to use more oxygen in each breath than
humans do, make it an excellent diver. The giant otter is the South
American cousin to the sea and river otters of North America, as well
as those of Europe and Africa. It can grow to nearly twice as large
as its American counterparts
Giant otters range throughout South America except for Argentina, Chile and Uruguay. Found in river systems with, preferably, slow-flowing water plus swamps and shallow creeks. Although found in nearly all of South America there is major concern for their protection. Being noisier than most otters and active during the day, not to mention possessing an insatiable curiosity, the giant otter is easily hunted. Today, giant otters are protected by law, but illegal hunting still takes its toll.
However, gold mining, logging and agriculture ultimately pose a greater threat. All result in water quality degradation and habitat disturbance--facts that adversely affect the giant otter. Rarely seen outside of South America, the Philadelphia Zoo is the only zoo in the United States now exhibiting this unique species. Giant otters once were found throughout the tropical rain forests of the Amazon, down to Brazil's Pantanal, the world's largest wetland. Today they are found only in the most remote waters in tropical South America. Giant otters live in lakes and slow-moving rivers in forested areas.
While the giant otter is a champion in the water, it is important that it spend time on land as well. There is the matter of grooming; its fur must be well maintained to keep it waterproof. Often, it must move long distances across land to find new waterways. Large rest spots along rivers or lakes are cleared of all vegetation by otters. From there, some dig dens consisting of short tunnels leading to a single chamber. These dens serve as a nesting chamber for otter cubs born during the dry season.
Like all otter species, giant otters live in interrelated family groups with pair bonding. A dominant bonded pair leads the group and all unite in defense. They communicate by vocalization and scent marking. Separate groups respect each other's territory. They live in extended families of perhaps ten otters. They hunt cooperatively and share babysitting duties. The groups respect territories and do not fight with each other. Each group's stable social structure is centered on the life-bonded dominant pair, which is the only pair that reproduces. The group raises one to four cubs annually.
In wild giant otters primarily eat fish and crabs. Adults will eat up to 10 pounds of fish each day. In the Philly zoo they are fed a completely fish diet of carp, bass, tilapia, catfish and/or trout plus vitamin supplements, especially B-1.
Gestation 65 to 70 days with a litter averaging 2 but varying from 1 to 5. Otters give birth ashore in underground dens. Mothers put youngsters into the water at 2 months where they learn to swim. Young stay with parents for 2 to 3 years. Otter litters are born after a two-month gestation.
Family groups (usually four to eight otters, but sometimes as many as 20), made up of an adult pair and the young of the past two years, actively advertise their territory by marking several sites along "their" stretch of the river or lake. Otters or people can easily identify these marked sites. Sites consist of large semi-circles of cleared land, which serves as a communal toilet. The strong odor can be detected by humans for weeks and may be downright unbearable within the first few days after otters move in. Scent marking prevents otters from invading each other's territory; so, fights rarely occur. During the wet season, the giant otter is less territorial and follows spawning fish into the flooded forest.
In wild giant otters live up to 12 years. In captivity they have attained ages of up to 21 years.
Hunting for their luxuriant fur, along with habitat loss, has reduced their numbers to an estimated 2,000 to 5,000.
Giant otters have no predators except humans, who once hunted them widely for their fur. Their fur is among the finest in the world; so dense that water never reaches their skin. Hunting otters was profitable and easy. A single giant otter pelt was worth more than a year's annual wage for a local resident. Otters are very inquisitive, and groups approaching canoes to get a better look were easy targets. The fur trade nearly eliminated them by 1970.
In 1973, giant otters were listed on Appendix I of CITES, which means all trade in their pelts was prohibited. Prohibiting trade in pelts eliminated the biggest threat to the otter's survival. But giant otters are still shot by settlers who do not know the law and fishers who regard them as competitors.
Currently, the biggest threat to giant otters is habitat loss from human settlement and pollution. Protecting otters requires protection of their prey, and the fish stocks of the South American wetlands are pressured by habitat destruction, over fishing, and pollution. Mining is one significant source of pollution. Gold miners use mercury to separate ore from mud, using 2 to 3 grams of mercury to extract 1 gram of gold. They heat the gold and mercury compound to burn off the mercury. The mercury is released into the air during burning and it falls on the land and is washed into the water system as rain. All fish-eating predators, including otters, crocodiles, and humans, are threatened by mercury poisoning.
Another threat comes from simple human activities such as the use of motorboats or motorized canoes. Otters are very sensitive to disturbance and will abandon their range with the advent of human settlement. Most human settlement in South America is concentrated along waterways, so otters have been seriously affected by human encroachment.
Increased tourism is another potential problem for otters. Tourism is both a blessing and a threat. It brings money and attention to help conservation of otters. At the same time, unwitting tourists in motor boats can come too close to denning otters. If tourists are not careful, the stress of people invading their range can cause mother otters to stop producing milk and the cubs can starve to death.
Trade in otter fur was prohibited under CITES in 1973. Conservationists believe this step had a tremendous effect on otter survival, and their numbers may be increasing.
The remaining remote and pristine rivers, lakes, and wetlands of South America house a large variety of threatened and endangered species. These include spotted cats, marsh deer, giant anteaters, and other rare creatures. The Nature Conservancy and Ecotropica have created one sanctuary for these animals. These groups acquired the 81,510-acre Duroche Ranch in 1995.