Wet Beast Wednesday: giant otter
A while ago, I made a Wet Beast Wednesday post about the adorable and endangered sea otter. That was a few years ago by this point (you can tell by my inability to write useful descriptive text back then). It it time to discuss wet weasels again? You otter believe it!
(Image: a giant otter resting on a log just out of the water. It is a long, slender mammal that loos like a weasel. Its fur is motly black or dark drown, but with white on the chin and neck. The toes are webbed and the tail is long and flat. End ID)
The giant otter (Pteronura brasiliensis) is, as you might guess from the name, the largest of all the otters and the longest (but not heaviest) of the mustelids, the family that includes otters, weasels, and badgers. Males typically reach 1.5 to 1.7 meters (4.9 to 5.6 ft) while females reach 1 to 1.5 m (3.3 to 4.9 ft) long with a tail that can add an extra 70 cm (28 in) to that. They have slender, streamlined bodies with short but incredibly dense fur. The fur is so dense it prevents water from reaching the skin, therefore keeping the animal warm underwater and providing it with buoyancy. The toes are webbed and have large claws. The tail is muscular and paddle-shaped and provides propulsion when the otter swims. They have large eyes with excellent vision underwater. Vision, hearing, and smell appear to be their primary senses. In addition, they have long whiskers sensitive enough to detect changes in water pressure and movement, allowing them to detect fish and other animals from a distance.
(Image: a close up of a giant otter's head as it looks out of the water. It has large eyes ans small ears. The snout and eyebrows have prominent whiskers. End ID)
Giant river otters are found in the Amazon River system and the Pantanal wetlands. They are diurnal predators who hunt fish but will also target crustaceans, snakes, and young caimans and boa constrictors when food is scarce. As they hunt primarily using vision, giant otters prefer shallow, clear waters. When prey is spotted, they will engage in extensive chases when needed. This behavior has given them the local nickname "water wolves". Because of their preference for shallow, clear water, giant otters can be used as indicator species. Hunting can be done solo or in groups. Giant otters are considered apex predators, though their young are vulnerable to snakes, caiman, and other predators. They also compete for food with a variety of other species, including caiman and river dolphins. Giant otters have been found with scars left by piranha bites, indicating possible competition, though the scars could also be the result of the piranha defending themselves from the otters.
(Image: a giant otter eating a stripy fish. It is holding the fish in its paws and biting pieces off. End ID)
Unusually for otters, giant otters are highly social. They live in family units of usually 3 to 8 but sometimes up to 20 members. These groups are dominated by a breeding pair who are usually the parents of the other group members. The groups will engage in cooperative hunting and play behavior together and also work to build and maintain a territory. Giant otters will build dens in areas with gently sloping banks. these dens consist of burrows that are often long and extensive, with multiple openings, some of which are far from the water. They will also dig latrines to keep their feces far from where they live. These latrines serve as markers of territory, along with scent markings and vocalizations. Giant otters will also patrol their territory to keep watch for intruders. Territorial disputes are settled with threat displays first, but if neither side backs down, they will fight. Giant otters are the most vocal of any species, with 22 recorded different noises used for different purposes. In addition, each group will have their own idiosyncrasies in their vocalizations which are passed down to their offspring. Interestingly, while giant otters are territorial with each other, they do not seem to be as aggressive with the neotropical otter (Lontra longicaudis), whose range overlaps with theirs. This is possibly because neotropical otters have a very different lifestyle and therefore don't provide much competition. Giant otter groups also cooperate to drive off potential threats and have been known to scare off much larger predators like caiman and jaguars.
(Image: a family of giant otters taking a nap. There is one large otter with four draped on or near it. End ID)
Detail on giant otter reproductive behavior is scarce. They appear to be fertile year round, but most matings are times so that the female will give birth during the dry season. Males initiate mating and the gestation period is 65 to 70 days. Females will give birth to a litter of usually 2 but sometimes up to 5 pups that are raised within the den. The pups are born blind and require extensive parental care. Both parents and older siblings will help care for the pups. The eyes do not open until four weeks and the pups cannot walk until 5 weeks. They will emerge from the burrow ate between 12 and 14 weeks. At this point, the family will start teaching them to swim and hunt. The reason births are timed for the dry season is that shallower and more isolated waters are easier to learn to hunt in as the fish are more tightly concentrated and often sluggish. After learning to hunt, the pups will subsist on a mixture of milk and fish and they do not fully wean until around 9 months. Giant otters will typically stay with their parents until sexually mature at around 3 years. At this point, they will leave the group and seek out a mate. The longest documented lifespan of wild giant otters is 8 years, but they have been seen to live to 17 in captivity.
(Image: a giant otter parent escorting four pups on land. The pups are smaller version of the adult. End ID)
Giant otters are classified as endangered by the IUCN. They were hunted extensively for their fur, leading to a population collapse that nearly led to extinction. After local and international laws regulated and banned the sale of their furs, hunting stopped, but poaching remains a threat. Giant otters now occupy roughly 20% of their historic range, with the greatest population being located in the Guianas. Human activity also poses a threat through habitat loss. Deforestation destroys their habitat and has resulted in their local extinction in southern Brazil. Human activity is also believed to stress them out and can lead to parents neglecting their pups. While there is an ecotourism market for tourists to view giant otters in the wild, said tourism may be harming them due to the stress caused. Fishermen also tend to view the otters as pests and may kill or chase them away. The current giant otter population is estimated to be around 5000, but deforestation is estimated to drop that number by 50% by 2045. Conservation specialists believe that the otters need large protected areas with no human activity or else these moist mustelids will be in jeopardy.
(Image: a giant otter sticking its head out of the water with its mouth wide open, showing many sharp teeth. End ID)
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