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Adult Asian Small-clawed otters (Aonyx cinerea)

Otters (subfamily Lutrinae) are the aquatic branch of the splendid Mustelidae family which includes all sorts of highly successful predators like weasels, ferrets, polecats, otters, fishers, and wolverines.  We have already described the giant river otter of the Amazon, a magnificent apex predator which lives on anacondas and piranhas but there are also 12 other species of otters living throughout the Americas, Eurasia, and North Africa (and in the ocean).

European Otter (Lutra lutra)

All of the otters partake of the tremendous strength (and weakness) of the Mustelidae family.  They are ridiculously fast, powerful, and agile, but in order to keep up their swift lifestyles they have huge metabolic intake.  This means they must eat all of the time, and as predators their life is one endless hectic hunt.  Northern otters are at a particular disadvantage since they live in freezing rivers, lakes, and oceans.  In cold weather, European river otters have to eat 15% of their weight every day, while Sea otters must daily down an incredible 25% of their mass.  Fortunately a fast metabolism brings its own incredible reward: otters (like weasels and ferrets) seem to be effortlessly moving while everything else is standing still.

A group of sea otters (Enhydra lutris)

Otters eat a startling variety of prey.  Although fish is the staple of their diet they also opportunistically eat snakes, frogs, lizards, birds, eggs, small mammals, mollusks, crustaceans, and sundry other invertebrates.  Their need for calories keeps them from being too picky.  Despite their speedy metabolisms, otters live as long as dogs (and can survive even longer in captivity).  Different otters have different levels of sociability—the Oriental small clawed otters and the river otters are quite clannish and live in big playful groups.

Baby Asian Small-clawed otters (Aonyx cinerea)

In addition to being great hunters (and eaters) otters are famous for playing.  Their frolicksome antics are a joy to behold, so I found some video on Youtube, but be warned: the sound on my computer is broken so I have no idea what the narrator/soundtrack/music is like.  It might be slidewhistles or it might be 2 minutes and 56 second of the foulest curse words.  Maybe you should watch it on mute.



Perhaps because otters seem to appreciate life, people have a reverence for them (not that reverence stopped furriers from nearly driving several species extinct during the course of the past three centuries).  In the  the shapeshifting dwarf Otr prefers to spend his time as an otter until he is killed by the malicious trickster god Loki.  Loki is forced to cover the otter skin with treasure, but one whisker remains uncovered and so Loki was forced to part with his magic ring of power (which went on to wreak havoc, as magic ring inevitably do).  To Zoroastrians, the otter was reckoned to be truly pure–and thus sacred to Ahura Mazda, the uncreated god who represents the apogee of wisdom, light, and goodness in their pantheon.  So if, by bad luck, the evil dragon Ahriman happens to burn his way into this world and begins to destroy existence you might want to go be near some otters.  You know, even without the evil dragon, you should go spend time watching otters.  They’re just great animals.

The North American river otter (Lontra canadensis)

Since I have already written so many mammal posts I am creating a new blog category for mammals (I will leave out human concerns to concentrate on zoologic overviews of other species, but please remember that technically we too are mammals and all of the posts on this and every website could fall under this category).  To make way for the mammals I deleted the “celebrity” topic for good (I had hoped to make fun of our queasy fascination with lackwit celebrities–but other than an one sighting of the disquieting Richard Simmons, I had nothing). Begone vile celebrities! The age of the mammals has dawned.

The Giant Otter, Pteronura brasiliensis

I already have plenty of posts about goats, pigs, wombats, hyraxes, and bizarre intelligent monotremes with which to populate this category, but to kick the topic off properly I am writing today about the alpha-predator of the Amazon.  This mammal is the king of the Mustelidae (also known as the weasel family) and, if you have ever seen a lightning fast stoat hunting a rabbit, or smelled a skunk, or watched a badger drive off a bear, or witnessed a wolverine tear apart a moose, you will know that the weasel family is not joking around. [ed: what? When did you see any of this?] The largest mustelid is a particularly magnificent creature—the giant otter (Pteronura brasiliensis) which lives throughout the Amazon basin and Pantanal.  The giant otter is a long animal and males are up to six feet (2 meters in length) and weigh up to 100 pounds (45 kilograms).  Much longer males measuring nearly 8 feet in length were once reported but it is believed that extensive hunting may have eradicated all of the really giant giant otters.

An Immature Giant Otter held by Wildlife Conservation Worker Diane McTurk in Guyana

Giant otters are tremendously accomplished fishers living largely on cichlids, characins (such as piranha), and catfish, but, as an apex predator they are opportunists who supplement their diet with snakes, crabs, turtles, and caimans.  Although the otters are diurnal predators who hunt at daytime using their large acute eyes to find their prey, their hearing is also excellent and they possess extremely sensitive vibrissae (whiskers) to gauge the faintest water current.  Like other mustelids, giant otters have fast metabolisms and they eat about 10% of their body weight per day.  Their adaptations to aquatic life include webbed feet, ears and nostrils which clamp shut, powerful tails for swimming, and incredibly dense fur.  As with their cousins the sea otters, this valuable fur proved to be their undoing. During the nineteenth and early twentieth century they were hunted to the very threshold of extinction by furriers (and by fishermen who regard them as a clever nuisance). Their numbers still remain low today: only 2,000-5,000 giant otters are estimated to live in the wild.

Orphaned Giant Otter Cubs

Giant otters form family groups around a mated pair.  Older offspring from years past stay with this pair and help out rearing the young cubs before venturing off on their own. They travel widely through the inundated forest during flood seasons and spend the rest of the year based around a fishing camp which they build beside a lake or a choice stretch of river.  These camps consist of large multiple entrance home dens built under and around tree roots as well as several secondary locations (along with communal latrine areas).  The otters might also alter river beaches to be more to their liking by removing vegetation.  The fur of the giant otter is usually brown, red, or fawn and the otter’s bib is marked with cream and white stipples.  These are for identification purposes: otters “persiscope” up out of the water to get a better view of each other and to learn whom they are meeting.  Giant Otters are also famous for their complicated (and loud) vocalizations.

A Giant Otter "periscoping" (photo by Roberto Fabbri Wildlife)

Although the adult giant otter has no natural predators, young otters must look out for caimans, jaguars, and anacondas. Additionally the giant otters compete for prey with these creatures as well as with river dolphins, large predatory fish, and large turtles.  The otters are always on the lookout for dangerous stingrays and electric eels.  None of these natural threats, however, are particularly significant compared with the threat from habitat loss, logging, mining, and industrial pollution.

Some of the native humans indigenous to the great river basins believed the otters were river spirits who had, once taught valuable lessons to the first humans.  Other native peoples (particularly fishing people) held that the otters were worthless nuisances to be killed or run off whenever sighted.  Such sightings however grow increasingly rare as the giant otter, the longest mustelid, vanishes forever away from all but the wildest places in the rainforest.

A Wild Giant Otter Devouring an Armoured Catfish (photo by Roberto Fabbri Wildlife)

Ye Olde Ferrebeekeeper Archives

September 2020