Welcome to the I Can't Sleep podcast,
Where I help you drift off one fact at a time.
I'm your host,
Benjamin Boster,
And today's episode is about otters.
Otters are carnivorous mammals in the subfamily Lutrini.
The 14 extant otter species are all semi-aquatic,
Both freshwater and marine.
Latrinea is a branch of the Mustelidae family,
Which includes weasels,
Badgers,
Mink,
And wolverines,
Among other animals.
Otters are distinguished by their long,
Slim bodies,
Powerful webbed feet for swimming,
And their dense fur,
Which keeps them warm and buoyant in water.
They are playful animals engaging in activities like sliding into water on natural slides and playing with stones.
Otters exhibit a varied life cycle,
With a gestation period of about 60 to 86 days,
And offspring typically stay with their family for a year.
They can live up to 16 years,
With their diet mainly consisting of fish,
And sometimes frogs,
Birds,
Or shellfish,
Depending on the species.
There are 14 known species of otters,
Ranging in size and habitat preferences,
With some species adapted to cold waters,
Requiring a high metabolic rate for warmth.
Otters hold a place in various cultures,
Mythology,
And religion,
Symbolizing different attributes and stories,
From Norse mythology to Native American totems and Asian folklore,
Where they are sometimes believed to possess shape-shifting abilities.
The word otter derives from the Old English word otter.
This and cognate words in other Indo-European languages ultimately stem from the Proto-Indo-European word wudr,
Which also gave rise to the English word water.
The gestation period in otters is about 60 to 86 days.
The newborn pup is cared for by the female,
Male,
And older offspring.
Females reach sexual maturity at approximately 2 years of age,
And males at approximately 3 years.
The den is built under tree roots or a rocky cairn,
More common in Scotland.
It is lined with moss and grass.
After one month,
The pup can leave the den.
And after two months,
It can swim.
The pup lives with its family for approximately one year.
Otters live up to 16 years.
They are by nature playful and frolic in the water with their pups.
Its usual food is fish and further downriver eels,
But it may also assemble frogs and birds.
Otters have long,
Slim bodies and relatively short limbs.
Their most striking anatomical features are the powerful webbed feet used to swim,
And their seal-like abilities for holding breath underwater.
Most have sharp claws on their feet,
And all except the sea otter have long muscular tails.
The 13 species range in adult size from 0.
6 to 1.
8 meters in length and 1 to 45 kilograms in weight.
The Asian small-clawed otter is the smallest otter species,
And the giant otter and sea otter are the largest.
They have very soft insulated underfur,
Which is protected by an outer layer of long guard hairs.
This traps a layer of air which keeps him dry,
Warm,
And somewhat buoyant underwater.
Several otter species live in cold waters and have high metabolic rates to help keep them warm.
Eurasian otters must eat 15% of their body weight each day and sea otters 20-25% depending on the temperature.
In water as warm as 10 degrees Celsius,
An otter needs to catch 100 grams of fish per hour to survive.
Most species hunt for 3 to 5 hours each day,
And nursing mothers up to 8 hours each day.
For most otters,
Fish is the staple of their diet.
This is often supplemented by frogs,
Crayfish,
And crabs.
Some otters are experts at opening shellfish,
And others will feed on available small mammals or birds.
Prey dependence leaves otters very vulnerable to prey depletion.
Sea otters are hunters of clams,
Sea urchins,
And other shelled creatures.
They are notable for their ability to use stones to break open shellfish on their bellies.
This skill must be learned by the young.
Otters are active hunters,
Chasing prey in the water or searching the beds of rivers,
Lakes,
Or the seas.
Most species live beside water,
But river otters usually enter it only to hunt or travel,
Otherwise spending much of their time on land to prevent their fur becoming waterlogged.
Sea otters are considerably more aquatic and live in the ocean for most of their lives.
Otters are playful animals and appear to engage in various behaviors for sheer enjoyment,
Such as making water slides and sliding on them into the water.
They may also find and play with small stones.
In 1990,
An otter was observed belly sliding in Singapore,
Likely as a form of amusement.
Different species vary in their social structure,
Some being largely solitary while others live in groups.
In a few species,
These groups may be fairly large.
For many generations,
Fishermen in southern Bangladesh have bred smooth-coated otters and used them to chase fish into their nets.
Once a widespread practice,
Passed down from father to son throughout many communities in Asia,
This traditional use of domesticated wild animals is still in practice in the district of Narail,
Bangladesh.
Norse mythology tells of the dwarf Odr habitually taking the form of an otter.
The myth of Otter's Ransom is the starting point of the Volsunga saga.
In Irish mythology,
The character Leigh Ban was turned from a woman into a mermaid,
Half human and half salmon,
And given 300 years of life to roam the oceans.
Her lap dog assumed the form of an otter and shared her prolonged lifetime and her extensive wanderings.
In some Native American cultures,
Otters are considered totem animals.
In popular Korean mythology,
It is told that people who see an otter will attract rain clouds for the rest of their lives.
In the Buddhist Jakarta tales,
The otters and the wolf,
Two otters agreed to let a wolf settle their dispute in dividing their codfish,
But it was taken away by the cunning wolf.
In Japanese,
Otters are called kawauso.
In Japanese folklore,
They fool humans in the same way as foxes and donuki.
In the Noto region,
Ishikawa Prefecture,
There are stories where they shapeshift into beautiful women or children wearing checker pattern clothing.
If a human attempts to speak to one,
They will answer,
Uraya.
And then answer,
Araya.
If anybody asks them anything,
They say cryptic things like,
Kawaii.
The sea otter is a marine mammal native to the coasts of the northern and eastern North Pacific Ocean.
Adult sea otters typically weigh between 14 and 45 kilograms,
Making them the heaviest members of the weasel family,
But among the smallest marine mammals.
Unlike most marine mammals,
The sea otter's primary form of insulation is an exceptionally thick coat of fur,
The densest in the animal kingdom.
Although it can walk on land,
This sea otter is capable of living exclusively in the ocean.
The sea otter inhabits near shore environments where it dives to the sea floor to forage.
It preys mostly on marine invertebrates,
Such as sea urchins,
Various mollusks and crustaceans,
And some species of fish.
Its foraging and eating habits are noteworthy in several respects.
Its use of rocks to dislodge prey and to open shells makes it one of the few mammal species to use tools.
In most of its range,
It is a keystone species,
Controlling sea urchin populations which would otherwise inflict extensive damage to kelp forest ecosystems.
Its diet includes prey species that are also valued by humans as food,
Leading to conflicts between sea otters and fisheries.
The sea otter is the heaviest,
The giant otter is longer but significantly slimmer,
Member of the family Mustelidae,
A diverse group that includes the 14 otter species and terrestrial animals such as weasels,
Badgers,
And minks.
It is unique among the Mustelids in not making dens or burrows and in being able to live its entire life without leaving the water.
The only living member of the genus Enhydra,
The sea otter is so different from other mustelid species that as recently as 1982,
Some scientists believe it was more closely related to the earless seals.
Genetic analysis indicates the sea otter and its closest extant relatives,
Which include the African speckle-throated otter,
Eurasian otter,
African clawless otter,
And Asian small-clawed otter,
Shared an ancestor approximately 5 million years ago.
The sea otter is one of the smallest marine mammal species,
But it is the heaviest mustelid.
Male sea otters usually weigh 22 to 45 kilograms and are 1.
2 to 1.
5 meters in length.
Those specimens up to 54 kilograms have been recorded.
Females are smaller,
Weighing 14 to 33 kilograms and measuring 1 to 1.
4 meters in length.
The average weight for adult sea otters that are in more densely populated areas at 28.
3 kg in males and 21.
1 kg in females was considerably lighter than the average weight of otters in more sparse populations at 39.
3 kg in males and 25.
2 kg in females.
Presumably less populous otters are more able to monopolize food sources.
Unlike most other marine mammals,
The sea otter has no blubber and relies on its exceptionally thick fur to keep warm.
With up to 150,
000 strands of hair per square centimeter,
Its fur is the densest of any animal.
The fur consists of long waterproof guard hairs and short underfur.
The guard hairs keep the dense under fur layer dry.
There is an air compartment between the thick fur and the skin where air is trapped and heated by the body.
Cold water is kept completely away from the skin and heat loss is limited.
However,
A potential disadvantage of this form of insulation is compression of the air layer as the otter dives,
Thereby reducing the insulating quality of fur at depths when the animal forages.
The fur is thick year-round,
As it is shed and replaced gradually rather than in a distinct molting season.
As the ability of the guard hares to repel water depends on utmost cleanliness,
The sea otter has the ability to reach and groom fur on any part of its body,
Taking advantage of its loose skin and an unusually supple skeleton.
The coloration of the pellage is usually deep brown with silver-gray speckles.
But it can range from yellowish or grayish brown to almost black.
In adults,
The head,
Throat and chest are lighter in color than the rest of the body.
The sea otter displays numerous adaptations to its marine environment.
The nostrils and small ears can close.
The hind feet,
Which provide most of its propulsion in swimming,
Are long,
Broadly flattened,
And fully webbed.
The fifth digit on each hind foot is longest,
Facilitating swimming while on its back,
But making walking difficult.
The tail is fairly short,
Thick,
Slightly flattened,
And muscular.
The front paws are short with retractable claws,
With tough pads on the palms that enable gripping slippery prey.
The bones show osteosclerosis,
Increasing their density to reduce buoyancy.
The sea otter presents an insight into the evolutionary process of the mammalian invasion of the aquatic environment,
Which has occurred numerous times over the course of mammalian evolution.
Having only returned to the sea about 3 million years ago,
Sea otters represent a snapshot of the earliest point of the transition from fur to blubber.
In sea otters,
Fur is still advantageous,
Given their small nature and division of lifetime between the aquatic and terrestrial environments.
However,
As sea otters evolve and adapt to spending more and more of their lifetimes in the sea,
The convergent evolution of blubber suggests that the reliance on fur for insulation would be replaced by a dependency on blubber.
This is particularly true due to the diving nature of the sea otter.
As dives become lengthier and deeper,
The air layer's ability to retain heat or buoyancy decreases,
While blubber remains efficient at both of those functions.
Plubber can also additionally serve as an energy source for deep dives,
Which would most likely prove advantageous over fur in the evolutionary future of sea otters.
The sea otter propels itself underwater by moving the rear end of its body,
Including its tail and hind feet,
Up and down,
And is capable of speeds of up to 9 km per hour.
When underwater,
Its body is long and streamlined,
With the short forelimbs pressed closely against the chest.
When at the surface,
It usually floats on its back and moves by sculling its feet and tail from side to side.
At rest,
All four limbs can be folded under the torso to conserve heat,
Whereas on particularly hot days,
The hind feet may be held under water for cooling.
The sea otter's body is highly buoyant because of its large lung capacity,
About 2.
5 times greater than that of similar-sized land mammals,
And the air trapped in its fur.
The sea otter walks with a clumsy rolling gait on land and can run in a bounding motion.
Long,
Highly sensitive whiskers and front paws help the sea otter find prey by touch when waters are dark or murky.
Researchers have noted when they approach in plain view,
Sea otters react more rapidly when the wind is blowing towards the animals,
Indicating the sense of smell is more important than sight as a warning sense.
Other observations indicate the sea otter's sense of sight is useful above and below the water,
Although not as good as that of seals.
Its hearing is neither particularly acute nor poor.
An adult's 32 teeth,
Particularly the molars,
Are flattened and rounded for crushing rather than cutting food.
Seals and sea lions are the only carnivores with two pairs of lower incisor teeth,
Rather than three.
The adult dental formula is 3.
1.
3.
1 over 2.
1.
3.
2.
The teeth and bones are sometimes stained purple as a result of ingesting sea urchins.
The sea otter has a metabolic rate two or three times that of comparatively sized terrestrial mammals.
It must eat an estimated 25-38% of its own body weight in food each day.
To burn the calories necessary to counteract the loss of heat due to the cold water environment.
Its digestive efficiency is estimated at 80-85%,
And food is digested and passed in as little as 3 hours.
Most of its need for water is met through food,
Although in contrast to most other marine mammals,
It also drinks seawater.
Its relatively large kidneys enable it to derive fresh water from seawater and excrete concentrated urine.
The sea otter is diurnal.
It has a period of foraging and eating in the morning,
Starting about an hour before sunrise,
Then rests or sleeps in midday.
Foraging resumes for a few hours in the afternoon and subsides before sunset,
And a third foraging period may occur around midnight.
Females with pups appear to be more inclined to feed at night.
Observations of the amount of time a sea otter must spend each day foraging range from 24% to 60%,
Apparently depending on the availability of food in the area.
Sea otters spend much of their time grooming,
Which consists of cleaning the fur,
Untangling knots,
Removing loose fur,
Rubbing the fur to squeeze out water and introduce air,
And blowing air into the fur.
To casual observers,
It appears as if the animals are scratching,
But they are not known to have lice or other parasites in the fur.
When eating,
Sea otters roll in the water frequently,
Apparently to wash food scraps from their fur.
The sea otter hunts in short dives,
Often to the seafloor.
Although it can hold its breath for up to five minutes,
Its dives typically last about one minute,
And not more than four minutes.
It is the only marine animal capable of lifting and turning over rocks,
Which it often does with its front paws when searching for prey.
The sea otter may also pluck snails and other organisms from kelp and dig deep into underwater mud for clams.
It is the only marine mammal that catches fish with its forepaws rather than with its teeth.
Under each foreleg,
The sea otter has a loose pouch of skin that extends across the chest.
In this pouch,
The animal stores collected food to bring to the surface,
And sometimes a rock that is used to break open shellfish and clams.
At the surface,
The sea otter eats while floating on its back,
Using its fore paws to tear food apart and bring it to its mouth.
It can chew and swallow small mussels with their shells,
Whereas large mussel shells may be twisted apart.
It uses its lower incisor teeth to access the meat and shellfish.
Although each adult and independent juvenile forages alone,
Sea otters tend to rest together in single-sex groups called rafts.
A raft typically contains 10 to 100 animals,
With male rafts being larger than female ones.
The largest raft ever seen contained over 2,
000 otters.
To keep themselves from drifting out to sea when resting and eating,
Sea otters may wrap themselves in kelp.
The species exhibits a variety of vocal behaviors.
The cry of a pup is often compared to that of a gull.
Females coo when they are apparently content.
Males may grunt instead.
Sea otters in captivity have been observed forming sibling-like bonds with each other.
Two females at the Shedd Aquarium,
Kiana and Cayucos,
Maintained a big-sister-little-sister relationship,
With the younger Cayucos following around the older Kiana and mimicking her playful interactions with enrichment toys.
Formal assessment of social network formation and maintenance among sea otters has not been performed largely because researchers had simply assumed that rafts were composed of randomly assembled collections of individuals that aggregated after solitary foraging.
However,
According to UC Santa Cruz professor Tim Tinker,
Preliminary analysis of long-term spatial associations between tagged sea otters in Monterey Bay indicates that several distinct clusters occur within the large aggregations.
Some individuals also show consistent associations over many years.
As a result,
Formal network analysis for sea otters may reveal important information on the species and its social structures.
Sea otters have demonstrated the capacity for social learning,
With knowledge passed down both vertically from mom to pup,
And horizontally within groups.
Although whether or not they display a full-fledged culture remains unknown and under-researched.
Sea otters live in coastal waters 15 to 23 meters deep and usually stay within a kilometer of the shore.
They are found most often in areas with protection from the most severe ocean winds,
Such as rocky coastlines,
Thick kelp forests,
And barrier reefs.
Although they are most strongly associated with rocky substrates.
Sea otters can also live in areas where the seafloor consists primarily of mud,
Sand,
Or silt.
Their northern range is limited by ice,
As sea otters can survive amidst drift ice,
But not land-fast ice.
Individuals generally occupy a home range a few kilometers long and remain there year-round.
