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 the narwhal.
The narwhal,
Monodon monoceros,
Is a species of toothed whale native to the Arctic.
It is the only member of the genus Monodon,
And one of two living representatives of the family Monodontidae.
The narwhal is a stocky cetacean with a relatively blunt snout,
A large melon,
And a shallow ridge in place of a dorsal fin.
Males of this species have a spiraled tusk that is 1.
5 to 3 meters long,
Which is a protruding left canine thought to function as a weapon,
A tool for feeding,
And attracting maids or sensing water salinity.
Specially adapted,
Slow-twitch muscles along with the jointed neck vertebrae and shallow dorsal ridge allow for easy movement through the Arctic environment,
Where the narwhal spends extended periods at great depths.
The narwhal's geographic range overlaps with that of the similarly billed and closely related beluga whale,
And the animals are known to interbreed.
Narwhals inhabit the Arctic waters of Canada,
Greenland,
And Russia.
Every year they migrate to ice-free summering grounds,
Usually in shallow waters,
And often return to the same sites in subsequent years.
Their diet mainly consists of polar and arctic cod,
Greenland halibut,
Cuttlefish,
Shrimp,
And armhook squid.
Diving to depths of up to 2,
370 meters,
The narwhal is among the deepest diving cetaceans.
The animals typically travel in groups of three to eight,
With aggregations of up to a thousand occurring in the summer months.
Narwhals mate among the offshore pack ice from March to May,
And the young are born between July and August of the following year.
When communicating amongst themselves,
Narwhals use a variety of clicks,
Whistles,
And knocks.
There are an estimated 170,
000 living narwhals,
And the species is listed as being of least concern by the International Union for Conservation of Nature.
The narwhal was scientifically described by Carl Linnaeus in his 1758 publication,
Sistema Naturi.
The word narwhal comes from the Old Norse,
Narval,
Meaning corpse whale,
Which possibly refers to the animal's grey,
Mottled skin,
And its habit of remaining motionless when at the water's surface,
A behavior known as logging,
That usually happens in the summer.
The scientific name monodon monoceros is derived from ancient Greek,
Meaning single tooth,
Single horn.
The narwhal is most closely related to the beluga whale.
Together,
These two species comprise the only extant members of the family Monodontidae.
Monodontidaes are distinguished by their pronounced melons,
Short snouts,
And the absence of a true dorsal fin.
Although the narwhal and beluga are classified as separate genera,
There is some evidence of interbreeding between the two.
Most prominent are the remains of a whale described by marine zoologists as unlike any known species,
Which were found in West Greenland around 1990.
It had features midway between a narwhal and a beluga,
Indicating that the remains belonged to a hybrid between the two species,
A narluga.
This was confirmed by a 2019 DNA analysis.
Whether the hybrid itself could breed remains unknown.
Results of a genetic study reveal that porpoises and monodontids are closely related,
Forming a separate clade,
Which diverged from other dolphins about 11 million years ago.
A 2018 molecular analysis of monodontid fossils indicates that they separated from porpoises around 10.
82 to 20.
12 million years ago,
And they are considered to be sister taxa.
A latter phylogenetic study conducted in 2020 suggested that the narwhals split from the beluga whale around 4.
98 million years ago,
Based on data from mitochondrial DNA.
The fossil species Cassadia thermophylla of early Pliocene,
Central Italy,
Was described as a possible narwhal ancestor when it was discovered in 2019.
Fossil evidence shows that prehistoric monodontids lived in tropical waters.
They may have migrated to arctic and subarctic waters in response to changes in the marine food chain.
The narwhal has a robust body with a short,
Blunt snout,
Small,
Up-curved flippers,
And convex and concave tail flukes.
Adults measure 3 to 5.
5 meters in length and weigh 800 to 1600 kilograms.
Male narwhals attain sexual maturity at 12 to 20 years of age,
Reaching a length of 3.
5 to 4 meters.
Females reach sexual maturity at a younger age,
Between 8 and 9 years old,
When they are about 3.
4 meters long.
On average,
Males are about 70 centimeters longer and more than 75% heavier than females.
The coloration of the narwhal consists of a mottled pattern with blackish-brown markings over a white background.
Unlike most whales,
The narwhal has a shallow dorsal ridge rather than a dorsal fin,
Possibly an evolutionary adaptation to make swimming under ice easier.
Or to facilitate rolling.
The neck vertebrae are also jointed,
Instead of being fused as in most whales,
Which allows for a greater range of neck flexibility.
These characteristics are shared by the beluga whale.
Furthermore,
Male and female narwhals have differently shaped tail flukes.
The former are bent inward,
While the latter are swept back on the front margins.
This is thought to be an adaptation for reducing drag caused by the tusk.
The skeletal muscles of narwhals are highly adapted for prolonged periods of deep-sea foraging.
During such activities,
Oxygen is reserved in the muscles,
Which are typically slow-twitch,
Enabling greater endurance and maneuverability.
Narwhals also have a comparatively high amount of myoglobin in their blood,
Which helps to facilitate deeper dives.
It has a dense layer of blubber,
Around 50-100 mm thick.
This fat accounts for a third of the body mass and helps insulate from cold ocean temperatures.
The most conspicuous trait of male narwhals is a long,
Spiraled tusk,
Which is a canine tooth that projects from the left side of the upper jaw.
Both sexes have a pair of tusks embedded in the upper jaw,
Which in males erupts from the lip somewhere between two and three years of age.
The tusk grows throughout the animal's life,
Reaching lengths of 1.
5-3 m.
It is hollow and weighs up to 7.
45 kg.
Some males may grow two tusks,
Occurring when the right canine also protrudes through the lip.
Females rarely grow tusks.
When they do,
The tusks are typically smaller than those of males,
With less noticeable spirals.
Current scientific consensus indicates that narwhal tusks are secondary sexual characteristics,
Which indicate social status.
Further functions of the narwhal tusk are debated.
While some biologists suggest that narwhals use their tusks in fights,
Others argue that they may be of use in feeding.
The tusk is also a highly innervated sensory organ with millions of nerve endings,
Allowing the narwhal to sense temperature variability in its surroundings.
These nerves may also be able to detect changes in particle concentration and water pressure.
According to Martin Weijia,
Male narwhals may rid themselves of encrustations on their tusks by rubbing them together,
As opposed to posturing displays of aggressive male-to-male rivalry.
Drone footage from August 2016 in Tremblay Sound,
Nunavut,
Revealed that narwhals use their tusks to tap and stun small arctic cod,
Making them easier to catch for feeding.
Females,
Who usually do not have tusks,
Live longer than males,
Hence the tusk cannot be essential to the animal's survival.
Alongside its tusk,
The narwhal has a single pair of small vestigial teeth that reside in open tooth sockets in the upper jaw.
These teeth,
Which differ in form and composition,
Encircle the exposed tooth sockets laterally,
Posteriorly,
And ventrally.
Vestigial teeth in male narwhals are commonly shed in the palate.
The varied morphology and anatomy of small teeth indicate a path of evolutionary obsolescence.
The narwhal is found in the Atlantic and Russian areas of the Arctic Ocean.
Individuals are commonly recorded in the Canadian Arctic Archipelago,
Such as in the northern part of Hudson Bay,
In Hudson Strait,
In Baffin Bay,
Off the east coast of Greenland,
And in a strip running east from the northern end of Greenland to eastern Russia,
170 degrees east.
Land in this strip includes Svalbard,
Franz Josef Land,
And Sivernaya Zemlya.
The northernmost sightings of narwhals occurred north of Franz Josef Island,
At about 85 degrees north.
There are an estimated 12,
500 narwhals in the northern Hudson Bay,
Whereas around 140,
000 reside in Baffin Bay.
Narwhals exhibit seasonal migration,
With a high fidelity of return to preferred ice-free simmering grounds,
Usually in shallow waters.
In summer months,
They move closer to the coast,
Often in pods of 10 to 100 individuals.
In the winter,
They move to deeper waters offshore,
Under thick pack ice,
Surfacing in narrow fissures,
Or in wider fractures known as leads.
As spring comes,
These leads open up into channels,
And the narwhals return to the coastal bays.
Narwhals in Baffin Bay typically travel to northern Canada and Greenland,
Between June and September.
After this period,
They travel about 1,
700 kilometers south,
To the Davis Strait,
And stay there until April.
During winter,
Narwhals from Canada and West Greenland regularly visit the pack ice of the Davis Strait and Baffin Bay,
Along the continental slope,
Which contains less than 5% open water.
And hosts a high density of Greenland halibut.
Narwhals normally congregate in groups of 3 to 8 individuals.
Groups may be nurseries,
With only females and young,
Or can contain only juveniles,
Or adult males,
Bulls.
Mixed groups can occur at any time of year.
In the summer,
Several groups come together,
Forming larger aggregations,
Which can contain 500 to over 1,
000 individuals.
Male narwhals have been observed rubbing each other's tusks,
A behavior known as tusking.
When in their wintering waters,
Narwhals make some of the deepest dives recorded for cetaceans,
Diving to at least 800 meters over 15 times per day,
With many dives reaching 1,
500 meters.
The greatest dive depth recorded is 2,
370 meters.
Dives last up to 25 minutes,
And vary in depth depending on the season and local variation between environments.
For example,
In the Baffin Bay wintering grounds,
Narwhals tend to dive deep within the steep coasts,
Typically south of Baffin Bay.
This suggests differences in habitat structure,
Prey availability,
Or genetic adaptations between subpopulations.
In the northern wintering grounds,
Narwhals do not dive as deep as the southern population,
In spite of greater water depths in these areas.
This is mainly attributed to prey being concentrated nearer to the surface,
Which causes narwhals to alter their foraging strategies.
Narwhals have a restricted and specialized diet.
Due to the lack of well-developed dentition,
Narwhals are believed to feed by swimming close to prey and sucking them into the mouth.
A study of the stomach contents of 73 narwhals found Arctic cod to be the most commonly consumed prey,
Followed by Greenland halibut.
Large quantities of Boreal Atlantic armhook squid were also discovered.
Male specimens had a higher likelihood of showing two additional prey species within their stomach contents,
Polar cod and redfish,
Both of which are found at depths of more than 500 meters.
The study also concluded that the size of prey did not differ between genders or age groups.
Other items found within narwhals' stomach contents include wolffish,
Kaplan,
Skate eggs,
And sometimes rocks.
Narwhal diet varies between seasons.
In winter,
Narwhals feed on demersal prey,
Mostly flatfish,
Under dense pack ice.
During the summer,
They eat mostly Arctic cod and Greenland halibut,
With other fish,
Such as polar cod,
Making up the remainder of their diet.
Narwhals consume more food in the winter months than they do in the summer.
Like most toothed whales,
Narwhals use sound to navigate and hunt for food.
They primarily vocalize through clicks,
Whistles,
And knocks,
Created by air movement between chambers near the blowhole.
The frequency of these sounds ranges from 0.
3 to 125 Hz,
While those used for echolocation typically fall between 19 and 48 Hz.
Sounds are reflected off the sloping front of the skull and focused by the animal's melon,
A mass of fat which can be controlled through surrounding musculature.
Echolocation clicks are used for detecting prey and locating barriers at short distances.
Whistles and throbs are most commonly used to communicate with other pod members.
Calls recorded from the same pod are more similar than calls from different pods,
Suggesting the possibility of group or individual specific calls.
Narwhals sometimes adjust the duration and pitch of their pulse calls to maximize sound propagation in varying acoustic environments.
Other sounds produced by narwhals include trumpeting and squeaking door sounds.
The narwhal vocal repertoire is similar to that of the beluga whale.
However,
The frequency ranges,
Durations,
And repetition rates of narwhal clicks differ from those of belugas.
Age determination techniques using the number of periosteum layers in the lower jaw reveal that narwhals live an average of 50 years.
Though,
Techniques using amino acid dating from the lens of the eyes suggest that female narwhals can reach 115 ± 10 years and male narwhals can live to 84 ± 9 years.
Narwhals have coexisted alongside circumpolar peoples for millennia.
Their long,
Distinctive tusks were often held with fascination throughout human history.
These tusks were prized for their supposed healing powers and were worn on staffs and thrones.
Depictions of narwhal tusks in works of art,
Such as The Lady and the Unicorn,
Have found a prevalent place in human arts.
In Europe,
Narwhal tusks were highly sought after for centuries.
This stems from a medieval belief that narwhal tusks were the horns of the legendary unicorn.
Considered to have magical properties,
Narwhal tusks were used to counter poisoning and all sorts of diseases,
Such as measles and rubella.
The rise of modern science towards the end of the 17th century led to a decreased belief in magic and alchemy.
After the unicorn notion was scientifically refuted,
Narwhal tusks were rarely employed for magical purposes.
Vikings and Greenland Norse likely began the trade of narwhal tusks,
Which via European channels would later reach markets in the Middle East and East Asia.
It is unclear if they hunted the narwhals themselves or mainly recovered the tusks from the corpses of animals killed by orcas.
Narwhal tusks were given as state gifts to kings and queens throughout medieval Europe,
With the price of narwhal tusks said to have been a couple of hundred times greater than their weight in gold during the 18th and 19th centuries.
Ivan the Terrible had a jewelry-covered narwhal tusk on his deathbed,
While Elizabeth I received a narwhal tusk allegedly valued at 10,
000 pounds sterling from the privateer Martin Frobisher.
Both items were staples in cabinets of curiosities.
The toothed whales are a parvidor of cetaceans that includes dolphins,
Porpoises,
And all other whales with teeth,
Such as beaked whales and the sperm whales.
Seventy-three species of toothed whales are described.
They are one of two living groups of cetaceans.
The other being the baleen whales,
Which have baleen instead of teeth.
The two groups are thought to have diverged around 34 million years ago.
Toothed whales range in size from the 1.
4-meter and 54-kilogram vaquita to the 20-meter and 100-ton sperm whale.
Several species of odontocetes exhibit sexual dimorphism in that there are size or other morphological differences between females and males.
They have streamlined bodies and two limbs that are modified into flippers.
Some can travel at up to 30 knots.
Odontocetes have conical teeth designed for catching fish or squid.
They have well-developed hearing that is adapted for both air and water,
So much so that some can survive even if they are blind.
Some species are well adapted for diving to great depths.
Almost all have a layer of fat or blubber under the skin to keep warm in the cold water,
With the exception of river dolphins.
Toothed whales consist of some of the most widespread mammals,
But some,
As with the vaquita,
Are restricted to certain areas.
Odontocetes feed largely on fish and squid,
But a few,
Like the orca,
Feed on mammals,
Such as pinnipeds.
Males typically mate with multiple females every year,
Making them polygynous.
Females mate every two to three years.
Calves are typically born in the spring and summer,
And females bear the responsibility for raising them,
But more sociable species rely on the family group to care for calves.
Many species,
Mainly dolphins,
Are highly sociable,
With some pods reaching over a thousand individuals.
In Aristotle's time,
The 4th century BC,
Whales were regarded as fish due to their superficial similarity.
Aristotle,
However,
Could already see many physiological and anatomical similarities with the terrestrial vertebrates,
Such as blood circulation,
Lungs,
Uterus,
And fin anatomy.
His detailed descriptions were assimilated by the Romans,
But mixed with a more accurate knowledge of the dolphins,
As mentioned by Pliny the Elder in his Natural History.
In the art of this and subsequent periods,
Dolphins are portrayed with a high arched head,
Typical of porpoises,
And a long snout.
The harbour porpoise is one of the most accessible species for early cetologists,
Because it could be seen very close to land,
Inhabiting shallow coastal areas of Europe.
Many of the findings that apply to all cetaceans were therefore first discovered in the porpoises.
One of the first anatomical descriptions of the airways of the whales on the basis of a harbour porpoise dates from 1671 by John Ray.
It nevertheless referred to the porpoise as a fish.
Toost whales,
Along with baleen whales,
Are descendants of land-dwelling mammals of the artiodactyl order,
Even toad ungulates.
They are closely related to the hippopotamus,
Sharing a common ancestor that lived around 54 million years ago.
The primitive cetaceans,
Or archaeocetes,
First took to the sea approximately 49 million years ago,
And became fully aquatic within 5 to 10 million years.
The ancestors of toost whales and baleen whales diverged in the early Oligocene.
This was due to a change in the climate of the southern oceans that affected the environment of the plankton that these whales ate.
The adaptation of echolocation and enhanced fat synthesis and blubber occurred when toost whales split from baleen whales,
And distinguishes modern toost whales from fully aquatic archaeocetes.
This happened around 34 million years ago.
Unlike toost whales,
Baleen whales do not have wax ester deposits,
Nor branched fatty chain acids in their blubber.
Thus,
More recent evolution of these complex blubber trades occurred after baleen whales and toost whales split,
And only in the toost whale lineage.
Modern toost whales do not rely on their sense of sight,
But on their sonar to hunt prey.
Echolocation also allowed toost whales to dive deeper in search of food,
With light no longer necessary for navigation,
Which opened up new food sources.
