Teeth

The odontocetes includes monodontidae (belugas and narwhals), beaked whales, sperm whales, dolphins (including killer whales and pilot whales) and porpoises, for a total of about 75 species. Toothed whale species are much more numerous than baleen whale species.

The number of teeth of which varies from one species to another. Certain species of dolphins have over 160 teeth; in some species of beaked whales, however, the teeth of females will never develop to protrude out of the gums. The sperm whale is the largest of the toothed whales; it has between 30 and 60 teeth, which develop on the lower mandible only. Teeth do not seem to be essential however, as whales have already been found with missing or severely worn teeth, or with fractured jaws, but which were nevertheless able to feed. The largest whale tooth is found in the male narwhal: its long tusk is actually the upper left canine growing in a spiral, piercing the upper lip and reaching up to 2.7 metres long. This tooth is believed to be a secondary sexual characteristic or a sensory organ. It has been seen in a drone footage that narwhals also use the tooth to knock out cod fishes in the Arctic.

What are teeth made of?

As with other mammals, the teeth of whales are mostly dentin, also known as ivory, a 75% mineralized tissue that also contains collagen. In the dental root or roots, the dentin is covered with cement, which is similar to bone in terms of its composition. In the crown, the part of the tooth that protrudes from the gum, the dentin is covered with enamel, a 95% mineralized tissue.

The growth layers of dentin and cement can sometimes be used to determine the age of an individual, much in the same way as how growth rings of a tree are counted.

What is the purpose of teeth?

The answer might seem obvious: to eat! However, it is not so simple. Land mammals have several types of specialized teeth that allow them to capture prey or chew or tear their food. Additionally, their upper teeth fit nicely into those of the lower jaw, which facilitates chewing.

On the contrary, the teeth of an odontocete whale are very similar to each other and are not designed to fit together, features that say a lot about how they feed. Indeed, toothed whales catch their prey with their teeth and swallow them whole.

However, teeth do not seem to be essential, as whales have already been found with missing or severely worn teeth, or with fractured jaws, but which were nevertheless able to feed. Additionally, females do not always have teeth, especially in some species of beaked whales, but are still able to adequately feed.

In several species, the presence of (rake marks can be seen on the skin. Teeth might also be used for social or sexual activities.

Do whales have baby teeth?

Humans have two generations of teeth: deciduous teeth (from the Latin “to fall”) – also called “baby teeth” – and permanent teeth. Known as diphyodontia, this phenomenon is specific to mammals. However, odontocetes are an exception to the rule amongst mammals. They only have one set of teeth, which they keep for life.

Baleen

The mysticetes consists of four families : the rorquals, the gray whales, the right whales and the pygmy right whales.

What are baleen made of?

Baleen whales, which are amongst the largest animals on the planet, feed mainly on small organisms such as zooplankton (crustaceans such as krill and copepods) and small fish (capelin, herring, sand lances, etc.). These whales use their baleen like a sieve to filter out the water and retain their prey. Baleen consists of two hard plates sandwiching a series of very hard bristles. Baleen plates can be compared to two fingernails glued together with cat whiskers between the two. The baleen is arranged like vertical blinds across the upper jawbone. Depending on the species, baleen whales have between 150 and 400 baleen plates on each side of their mouth. Baleen, similar to human nails and hair, grows and wears continuously. On the baleen facing the inside of the mouth, the hard plates wear more quickly than the bristles, causing the latter to stick out from the “sandwich”. The bristles that stick out intertwine and form a filter through which water can easily flow, but which is efficient in retaining prey. Interestingly, whales of this group owe their scientific name to their baleen: Mysticeti translates as “moustached whale”!

There are several secrets in baleen plates. Their analysis allows researchers to discover a whale’s diet or to study variations in certain hormone levels.

Baleen measures one metre in adult blue whales, compared to 90 cm for fin and humpback whales, and 30 cm for minke whales. The bowhead whale holds the title for the longest baleen, at over 4 metres. Baleen is generally brown or black except in the minke whale, where it is cream-coloured.

Origin of baleen

The first whales had teeth, just like their terrestrial ancestors. Over time, some whales began feeding by suction, drawing in their prey with their tongue. The loss of teeth is believed to have given way to the appearance of baleen on the jaw, which allowed whales to filter their prey. To this day, tooth buds still appear at the embryonic stage of baleen whales, even though the latter never develop teeth. This is a vestige of their ancestor, which did have teeth.

Baleen babies?

At birth, whale calves have short baleen or no baleen at all, which facilitates nursing. The baleen develops slowly and begins to be functional at weaning, which is between 6 and 12 months depending on the species.

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