narwhal: the unicorn's horn is actually its teeth

2020-01-06 | Animal Expo original |

Unicorns are animals in Western legends. They are said to resemble a horse and have a spiral horn on their heads. Although European unicorns have never seen a living unicorn in the Middle Ages, there are occasional values ​​in the market.The "unicorn horn" of Liancheng. Now we know that the prototype of a unicorn is the Indian big unicorn rhino, and the so-called unicorn horn is actually the fangs of a narwhal. Today we come to everyoneIntroduce "Marine Unicorn"-Narwhal.

narwhal

a close relative of the beluga

narwhal and beluga constitute the only two existing members of the narwhal family. The narwhal without horns and beluga look similar. They are medium-sized cetaceans with a body length of about 4Meters. They have no dorsal fins to suit swimming under the ice in the Arctic Ocean. Their kisses are extremely short, their foreheads are high, and there are melon-shaped fatty tissues inside. This is their echo-locating organ. Their cervical vertebrae are normally joined, andNot as fused as most cetaceans, so they all have necks, although short, which is different from other cetaceans.

? Comparison of narwhal body and human

The most significant difference between a narwhal and a beluga is its "horn", which is actually its tooth. This tooth is the left canine tooth of the narwhal, sticking out its lips and growing forward in a left spiral, for lifeThey are all growing, about 1.5-3.1 meters in length; the teeth are hollow and weigh about 10 kilograms. Except for this long tooth, the other narwhal's teeth have not been born in the alveolar, although it belongs to the suborder of tooth whale,But mouth full of teeth. Usually only male whale has tusks, 0.2% of male whale has two tusks, that is, the right canine tooth also grows; and 15% of female whale also has tusks.

Another difference is body color. As the name suggests, the white whale is white, and it is the only white whale. The narwhal has a white ventral surface and a mottled black pattern on the back on a white background.Whales are the darkest when they are born. The older they become, the whiter they become. Some older male whales are almost completely white, and it is difficult to distinguish them from beluga whales except for their long teeth.

ventral view and lateral view of narwhal

The narwhal family where narwhal and beluga are, together with the dolphin family and the rodent dolphin family, together constitute the dolphin superfamily of the subtooth whale suborder. Among them, the narwhal family and the rodent dolphin family are close relatives.The ancestors separated from the dolphin family 11 million years ago. Narwhal and beluga were originally living in tropical seas. They migrated to the Arctic in the evening Pleistocene ~ 3 million years ago as the marine food chain changed.I've settled here since then.

narwhal and beluga

Unicorn Horn

The tusks of the narwhal can be said to be a miracle of nature. People who have not seen the narwhal can hardly imagine that this is a real creature. Because of this, so many people in ancient Europe put this fang.Used as a unicorn's horn. Until recently, zoologists couldn't figure out what this long tooth was useful for. People have put forward many hypotheses. If anyone thinks that a unicorn digs a clam with long teeth to eat on the sea floor or pierce the iceLayer of breathing air. In fact, the narwhal's long teeth are relatively fragile and difficult to use as tools for digging or breaking ice.

narwhal

In 2014, a research team from Harvard University confirmed that the narwhal's long teeth are actually a sensory organ. The enamel layer of the long teeth is covered with pores, and there are thin tubes leading to the inside. There are many nerves in the pulp.The tip is connected to the brain, and is extremely sensitive to changes in seawater temperature, pressure, and salinity, which can help male whales find food, breathing holes, and female whale in estrus. Researchers have found that narwhal can taste the salinity of water with long teeth, whenWhen its long teeth are placed in water of different salinity, its heart rate will change significantly.

Because usually male whale has long teeth and female whale does not, people can easily think that long teeth are related to competition for sexual selection. Some people think that male whales use long teeth as a weapon to compete for their spouse, or to show off and display tools.To the ritual of male whale tusks. Now studies have confirmed that male whale tusks are actually exchanging physical and chemical information collected from the water with each other, which is a way of intra-species communication and has nothing to do with grabbing a wife.

"Tooth decay" of male whale

In 2017, WWF researchers discovered a new use of narwhal tusks. From the images taken by drones, narwhal can track cod with tusks when the cod is close to the teeth.When it is sharp, it knocks the cod quickly and forcefully, causing it to temporarily comatose, and then opens its mouth to swallow it.

The narwhal has a short kiss and no teeth. It can only wait for the fish to swim close to the mouth and suck it into the mouth. When it swims close to the school of fish, the fish is already stunned. Therefore, the narwhal runs away.Quietly approaching with long teeth and suddenly stun the fish before swallowing it is indeed a good way to catch fish.

narwhal

Residents of the Arctic

A narwhal is an inhabitant of the Arctic Ocean. Like the beluga whales, it is the most northerly whale. The narwhal has a migration habit. When it is cold, it swims northward, looking for the sea with many ice floes.In autumn and winter, it inhabits the offshore waters of Baffin Bay and Davis Strait. The open water here is very limited, and the area covered by floating ice is more than 95%. Under the floating ice, the number of benthic organisms, especially flounder, is particularly abundant.It is the narwhal's favorite prey.

distribution of narwhal

When the sea ice melts in the summer, the narwhal moves south to the ice-free sea area on the coast, where it spends two months. At this time, it focuses on cod, followed by flounder. The food is richer and easier to catch in autumn and winter.Contributes more to narwhal nutrition, and summer is a relatively food-starved period.

The narwhal can dive to a depth of more than 1500 meters, and the air is closed for more than 25 minutes. It is the sea animal with the strongest diving ability in the Arctic region. It dives more than 15 times a day to 800 meters or deeper, and the cumulative diving time is more than 3 hours.The narwhal feeds on benthic organisms and needs to breathe air. The strong diving ability solves this contradiction.

narwhal likes ice floes

Highly threatened by global warming

The biggest natural enemy of narwhal is killer whale. Scientists took a video in 2014. The killer whale group blocked the narwhal group in shallow waters for hunting, killing more than a dozen narwhal.How to escape to the deep sea and make use of its diving advantages to escape killer whale hunting. Sea ice can effectively suppress killer whale activity, so killer whales mainly harm narwhal in summer.

killer whale hunting narwhal

Once the narwhal arrives in the wintery land with many ice floes, the killer whale can hardly do anything about it. At this time, the polar bear becomes its number one natural enemy. The polar bear ambushes mainly around the breathing holes, attacking the narwhal that is exposed to the surface for ventilation.Polar bears are predominantly hunting juvenile whales, and adult narwhals are too big for it.

Polar bears have left the narwhal to have long teeth

Although the narwhal tooth was once valuable in the past, it has never been a major commercial whaling object, probably because it is distributed too far north. Now Westerners' understanding of the value of the narwhal tooth is gradually returning to rationality., Just as a collection of ordinary art, no longer give it special witchcraft or medicinal value. At present, the Inuit people kill some narwhal every year, the annual killing is about 1,000. According to expert evaluation, the global independentThere are about 170,000 horned whales, which are generally non-endangered species, and this kill is negligible.

The biggest threat to narwhal is climate warming. Climate warming has expanded the area of ​​ice-free sea surface, greatly increasing the chance of narwhal encountering natural enemies. As killer whales enter Hudson Bay, a large number ofNarwhal, especially juvenile whales, have been slaughtered. In recent years, the Inuit have also found it easier to encounter and catch narwhals than in previous years.

The tusks of narwhal have commercial value

As assessed by experts, narwhal is one of the most sensitive creatures to global warming and is more sensitive than polar bears. This is mainly due to the higher demand for habitats by narwhals. Polar bears are breathing and hunting on the ice.The narwhal not only has to breathe on the sea surface, but also eat flounder on the sea floor. The round-trip distance from the breathing hole to the foraging place must be controlled within 1450 meters. Therefore, the narwhal can only live in the Arctic Ocean.In offshore waters, the depth of the water is within a few hundred meters, and it is not suitable for it to survive in the ocean. Polar bears can live near the North Pole for a long time, and narwhals cannot.

Climate warming delays the freezing of the waters around the Arctic Ocean in autumn. In winter, the weather is much more variable than before. Sudden low temperatures and windless weather conditions can easily freeze the breathing holes, making the narwhal unable to change.The narwhal needs to have a breathing hole width of at least half a meter. If there is no suitable breathing hole, the narwhal will be forced to give up some high-quality foraging points that are too far away, which will inevitably lead to environmental capacity in the long run.decline.

narwhal emerges for ventilation

Some people are optimistic about this. These people think that since the narwhal was migrated from the tropical area in the Pliocene, there should be some flexibility in adapting to the environment. However, the premise is that the environment should not change too quickly and there must be enoughBuffer, but now human-induced climate warming is 50,000 times faster than nature! The Arctic Ocean is the last home of narwhal, and they have no way back. If this area becomes no longer suitable for unicornsWhales survive, then this magical "sea unicorn" will disappear forever, so it's time to take action to protect them!


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