The “scarred head” of the animal kingdom

Hedgehog
When you mention the animal that is covered with thorns, the first thing that everyone thinks of is the hedgehog. It is a well-known small animal with a body length of about 20 cm, which is common in many places in Eurasia and Africa.

The hedgehog has thick and hard spines, generally about 16 mm in length and mostly less than 1 mm in diameter. The spines of an adult hedgehog are more than 5,000. These spines are hair variations, in which the spines on the back are longer and thicker, and the head and the two ribs are relatively short and thin. The spines are hollow, and the shape is thick at both ends of the middle, and the tip is pointed like a awning, and the end of the skin is swollen. The spines are oily, the texture is hard and tough, and it is not easy to break.

There are two main types of thorns: one is white or khaki at the base, and the tip is gray; the other is white at the base and brown at the tip. The distribution of different color spines also constitutes a complex body color of the hedgehog, which becomes a protective color for camouflage.

The hedgehog also uses these behaviors to maximize the defensive functions of these spines. When it encounters a predator, it quickly wraps its head, tail and feet in the middle, and the whole body’s spines erect outwards together to form a densely pointed “meat ball”, which makes the predator unable to make a mouth. These erected spines are not uniform in direction, but are oriented in all directions, thus making their defense system more rigorous.

To complete this “skill” in an instant, the hedgehog must also rely on the highly coordinated and precise control of the subcutaneous complex muscle system, especially the vertical muscles that are uniquely connected to the spines. Adjacent hair follicles are usually connected by the same set of vertical hair muscles, so that the attachment position and traction direction of the vertical hair muscles and the enlarged hair roots are different. When the muscles contract, the several spines connected to them will be pulled in different directions. Thereby the spines are oriented in different directions.

In addition, the spines on the hedgehog can also act as a shock absorber, so that a “ball” that is curled up into a ball can jump unscathed from the steps of the stairs one level at a time. The flexible and elastic spine combined with the rich fat under the skin has a great cushioning effect on the body of the hedgehog, which prevents it from accidentally falling in the activities of foraging, courtship and mating.

The process of beggars courtship is both procrastinating and noisy, including dramatic performances. The male hedgehog needs to be circled around the female hedgehog for several hours, because the mating must wait for the female hedgehog to actively cooperate, otherwise it will not be possible, as long as the female hedgehog slightly exerts the spine, the male hedgehog will be unbearable. The newborn hedgehog pups have a smooth body and soft spines stick to the skin, but after 20 hours of birth, these soft thorns can stand up.

porcupine
The porcupine is also called the porcupine and the thorn pig. It is a thorny animal with the same name as the hedgehog. Porcupine spines mainly grow on the back, buttocks and tail. Although they are all made of body hair, they are spindle-shaped and hollow, but the porcupine’s thorn is different from the hedgehog in many respects.

The porcupine is larger in size, usually about 3 times that of the hedgehog. Its spines are thicker and longer, and the number is much larger than that of the hedgehog. An adult porcupine has more than 30,000 spines, and most of the spines are in a row of 3 to 5, which is born on the curved surface of the thick “meat scale”. Porcupine’s spines are longer and stiffer than hedgehogs, with longer spines up to about 200 mm and thickest parts up to 6 mm in diameter. In addition, the length, diameter and morphology of the porcupine spines vary greatly, even if the two adjacent spines are often in different shapes, which is also different from the hedgehog.

The biggest difference is the thorn on the tail. The dozens of spines at the end of the porcupine evolved into bristles, and the tops were swollen and shaped like a group of “small bells.” When walking, these “small bells” collided with each other, making a loud, crisp, squeaky, squeaky sound. It can be heard dozens of meters away. It seems that it is warning to the predators who lick it: Don’t come close to me, I am not irritating.

Usually, the spines on the porcupine are attached to the body surface, and when the enemy is attacked, the spine of the body is quickly erected, but it cannot collapse its body into a ball like a hedgehog, but backwards the body. The other side hits. This behavior shows that it is no longer satisfied with the simple passive defense like the hedgehog, but with the help of the physical spine.

Sometimes, it can also eject the spine of the back by the strength of the muscles one by one, just like the bow and arrow, but the power of these “arrows” is very small, there is no lethality, maybe just scare and scare The enemy only. However, because of the scallops on the spines, which help to make the spines slowly penetrate into the flesh, once the predator is stabbed into the flesh, it will be hurt, and if it is serious, it will be fatal. danger.

For the porcupine’s love life, avoiding being stabbed is of course the most noteworthy detail. At the time of mating, the female porcupine turns her back to the male porcupine and arches the tail to the top of its back, because there is no spine under the tail of the female porcupine, and the abdomen of the male porcupine has no spines. The porcupine’s pups are also better than the hedgehog, and they are born with a fully developed spine that can be used within 20 minutes of birth.

Acupuncture
Acupuncture is also a mammal that is a thorn, but it seems to be little known compared to hedgehogs and porcupines, because it is only distributed in Papua New Guinea and Australia, so it is also called Australian Acupuncture.

The shape of the acupuncture is roughly like a hedgehog, but the body shape is about twice that of the hedgehog. The back of the body is also covered with a long, short, hollow, hard spine formed by the hair, but with a cylindrical, hard, hairless scorpion at the front and curved downwards, with nostrils and mouths. The front end of the skull, the mouth is just a small hole, no teeth. These characteristics show that it is a very different animal from the hedgehog and the porcupine. In fact, they are far apart in kinship. Acupuncture is a close relative of the platypus. It is classified into the mammalian genus Aphididae in taxonomy. Its digestive tract, excretory tract and reproductive tract are open at the back of the body. Within the cloaca, it is thus the most primitive mammal.

Interestingly, the behavior of the acupuncture combines the characteristics of hedgehogs and porcupines. In the case of fright, it erects the spine and turns the body into a headless “bristle”, which is very similar to the hedgehog. Sometimes, it will also face the enemy, make the spine out of its body, and stab the invaders. After a while, the new part of the spine will grow, which is very similar to the porcupine.

Acupuncture does not seem to satisfy the above two tricks, but also strives to develop a unique defense skill. Because the front jaw of the needle is strong and strong, the tip of the toe has sharp claws, which is suitable for quick excavation into the ground. No matter how hard the soil on the ground is, it can be quickly digged and buried in the soil. Only the spine of the back is exposed, and the claws of the limbs and the spines on both sides of the body are nailed in the soil, and it is difficult for the external force to pull it out of the soil. In addition, it can hook the roots of the tree or fall into the cracks of the rock so that the predator can’t eat it.