The life span of whales

The life span of whales is 50 to 100 years.

In the natural environment, the average life span is 50 to 100 years, and it can survive for decades. Whales were once regarded as ancient animals, and their life span was thought to be 500 ~ 1000 years. In fact, the average life span is only 30 years, and the longest life span is no more than 100 years.

The life span of beluga whales is generally 30 to 40 years, blue whales are at least 80 years, killer whales are generally 20 to 35 years, and baleen whales are generally 40 to 50 years. Although the whale is very big, it is completely active all day, and even sleeping is not still. In terms of body size ratio, its metabolic rate is particularly high compared with other large animals, so its life span is relatively short.

Cetacea (scientific name: Cetacea) is a traditional taxon under the phylum Mammalia, including about 90 existing naked-skinned fish aquatic mammals and their early extinct relatives. Whales? Or? Cetaceans are traditionally called whales (English: whales) and dolphins (English: dolphins). Most of them live in shallow water, and a few species live in fresh water.

The whale's body structure and living habits are obviously different from those of any mammal, so it has been listed as an order for a long time. Its ancestors and evolutionary history were once controversial, but with the continuous progress of related research, it has been completely confirmed that cetaceans evolved from terrestrial cloven-hoofed animals after entering the water 50 million years ago. DNA sequencing shows that cetaceans and hippos are sister groups, and their branches and ruminants are sister groups. In order to prevent cloven-hoofed animals from becoming a joint group (that is, lacking some evolutionary branches), whales are classified as cloven-hoofed animals in the current classification and downgraded to Cetacea.

Morphological characteristics:

Cetaceans are the most adapted to life in water among modern mammals. In the process of transition from terrestrial to aquatic, they evolved into fish-like shapes, and at the same time, their body hair also deteriorated (some whales still have a small amount of bristles in their noses and mouths, most species have faded during their growth, and a small number of species have remained for life). As whales finally become completely aquatic, sweat glands and sebaceous glands also deteriorated.

Seen from the side, the whale is round, slightly barrel-shaped and streamlined. Most kinds of cervical vertebrae are healed, and the head is directly connected with the body. It is impossible to twist the head without moving the body. The forelimbs are specialized into flippers with phalanges left inside. The hind limbs completely degenerated, leaving only 1 pair of small bone fragments. The rear part of the trunk is a tail handle, and the left and right ends of the tail end are opened to form a horizontal tail fin, which can swing up and down to push the body forward. Most cetaceans have dorsal fins, which are located behind or in the middle of their backs.

Small eyes, no transient membrane and lacrimal gland, poor vision. There are no auricles, only tiny ear holes, but they can hear well in water and air. The external nostril is located on the top of the head, commonly known as the spray hole. Breathe with the lungs, each 1 lobe. The stomach is divided into three chambers. All cetaceans except freshwater dolphins are rich in 1 layer of fat, which can keep warm, reduce the specific gravity of the body, increase buoyancy, and help to swim and breathe. The trachea and esophagus are completely separated, so you can't breathe through your mouth.

Baleen whales have no teeth in their mouths, and there are 150-400 strands of horny baleen whales on both sides of the maxilla. The color, quantity and shape of baleen vary from species to species, which is an important basis for classification; They use baleen whales to filter krill, small fish, cephalopods and shellfish in seawater, and the food is swallowed directly without chewing. The baleen whale is the largest animal in the world, and the female is bigger than the male.