Dolphins (scientific name: delphinidae) have the morphological traits typical of toothed cetaceans: spindle-shaped bodies; single crescent-shaped breathing holes; skull instills, maxilla extending backwards to overlap the frontal bone; asymmetry of the left side of the skull apical head; conical or nail-shaped teeth, etc. The most obvious variations are related to feeding organs such as the beak, upper and lower jaws, and teeth. The length and size of the beak, the number and size of the teeth, reflect the range of niches occupied by different species. For example, the total number of teeth has gone from only about 10 (Richter's dolphins) to a total of 250 (protosthetic dolphins). The shape is also largely variable. Only a few species, such as killer whales and pilot whales, are significant type II, while many more species may be slightly type II in body size, shape, color, and dorsal fin shape. Body size ranges from less than 1.5 meters (some species of the genus Dwarf Dolphin) to over 9 meters. Beak variation ranges from very long (Indian Ocean subspecies of the long-snouted true dolphin) to very short (white-beaked dolphin), and several genera (killer whales, pilot whales, killer whales, pseudo-killer whales, melon head whales) are completely beakless. Most species have a sickle-shaped dorsal fin, with a few being triangular (some subspecies of protosthes, male killer whales) or rounded (he dwarf dolphins). White dolphins (sousa spp.) form thickened ridges or humps at the base of their dorsal fins, and right-wing dolphins (lissodelphis spp.) have no dorsal fin at all. Body color variation varies from black and white to complex spots of black, white and gray.
Due to the extremely wide distribution and variety of dolphins, scientists have not been able to give exact data to count their existing numbers, but they cannot be blindly optimistic.
As early as 2008, the International Union for Conservation of Nature surveyed that about a quarter of the existing cetaceans and dolphins are threatened to survive to varying degrees, and even face extinction.
dolphin
Dolphins are large carnivores at the top of the food chain, and with the exception of the more ferocious sharks, marine life is largely no threat to them. It can be said that dolphins face such a survival dilemma, and the biggest driving force behind it is still humans.
The development of globalized fisheries has brought unprecedented fishing intensity and breadth, and it can be said that wherever there is fish, there will be more and more modern fishing tools and means. Despite the more environmentally friendly fishing techniques, traditional means are still everywhere, bringing disaster to dolphins around the world. It is intended to fish, but the accidental fishing of dolphins still happens from time to time; when the net is exhausted, the big fish and the small fish are collected in the net, and the dolphins can only watch their food become human food.
Dolphin hunting in parts of East Asia (Japan), South Asia, Southeast Asia, Africa, and South America has remained unchanged for thousands of years. According to statistics, in the 90 days after the arrest, 53% of the dolphins are depressed and die; the natural life expectancy of dolphins is an average of 45 years, and half of the captured dolphins die within two years after being arrested, and their average living life is only 5 years; in the artificial environment, dolphins are very susceptible to pneumonia, enteritis and other diseases, and will not live for seven years because of chlorine poisoning and long-term depression.
Human beings do not hesitate to dump all kinds of domestic garbage, industrial wastewater, as well as various pesticide pollution and oil field waste into the ocean and rivers, which has made the originally clear ocean turbid, and large accidents such as oil spills have occurred from time to time, which has further deteriorated the marine environment. In densely populated waters along rivers and rivers, eutrophication and heavy metal pollution have threatened the living environment of aquatic organisms, and the proliferation of toxic seaweeds has also made the waters here dangerous. Even at the top of the food chain, dolphins are not immune, their reproductive and immune systems are severely damaged, and their mortality rates are greatly increased. In 1987, hundreds of dolphins on the coast of New Jersey in the United States died of immune system dysfunction caused by red tide, and their bodies were full of abscesses.
Hearing is the dolphin's most sensitive sense, and predation, wandering, and playing all rely on hearing. All kinds of underwater engineering equipment and large and small boats that come and go day and night not only disturb the life of dolphins, dolphins and boats "crash" from time to time, the "noise pollution" of these human activities also makes dolphins overwhelmed, physically and mentally damaged, out of control behavior, pressure multiplication, and abnormal living habits.
In many river basins, it has become common practice to build dams, build fishing grounds, build flood control projects, and extract water resources. Artificially changing the living environment of dolphins, building various projects, blocking activities such as dolphin migration. The white-tipped dolphin was once a national treasure of which we were proud, but the completion of the Three Gorges Dam has also more or less accelerated its quiet disappearance.
Global warming, climate change, rising sea level caused by precipitation, water temperature and salt and other ecological and environmental changes, especially some coastal water temperatures in just half a century rose by 3 to 4 degrees Celsius, the rapid change, so that dolphins are overwhelmed, confused.
It can be said that the number cannot be clearly counted, not because of the wide distribution and large number, but more because human technology and cognition are very limited. In just a few decades, the water paradise they once roamed happily has become embattled and precarious.
Since January 2019, 1,100 dolphin carcasses have been washed up on the Atlantic coast of France. The bodies of these dolphins are mutilated and their fins are severed, which is unbearable. The number in 2018 has increased compared to 2017, and even the highest in 40 years. 90% of dolphin deaths are caused by entanglement in industrial fishing nets, and the reason for the surge in deaths remains a mystery. [1]
1. More than 1,000 dolphin carcasses are found on the coast of France this year: the bodies are mutilated and unbearable [Cited on 2020-01-09]
This article was co-edited by headline wikipedia users Happy 1978, Niceeeeeday, and Qiu Transshipment 1.