Whales are marine mammals from the order cetaceans. Some of them are among the largest animals in the world. The forelimbs are fins, the hind ones are absent. A thick layer of fat protects the body from hypothermia. Like all mammals, whales breathe air with their lungs, are warm-blooded and feed their young with milk from their mammary glands. Their body length can be up to thirty-three meters, and their weight is from thirty to one hundred and fifty tons. The number of whales is decreasing every year.
The main reason for the sharp decline in the number of whales is believed to be human influence, which takes completely different forms. Of great concern to whales are construction and drilling operations, oil and gas production, increased traffic and noise. Potential danger for the population is injury and death of whales as a result of powerful hydrodynamic shocks during underwater blasting operations, as well as their entanglement in cables or ropes. All this is forcing whales to leave their traditional feeding areas. Oil and petroleum products are the most common pollutants that enter the aquatic environment during extraction and transportation. Since ancient times, humans have exterminated whales and considered them as a source of meat and fat. Changes in the number of whales are largely determined by the intensity of fishing. Very often, the death of whales is due to changes in ocean currents that bring colder water from Antarctica. Whales swim in shallow waters to keep warm and are easy prey for poachers. The decline in whale populations is not only a result of fishing, but also due to a decrease in the number of areas that are favorable for breeding. The main source of food for whales is plankton. It consists of tiny algae that are very rich in nutrients. Plankton reproduction is influenced by the state of the water. Its increasing pollution significantly reduces the amount of plankton. A variety of small fish, shrimp and crabs that make up the diet of whales are caught in large quantities by humans. Therefore, whales have less and less food for their share. Whales have enemies. The most dangerous marine predator is the killer whale. Accidental encounters of whales with swordfish are not desirable. Mammals have a significant number of external and internal parasites that cause various diseases.
