You might not say it, but there are thousands of dolphins swimming in the southern North Sea. This is one of the dolphin facts we are going to discuss. The bottlenose dolphin also used to be common, but nowadays you see the white-beaked dolphin more often. Every now and then, common dolphins or white-finned dolphins are spotted.
Even rarer are gray dolphins, striped dolphins, orcas and pilot whales. The beaked whales form a separate group, which also includes the butskhead. These are animals of the ocean, which occasionally end up in the North Sea.
You might also want to read about remora fish.
Dolphin facts: not seeing but hearing
Dolphin facts: Dolphins recognize each other because each animal has its own “whistle. They use it to call each other. To find food, dolphins use their ears instead of their eyes. From their heads, dolphins can emit high-pitched beeps that bounce off a fish, for example. The reflection is picked up in the dolphin’s lower jaw. This is called echolocation and with it a dolphin can determine how big the fish is, which way it is swimming and how fast the fish is swimming.
The dolphin can control the strength of the beep. Thus, in a noisy sea, dolphins must beep louder than in a quiet sea. Moreover, they can hear the echoes back worse. Dolphins and porpoises are therefore greatly affected by underwater sounds made by humans, such as from ship engines. Consider also that sound propagates much more strongly and farther under water than in air above water.
How do dolphins sleep and breathe?
Dolphins breathe through the blowhole on top of their head. They cannot breathe unconsciously, as humans do. They have to keep thinking about the next bite of air they need to get to the surface. If they were to fall asleep like humans they would die. That’s why dolphins only sleep halfway. They can let one half of the brain sleep, while the other half takes over the important work of the sleeping half. In this way, the dolphin can still take a nap safely. When dolphins are injured, they are often helped by conspecifics. They hold the injured dolphin above the water.
Threats to dolphins
Between 1940 and 1965, many dolphins and porpoises disappeared from large parts of the North Sea. There were many toxins in the fish then. Because dolphins eat fish, they suffered greatly from these substances. In addition to pollution, dolphins suffer from underwater noise, shipping and construction work at sea. Finally, overfishing on the types of fish dolphins eat is a threat.
Protection of dolphins
In 1991, a number of countries signed the ASCOBANS agreement, which stands for “Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas. These countries commit to protecting the habitats of small cetaceans, improving research on distribution, reducing pollution and disseminating information. When porpoises and dolphins wash ashore, they are difficult to rescue. The SOS Dolphin Foundation helps whenever possible.