Which mammals can echo localize

Why do whales and dolphins strand?

Which whales and dolphins are stranded where?

The most common mass strandings are known from pilot and sperm whales, beaked whales and deep-sea dolphins. Baleen whales, which include all large whales with the exception of the sperm whale, very rarely get stranded.

If the mammals strand, they can dry out, overheat, suffocate or suffer serious internal injuries due to their enormous weight.

Individual strandings have already been observed in many places, most of the mass strandings were recorded in Western Australia, New Zealand (with up to 300 whales stranded annually), on the east coast of North America and Patagonia (Chile). Occasionally, however, there are also mass strandings in the North Sea.

On land, the mammals can dry out, suffocate or suffer internal injuries due to their enormous weight.

How do whales and dolphins orient themselves?

Similar to migratory birds, some whale species travel great distances every year. In winter, whales migrate south from the cold northern seas to warmer waters. And whales from the southern waters are drawn to the north. Months later, they start their journey home.

The smaller toothed whales like dolphins have powerful underwater sonar. They orientate themselves on their wanderings by emitting sound waves in the form of clicks. If these sound waves collide with an object, the reflected sound waves echo back to the ears, which in the case of whales are shielded from the skull in foam-filled chambers inside the body to enable spatial hearing. The faster the sound returns, the closer the prey, an obstacle, or the coast.

In the case of the large baleen whales, which have horn plates (whales) instead of teeth in their upper jaw and thus filter krill, animal plankton and small fish from the water, this underwater sonar is only very weakly developed.

Echolocation works very well in principle, but the sound reflection does not work reliably, especially in shallow or semicircular bays, sandy underwater embankments or mud banks. Because these coasts or obstacles do not echo back clearly from any direction. The warning system fails.

Even in the German Wadden Sea, whales like this not yet fully grown sperm whale are sometimes washed up

What influence does the earth's magnetic field have?

Whales like the pilot whale not only orient themselves through their underwater sonar, but - also like migratory birds - evidently also on the lines of the earth's magnetic field, because their migrations often run parallel to magnetic lines. The slight fluctuations in the earth's magnetic field should function like a kind of map.

Magnetite crystals were found in the skulls of the animals. The whales could be irritated by disturbances in the earth's magnetic field near the coast. Magnetic fields perpendicular to the mainland have also been linked to mass whale stranding in certain coastal regions.

There are also major changes in the earth's magnetic field every few years due to solar storms and sunspots due to particularly strong activities on the solar surface. It is precisely then that sperm whales, for example, get lost and strand in the North Sea, which also use geomagnetism as a natural navigation system.

Why do whales and dolphins strand?

The main cause of whale stranding is therefore considered to be the animals' navigation errors, but not all causes have been conclusively researched.

Another reason for mass strandings is certainly the social behavior of many whale species that are in groups, so-called whale schools, and are guided by a lead animal. A male sperm whale leads the way from the Arctic Ocean back to warmer waters. In the case of the killer whales, on the other hand, a mother or grandmother leads the group.

If the lead animal loses its orientation because it is confused or because, for example, parasites have attacked the lead animal's ear and it can no longer hear the echo of the clicks sent out, then the animals swimming along follow the lead animal in the wrong direction. If the leader is stuck in shallow water, the rest of the group stays with him, even if it means their undoing.

Sometimes this group membership goes so far, as observed with killer whales on the South African coast, that already rescued whales return to the beach after a mass stranding when another stranded whale calls for help.

In addition to navigation errors, the stranding can also have very natural reasons: sometimes, for example, smaller dolphins strand because they have fled from orcas and other predators in shallower waters or because they ventured too far into shallow areas while hunting schools of fish.

Occasionally, individual animals that have previously been injured by ship collisions, fishing nets or shark attacks, or that have been infected by infections or parasites, are washed ashore already dead.

Particularly high-performance military sonar devices have a massive impact on the orientation of marine mammals

Which human influences aggravate the situation?

In addition to natural factors, man-made underwater noise, for example from ships, ice breakers, oil rigs or military sonar devices, can have a massive impact on the orientation and communication of marine mammals. Disoriented, they flee from the strong sound waves. And since the density of water is much higher than that of air, sound travels around five times faster under water than in the air.

The strong military sonar deployments have particularly drastic effects. For example, beaked whales washed up dead on the coasts of Cyprus, the Canary Islands and the Bahamas following NATO maneuvers. The more than 200 decibels loud sonars had triggered the formation of gas bubbles in the blood vessels and organs of the marine mammals (as in the case of diving disease), which prevents the blood supply and leads to death.

Every helper is welcome - the mammals need to stay cool and moist

How can you help stranded whales and dolphins?

When a whale stranding is discovered, there is usually not much time left. Aid teams can only try to cool the stranded animals, to keep them moist and to bring the heavy animals back into the sea as quickly and gently as possible with combined forces.

In order to mobilize as many helpers as possible as quickly as possible, appropriate hotlines have been set up in some countries. For many exhausted animals, however, these immediate measures often come too late.

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    show teeth

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    Author: Sophia Wagner