Why dolphins are cast ashore

Why are dolphins being cast ashore?

Un gruppo di volontari socorre le balene spiaggiate a Golden Bay, Nuova Zelanda, 10 febbraio 2017
(REUTERS / Ross Wearing)

Well, just reported that in New Zealand, about 200 more black grind dolphins jumped to the land in the vicinity of Cape Fairwell in the north of the South Island. On all TV channels they show how volunteers try to save them, sprinkle them with water and wrap them in wet rags.

At the same time, about 400 days ago, about 400 grains were thrown out in the same area. As reported, most of them, up to 300 individuals, were already dead.

Such cases are not the first in history. Why it happens?

People found sea animals, which are not clear why they were thrown ashore, at least from the first century AD - ancient Roman and Greek documents testify to this. Today, marine biologists come to name the reasons for only half of such incidents, and these reasons are very different.

In 2002, 55 whales were released on the Cape Cod Bay coast. Thanks to the efforts of American rescuers, 46 animals were rescued. People poured water on the whales and covered them with wet towels, preventing them from overheating.When the tide began, the whales were dragged into the water. Alas, some of these marine animals have not waited for the tide.

In 2004, in the area of ​​the Canary archipelago, 15 whales were released on the shores of the two islands. Only three of them managed to be saved.

In June 2005, about 160 whales were released on the Australian coast. Rescuers with the help of volunteers did not let the five-meter “fish” die.

In October 2005, 70 whales died on the beaches of the island of Tasmania (Australia).

In March 2007, 12 whales were released on the shore of one of the Galapagos Islands. Despite the best efforts of rescuers, seven animals died.

In 2012, only on the Cape Cod Peninsula, 177 ordinary dolphins were stranded and 124 died, according to reports by the Associated Press. The report also mentioned that in total this number of dolphins exceeds the average of 37 animals, which was recorded in the previous 12 years.

More than 200 dead dolphins were thrown onto the beaches of Chiclayo, Peru. In this case, they found not only dead dolphins, but also dead fish - anchovies. Since this little fish is food for dolphins, they may be sick because of these fish, but the cause of death of animals remains a mystery.

Why it happens ?

Often it is a trauma or a disease.An animal injured by a predator may feel too weak to float, at some point it gives up and allows the waves to carry themselves to the shore. In our case, the head of the marine program of the World Wildlife Fund Konstantin Zgurovsky suggested that cetaceans could be stunned by seismic or underwater sound systems of warships. According to the expert, there are also speculations about the contamination of animals with worms or poisoning by pollutants, such as heavy metals, that enter the ocean.

Climatic cycles could change the direction of movement of fish and other living creatures that dolphins feed on. Dolphins, pursuing prey, could swim close to the shore and be thrown onto the land. This makes sense when you consider that sardines and other fishes were thrown ashore in Peru with dolphins.

Much more mysterious are the cases when a whole group of animals are thrown onto the shore. One explanation that scientists offer is that whales and dolphins that hunt and migrate in small herds are victims of their own social structure.If a leader or dominant animal is stranded due to illness or injury, then the rest of the group may follow. Whales always help their kinsmen out of their pack. If one of the whales wandered into shallow water by mistake, he immediately starts giving signals to his congeners, and they rush to the rescue. Alas, whales, instead of saving a comrade, they themselves fall into trouble.

Another version is that the herd swims too close to the shore and does not have time to return at low tide.

In some cases, the massive "suicides" of marine animals commit soon after the active use of nearby military sonars. In 2000, in the Bahamas, for example, 17 animals of four different species (beak cocks, toothed whales, dwarf whales and spotted dolphins) were found on the coast for 36 hours - on the day of application of the sonar in these places and the next day.

Studies that the National Oceanic and Atmospheric Administration conducted after this incident showed that the most likely cause was naval echolocation devices. Research data suggests that sonar had an impact on the physical condition and behavior of marine animals.

The whales are perfectly oriented in the ocean, so biologists say that they have a magnetic compass in their brain, so that these marine inhabitants can navigate in the Earth’s magnetic field. If a geomagnetic obstacle occurs in front of the whales, their internal compass fails and they begin to swim in the wrong way. It is known that the rescued whales are often again thrown ashore. Perhaps this is precisely due to the breakdown of the compass - the whales have returned to the water, but they cannot navigate.

There is a theory of noise. This theory is the most popular today. Scientists say whales and dolphins are being destroyed by the deafening hum of submarines. Losing their ears, the whales cease to orient themselves and are cast ashore. The study of the bodies of the thrown out animals gave grounds to assume that the cause of suicide is decompression sickness (decompression sickness). This discomfort occurs when there is a sharp decrease in external pressure. Caisson disease is called the disease of divers, pilots and workers who work in caissons (underwater working chambers).

The strong noise under the water scares the whales, and they begin to rise too quickly to the top - there is a sharp decrease in external pressure. This provokes the occurrence of a caisson disease in whales.Echo sounders, radar, sonars, rockets, submarines can frighten whales. This version is supported by the facts - there are several examples of the fact that the whale was released at the time of the military exercises using sonars.

It also happens that animals are thrown onto the beach intentionally - for hunting. Black killer whales, for example, often attack pinnipeds, such as seals or sea lions, in the surf zone or almost on the coast, where their victims change their way from swimming to walking and do it rather clumsily. While the animal is trying to get out of the water, the killer whale makes a dash and grabs the prey. After that, it remains either to wait for a suitable wave, or to try to return to the ocean, wriggling with the whole body.

Here is a video footage of one such hunt:

But 30 dolphins rushed to the shore:

Anyway, scientists have not yet come to a common opinion.

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  • Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

    Why dolphins are cast ashore

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