Did sonar kill whales?

Sonar drives whales to certain death

Years ago, researchers had found gas bubbles in blood vessels and organs during the autopsy of washed up whales. In the worst case, the vesicles destroy tissue and cause bleeding and tissue tears. The scientists suspected that the vesicles form when the whales are startled and then emerge from the depths too quickly. 21 experts have now presented a study in the "Royal Society Journal", according to which, among other things, Cuvier's beaked whales die of decompression sickness.

"In the presence of the sonar, they are stressed and swim violently away from the sound source and change their diving pattern," says Yara Bernaldo de Quiros, lead author of the study. She conducts research at the Institute for Animal Health at the University of Las Palmas de Gran Canaria. "So the stress response overrides the diving response, which causes the animals to accumulate nitrogen," she added. "It's like an adrenaline shot."

Extended diving cycles

US researchers had already reported in 2017 in the journal Royal Society Open Science that the 16 Cuvier-beaked whales equipped with transmitters reacted violently to sonar noises during military exercises. In order to escape the noise of the sound waves, the whales stayed longer in the deep diving phase, an average of 90 minutes instead of 60 minutes.

Whales like this mighty sperm whale are actually perfect divers

The marine mammals are actually perfect divers who can use echolocation to detect prey or an enemy. During the diving phase, the heart rate slows down, the blood circulation decreases, and the oxygen remains in the blood.

Relationship between maneuvers and mass strandings

One type of sonar in particular throws these whales out of balance: the medium-frequency active sonar (MFAS) developed in the 1950s to detect submarines. It is used today in naval patrols and exercises, particularly by the United States and its NATO allies.

From around 1960 ships began to send underwater signals in a range of around 5 kilohertz (kHz). This was also when the mass stranding of beaked whales began, especially in the Mediterranean. Between 1960 and 2004, 121 of these so-called "atypical" mass strandings took place, of which at least 40 were closely related to the maneuvers in terms of time and location.

Acoustic nightmare: Especially military sonar signals during maneuvers are a massive hit on whales

In 2002, 14 whales stranded in just 36 hours during a NATO maneuver off the Canary Islands. Outwardly there was nothing to be seen. Your body weight was normal and you had no skin changes or infections. But her veins were full of nitrogen gas bubbles and bleeding had severely injured her brain. The autopsy revealed further damage to other organs, as well as the spinal cord and central nervous system.

Prohibition of maneuvers in whale regions demanded

Spain has banned such naval exercises off the Canary Islands since 2004. "Until then, the Canary Islands were a hotspot for this type of" atypical "stranding," said the scientist Bernaldo de Quiros. "Nothing has happened since the moratorium."

Rescue no longer possible: stranded sperm whale carcass on the North Sea coast

The authors of the new study called for similar bans to be extended to other regions where endangered whales congregate. The Cuvier's beaked whale grows up to seven meters tall and mainly eats octopus and fish from the deep sea. The whale is listed as "vulnerable" on the IUCN's Red List of Endangered Species and is believed to have a global population of 5,000 to 7,000 animals.

  • What happens to stranded whales?

    Joint effort

    In 2017, residents of Aceh, Indonesia, took care of ten sperm whales that were stranded in shallow water. Volunteers managed to pull six of the animals back out into the open sea, but four animals died. Nobody knows exactly why whales get stranded, but there are tons of theories ...

  • What happens to stranded whales?

    Follow the leader

    Some species of whale live in social groups that have a leader who is followed by the other animals. If the lead animal gets close to the shore and has problems there, it can send out a distress signal. The whales that follow him may try to help him and end up stranded themselves. Whales may also get stranded while hunting prey.

  • What happens to stranded whales?

    Man-made strandings

    Another theory as to why whales become stranded is that overfishing of the oceans forces marine mammals to seek food in unfamiliar and potentially shallow waters where they can no longer come out. There is also some evidence that ship sonar disturbs and confuses animals as they migrate.

  • What happens to stranded whales?

    Death in the deep

    When whales die in the depths of the ocean, their bodies sink to the bottom, where they are a source of food for a wide variety of other animals and organisms. But animals already near the coast could wash up on the beaches, like this whale that appeared in Rio de Janeiro. When that happens, the animals will rot on the beach. This phenomenon can create other problems.

  • What happens to stranded whales?

    An explosive reaction

    While it doesn't seem to put off those sun worshipers, the stench of a rotting whale carcass could ruin many people's vacation. And the smell isn't the only problem. When one of these giants of the ocean dies and begins to rot, gases form in its stomach that lie beneath a thick layer of whale blubber.

  • What happens to stranded whales?

    A sandy grave

    Disposing of a whale that has washed ashore can be a daunting task. Because they are a public health hazard, they cannot be left to rot on the beach. Some environmentalists say the best thing to do is to bury them on the beach yourself, as happened in the case of the four whales that died in Aceh.