In 2012 around 800 dolphins were reported dead at the coastline in nothern Peru. It now seems as though the same thing is happening all over again, and all over the world there is news about the mystical mass stranding of dolphins.
In March 2012 ORCA went up north to look for dead dolphins after a call from a fisherman. At the first day of their expedtion they found over 600 stranded long-beaked common dolphins and around 20 Burmesiter Porpoise. The animals were from all different age spans. ORCA collected samples from fresh dolphins and found that all individuals had cracked ear bones and air bubbles in the organs. ORCA in company with local ecological police were the only ones present in the area and in total they reported in total 774 dead dolphins and 62 porpoises.
At the same time that the dolphins were found stranded, oil companies were looking for oil in the same area. To find oil the companies use ultrasound and send out pulses every five to ten seconds. With help of this it’s possible to create an acoustical image that helps to find the oil that is hidden beneath the rocks of the bottom of the sea. In the water the pulses that are sent out sound like explosions and can get as loud as 280-320 decibels. Compared to sound in the air the sound underwater travels five to ten times faster.
The dolphins and the porpoises have their breeding period during summer time, January to March, and therefore they were present in the same area in the ocean as the oil companies. Dolphins use echolocation to navigate, communicate and to catch prey, therefore they have a really sensitive and developed system for hearing under water. When underwater sounds become too loud and the vibrations too strong, this cause damage to the dolphins hearing system. Extremely loud sound leads to cracking of the ear bone and release of oxygen in the cirulatory system and other organs, eventually this lead to the death of the animal.
One theory that is suggested is that a toxic algae kills all the dolphins. Dolphins are not herbivores and if it were toxic algaes in the ocean other wildlife and even humans would also be effected. Another theory talks about a virus that may have caused the mass strandings of dolphins. If this was the case the dolphins would have shown clincial signs. They would be found in different states of the sickness, not all of them would have been found dead and the rate of death would be different in different age spans.
The current stranding of dolphins seems to be similair to the one in 2012 and even this time ORCA is working to help the dolphins.