cetaceans "suicide" on the beach may be related to the brain disease of an elderly cetacean animal leader and the resulting orientation disorder.
Alzheimer's disease is associated with neurodegenerative processes in the brain. It usually occurs in older people. Abnormal accumulation of amyloid and tau proteins can damage nerve cells and the connections between them, leading to severe deterioration of cognitive function. A few years ago, biologists showed that the same process could happen in wild animals. Amyloid plaques and neurofibromas characteristic of Alzheimer's disease were subsequently found in the brains of dolphins, , which are found in wild animals in nature.
Since then, Frank Gunn-Moore and his colleagues at several universities in Scotland have continued to study the disease in dolphins. During this time, they collected and analyzed brain tissue samples from 22 dolphins, representing five different species of dolphins, that were found discarded off the coast of Scotland. The findings were published in the European Journal of Neuroscience.
The paper's authors say all the pathological hallmarks of Alzheimer's disease were found in four dolphins from three different species, including amyloid plaques, tau protein accumulation and glial proliferation, which is caused by the replacement of dead neurons by glial cells , which are normally supposed to support and "maintain them". All of this suggests that neurodegeneration and dementia may not be unique to humans, although strictly speaking, cognitive decline in these dolphins has not yet been proven.
Furthermore, this work is consistent with a relatively new hypothesis that cetaceans were thrown ashore. So far, the most popular explanation for this suicidal behavior remains ocean noise pollution from ships and sonar, which is confusing and often harms these animals' sensitive echolocation organs. However, a few years ago, another idea emerged, linking tossing to a "sick leader" that could lead an entire flock to dangerously shallow water due to disorientation.
At that time, the authors of the hypothesis studied the simultaneous mass discarding of seven sperm whales and suggested that this could be caused by a viral infection that affected the oldest members of the group. But new work by Ganmel and colleagues offers another explanation. Among these individuals, the person who usually leads their group may develop neurodegeneration in old age. It is because of this that they lose their sense of direction, leading to the death of the entire group.
