There are markers of Alzheimer's disease in the brains of three different species of dolphins.
Evidence of mass cetacean strandings exists but why dolphins and whales beach themselves in groups is a mystery.
Most mass strandings provide little to no clues, even though a direct link has been found between naval sonar and some beaked whales, and some individual animals washed up on shore have been clearly unwell.
There are at least five species of humans that we know of that are related to the toothed whales. Their ability to live past their reproductive years makes them vulnerable to late-onset diseases.
Alzheimer's is the most common cause of disability in old people. It looks like a similar problem may affect our water-dwelling mammals as well.
"Do only humans get dementia?" is a question that Frank Gunn-Moore has always wanted to answer.
The findings show that potential dementia associated pathology is not only seen in humans.
The brains of 22 stranded dolphins were examined to find markers for Alzheimer's disease. amyloid-beta plaques, which are thought to be a direct cause of the disease, are still present in elevated numbers in those who have it, and there are clusters of tau proteins with hyperphosphorylation.
The long-finned pilot whale and the white-beaked dolphin were found to have plaques of amyloid-beta. There were signs that these individuals were elderly, such as an increase in the ratio of white to grey matter in brain tissues.
The brains of dolphins and humans with Alzheimer's have the same locations of brain damage.
It was not possible for the researchers to confirm an Alzheimer's diagnosis because they couldn't test the animals' levels of cognitive impairment.
"We were fascinated to see brain changes in aged dolphins like those in human aging and Alzheimer's disease."
It's possible that dolphins help fellow dolphins who are struggling with their brain issues. The researchers note that there's a chance they'd survive for longer and allow further progression of the disease.
The'sick-leader' theory of dolphin strandings is supported by the study of G. melas.
According to Vacher and colleagues, the first symptoms of cognitive decline in humans are confusion of time and place.
If the leader of a Pod of G. melas suffers from a similar decline in cognitive function this could lead to a stranding.
Whether these pathological changes contribute to these animals stranding is an important question for future work.
The research was published in a journal.
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