Why Do Whales and Dolphins Beach Themselves, and Is Dementia to Blame?
Spend an afternoon walking along a seashore, and you could come across a distressing sight: a beached dolphin or whale, stranded in the sand. If you discover an animal when it’s alive, there’s still a chance to save it — that is, if you call the appropriate authorities in time. But if you spot a marine mammal that’s already dead, then there’s nothing to be done, the animal having died at sea or along the shore, abandoned by the waves.
The scene is a sad one, whatever the circumstances, but why do these strandings occur in the first place?
A team of biologists set out to answer that question in a study in Communications Biology. Turning to the brains of stranded dolphins, the team discovered that the animals showed disease signatures that were similar to those that are seen in people with dementia, suggesting that Alzheimer’s-like brain deterioration could be contributing to the dolphins’ time in the sand. Potentially intensified by toxic cyanobacteria, the team notes that this brain damage could increase as algal blooms do, also thanks to climate change.
Read More: The Unique Relationship Between Whales and Dolphins
Are Marine Mammals Beaching Themselves?
Thousands of stranded marine animals are reported to the authorities annually, according to the National Oceanic and Atmospheric Administration (NOAA). Although some strandings result in rescues, in which professional responders (such as NOAA’s stranding partners) assess and stabilize an animal before releasing it or bringing it back to a rehabilitation center, many result in death, when the stranded animal becomes dehydrated or — in the case of dolphins or whales — drowns.
But despite the prevalence of strandings among dolphins and whales, scientists still aren’t sure why these marine mammals beach themselves. So, to address this, the biologists behind the study analyzed the brains of 20 deceased common bottlenose dolphins (Tursiops truncatus truncatus) that had been beached on the shores of Florida between 2010 and 2019.
Their analysis determined that the dolphins’ brains displayed dementia disease signatures. Not only that; it also demonstrated that some of the dolphins’ brains contained increased concentrations of certain toxins, such as 2,4-DAB, a substance that — according to some studies — could contribute to Alzheimer’s-like brain deterioration. Taken together, the results suggest that the stranded dolphins could have become confused around the shores before they beached themselves, just as dementia patients become disoriented around their surroundings, due to something similar to Alzheimer’s.
Read More: Dolphins and Whales Apparently Sleep With One Eye Open
The Threat of Algal Blooms
But where did the toxins in some of the dolphins’ brains come from? According to the team, algal blooms are a potential source, as 2,4-DAB is a product of cyanobacteria. Indeed, the team detected around 2,900 times more 2,4-DAB in the brains of the dolphins that beached themselves in the algal bloom season than they did in the brains of those that beached themselves outside the season. It is therefore possible, the team adds, that these dolphins’ brain damage and disorientation were intensified (as some dolphins’ brains do degenerate as they age on their own) by something as seemingly innocuous as cyanobacteria.
“Although there are likely many paths to Alzheimer’s disease, cyanobacterial exposures increasingly appear to be a risk factor,” said David Davis, a study author from the University of Miami’s Miller School of Medicine, according to a statement. “Since dolphins are considered environmental sentinels for toxic exposures in marine environments,” Davis added, “there are concerns about human health issues associated with cyanobacterial blooms.”
The team states that some studies show that concentrations of certain cyanobacterial blooms increase people’s chances of developing degenerative disease, too, meaning that the threat to dolphins is also a threat to humans.
Though additional research could add clarity to the cause of these strandings, and to the role of dementia and cyanobacteria in them, the results seem to stress that algal blooms are best avoided, for dolphins and for people alike.
Read More: Just How Intelligent Are Dolphins?
Article Sources
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