Why do whales beach themselves? Are strandings increasing?

Darlene Ketten, a neuroethologist at the Woods Hole Oceanographic Institution, lays out an explanation:

I often use the analogy of a car crash: a lot of things can cause a crash, but you get the same end result. We can determine the cause of a stranding in only about 50 percent of all cases. In those, sometimes the cause is obvious, such as when a ship strike leaves an animal with distinctive fractures and gashes. In the northeastern U.S., pneumonia and trauma after storms are common reasons. We see other trauma as well, including shark attack or even assaults by members of the same species. Both human-derived pollutants and natural toxins, such as neurotoxins from algae, are implicated in mass strandings. Anomalies in magnetic fields and tsunamis have also been suggested as causes.

Some of the most fascinating cases stem from diseases and congenital conditions. We see parasites and pathologies far more severe than in domestic animals or humans. It is surprising that individuals can last as long as they do with such conditions.

Military sonars have clearly contributed to some recent strandings of beaked whales, but no evidence supports assertions that all whales are being affected by sonar. Interestingly, only beaked whales appear to be affected and only in a few locations—which offers hope of solving that problem at least.

Then there are cases with no single, clear answer. Diagnostic techniques common in human medicine, such as CT and MRI scanning and molecular studies, are now being used to improve insight into the causes.

We know of whale strandings dating back to the time of Aristotle, which implies that most are a natural phenomenon. That raises a question: If you insist on returning an animal to the sea, are you harming the population? If the animal is sick, what are we doing to that population pool? I’m not advocating failing to rehabilitate animals, if we can, but the issue is an important one to consider.

What to Do?

On the other hand, if a human activity precipitates a stranding, we need to know about it—to make decisions about pollutants, shipping routes and noise. Are we in some way contributing to declining health of critical populations, such as the northern right whale with fewer than 400 individuals left? We certainly have more reports of strandings, and people are looking into whether there are more instances or just more reports in some areas.

Sometimes, regardless of the cause, the only real option is to euthanize the animals—as was done in May after false killer whales that had washed onto land near Cape Town, South Africa, defied efforts to get them back out to sea. Imagine struggling to get those animals back in water in winter conditions. Though large, they are in some ways very fragile. For instance, if you get sand or water down their blowhole when handling them, the effect is like having water squirted up your nose. If you get the animal back into the water and it swims off but weakens and returns two or three times to shore, the decision will have to be made whether it can survive or is suffering, and a veterinarian must end its life humanely.

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