Coming Ashore

November 5, 2001

Of Land and Sea
Two-thirds of our planet is covered by water. The teeming oceans are home to creatures great and small, from the exotic alien curiosities of the dark depths to the gleaming, swooping dolphins of shallower coastal waters.

Just as humans have evolved to live on land, so have ocean creatures evolved for life in the water. Even the ocean mammals that breathe air — such as dolphins and whales — must stay in the water to survive.

But some people walking along beaches have been astonished to find marine mammals lying on the shore, out of the water — sometimes in large groups. Seaworld, the popular marine park in Florida, notes that each year an average of 600-700 bottlenose dolphins gets stranded on the southeastern coastline of the United States alone.

Since dolphins and whales can't survive out of their element, what can possibly drive them to shore? To investigate, we spoke with marine veterinarian Jay Sweeney, who lives and works in California, about the phenomenon of cetacean strandings.

"There are two types of strandings," Sweeney explains. "The first is caused by illness or injury, and in such cases, strandings are usually solitary. The second kind is known as 'mass stranding', where a whole group of animals comes ashore, usually for very different reasons than those we attribute to individual strandings."

Meet Jay Sweeney
Veterinarian Jay Sweeney has a wealth of experience in dealing with marine life. Now in practice for 32 years, he has specialized in marine mammal medicine since the beginning of his career. He has published about 60 articles on the subject. Through his own consultancy practice, Sweeney has advised aquariums and oceanariums on dealing with strandings. He has also lead many rescue efforts for stranded marine mammals.

Individual Strandings
Humans are vulnerable to accidents in everyday life; so, too, are cetaceans. We worry about all kinds of hazards such as traffic accidents, fires, or hurricanes. Dolphins and whales also face a range of threats, from their natural ocean environment and from humans. "As far as injuries are concerned, just about anything can happen — particularly to animals that live along the coastline," Jay Sweeney explains. "Injuries result from impact with boats, shark bites, getting washed up on oyster beds, trauma from storms, and getting caught up in fishing nets."

Imagine what it must be like for a dolphin that has become incapacitated by injury. Unable to keep up with its cohorts, it will begin to wander alone. It may be too weak to swim against the currents and tides, and as a result, it may be carried to shore or farther out to sea. Where the dolphin ends up is purely a matter of chance, according to Sweeney. "In Southern areas, like the panhandle of Florida in the Gulf of Mexico, there tend to be more strandings. Certain areas have natural current eddies that tend to bring ill animals toward the shoreline." So, the tendency to get stranded on the shore is not the animal's specific response to injury; rather, it is an accident or "random event."

With this in mind, can there be any truth in the notion that sick and injured cetaceans come to shore seeking human help? Sweeney thinks not. "Some cetaceans, such as dolphins, have experience of interacting with humans. But I doubt that they would make the connection between human interaction and seeking assistance during infirmed states."

Sweeney elaborates by referring to the behavior of domestic animals when they are ill: "Pets often times do not seek the assistance of humans, even their companion masters, when they're sick. Typically they go off on their own. So there's really no reason to believe that cetaceans would have any desire to seek assistance from humans. That's why I believe stranding is random."

Clearly, there is no biological advantage to being away from the water; the best place for a dolphin or whale to be is in the water and not out of it. This fact supports the argument that strandings are accidental.

Cetaceans that are weakened by illness face a similar fate to those mammals hampered by injury. They are susceptible to the same kinds of problems as humans are, such as viral infections and intestinal disorders. (Seaworld notes that in 1990, an outbreak of morbillivirus lead to the deaths of about 750 striped dolphins in the Mediterranean Sea.)

Once cetaceans do contract an infection, they are immediately vulnerable to a secondary infection — of the lung. Take dolphins, for instance. "The dolphin's lung is very large," explains Sweeney (yes, dolphins have one lung and not two). "And the dolphin's nose is wide open. Dolphins don't have the natural filters that we have, and they breathe very rapidly, taking in large volumes of air. Generally with disease the immune system is compromised, and so the lung becomes very vulnerable. Consequently, most animals that come up on the beach have pneumonia."

Dealing with a stranding
What should you do if you encounter a stranded cetacean? The first thing to do is call the authorities. If you're not sure who to call, try the police. They will be able to find people who can care for the mammal properly. Do not try to push the mammal back to the water. Avoid interfering with it in any way, as this can cause further stress. Keep people and dogs away until professional help arrives.

Out of Their Element
When humans are immersed in cold water for too long, we lose body heat and suffer from hypothermia, a life-threatening condition. When whales and dolphins find themselves out of the water, they begin to generate too much body heat. They need water all around them to keep their body temperature in check. "Water is their only means of thermal regulation," explains Sweeney. "When these animals are stranded on the beach, they're frightened, stressed, struggling, burning a lot of calories, and generating a lot of heat — but they have no ability to dissipate that heat. They have a coat of blubber which protects them in the water, but which acts against them when they're on dry land. Their temperature rises rapidly, and it doesn't take long before the temperature gets so high that the damage to internal organs is irreversible. It's like going out into Phoenix, Arizona with a fur coat on. How long would you last? Not very long."

This immediate physical problem presents a great challenge to rescuers. Often times, rescuers arrive to find the animal still alive, but beyond saving. (Read about rescues in the sidebar to the right.) Dealing with the problem of overheating is tricky enough with a solitary stranded animal. But when there is an entire group, as in mass strandings, the problem becomes acute.

Coming to the rescue
Jay Sweeney has been involved in numerous rescues himself. "Every rescue situation presents its own challenges," he says. "The first thing we have to do is stabilize the animal's physical situation. If it's been washed up on the rocks, we move it from the rocks; if it's on dry sand and suffering from heat and dryness, we provide water. Some animals are very large and moving them requires trucks or forklifts with special harnesses. Generally speaking, small dolphins can be moved directly by one or two people if the animal is not struggling. We also have to make sure the animal is not being harassed by birds or dogs. Seagulls are particularly aggressive, but the presence of people is usually enough to deter them."

Mass Strandings
Mass strandings are perhaps one of the strangest and saddest phenomena of the natural world. In mass strandings, groups of cetaceans come to shore — sometimes in tens or even hundreds. "Mass strandings are a curiosity," says Sweeney. "We don't even fully understand why they occur." But there are a number of theories that seem reasonable.

It may be a simple matter of the ocean's powerful currents pushing groups of animals into dangerously shallow waters. Another possibility is that the sheer geography of some hunting grounds forms a natural trap for cetaceans. The Wellfleet area near Cape Cod is one such example:

Sweeney describes a possible scenario: "You'll get a group of pilot whales and they'll follow the fish into this area at high tide. They chase the fish into the shallow inshore space around islands and inlets. Then the tide goes out quickly. They aren't immediately left high and dry, but they're in dangerously shallow waters, so they get confused and can't find their way out. I believe that the animals get frightened because they see that their water is leaving them. They start to panic and vocalize, and they gather closer together — their natural reaction in the face of a threat. If one of them gets stuck on the sand, the tendency is for all of them to get stuck on the sand."

Certain species, such as pilot whales, false killer whales, sperm whales, and Atlantic white-sided dolphins, are more prone to mass stranding than others. These species are characterized by their tendency to gather in large groups. "That's part of their protective mechanism — there's safety in numbers," explains Sweeney. "It's generally believed that when they become stressed, or when there's a threat, their natural behavior is to aggregate, not separate." This explains why, when a group of any of these species runs into trouble, the group members stick together — and thus they all become stranded. There is no "every man for himself" philosophy.

This is demonstrated even more clearly when it comes to rescuing the mammals. Well-meaning members of the public have tried to push individual mammals back out to sea, only to find that they return to where the group is stranded. So, should you ever encounter a group of stranded cetaceans, resist your instincts to push them back into the water. The best use of your time is to seek professional help as quickly as you can. "The only action we can take is to bring them to a center where they can be treated," says Sweeney. "Then we can return them to the sea when they have recovered."

Read a CNN story from 1997 about whales that became stranded a second time as they tried to re-join their group.
This story from 1998 describes how 300 stranded whales died in New Zealand.

More Links
Veterinarian Jay Sweeney, who was interviewed for this story, works at Dolphinquest.

See how the Center for Coastal Studies in Provincetown, Massachusetts, assists whales in trouble.

Read about the Seaworld Rescue & Rehabilitation Program.

Cetacea.org provides a wealth of information on cetaceans.

Safely at Sea
Jay Sweeney has been part of many rescue efforts. When asked if the work is ever upsetting, he replies, "If an animal does not survive, it can be upsetting. But working with these animals is also inspiring. Most everybody is curious about dolphins, and I think that those of us who work with them feel lucky to be able to provide them with assistance." So, while sick or lost dolphins and whales may drift our way purely by chance, it is good to know that sometimes humans can be there to help them get back to where they belong, safely at sea.


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