During Dan's online visit in the spring of 1997, he answered lots of questions from Scholastic Network subscribers about dolphins and about his research. Below is a transcript of those bulletin board conversations. Thanks, Dan!
What is the life span of dolphins?
Maximum life span is different from average life span. Some bottlenose dolphins may live to be 50 years old. Most don't. The average life span for a bottlenose dolphin is about 25 years. For most species of dolphins we don't know what the average or maximum life spans are.
How did you get interested in studying dolphins? How old were you when you first started studying dolphins?
It's hard to say why I got interested. Biological curiosity, I guess. I started studying dolphins when I was about 25.
What is the difference between a porpoise and a dolphin?
Basically dolphin teeth are cone-shaped and round in cross-section. Porpoise teeth are spade-shaped (like the spade in a deck of cards) and oval in cross-section. There are also differences in the skeletons. You can find out more at some of the suggested Web links.
What is the dolphin's favorite thing to eat?
Difficult to say because we can't ask the dolphins! Most eat fish and squid and sometimes shrimp. What they eat at a given time may depend on what kind of fish or squid is easiest to get.
We are a second grade class that is busy following the Ocean\Expo sailboat race from January to June. Our sailors are now in the Galapagos Islands. We would like to know what species of dolphins are in that part of the world. How different are they?
There are so many different species of oceanic dolphins that it is difficult to say what your sailors will see. Sperm whales, while not dolphins, are common around the Galapagos Islands. The sailors may see spinner dolphins, spotted dolphins, killer whales, false killer whales, pygmy killer whales, bottlenose dolphins, and who knows what else! Some are easy to tell apart and others are very difficult to identify, even for experienced observers.
What are the similarities/differences between dolphins and whales? What dolphins are found off New Jersey?
Dolphins are whales. In fact, the killer whale is just a big dolphin! Technically, the toothed-whale family Delphinidae contains all of the dolphins except the freshwater species. The real differences are between toothed whales (including dolphins) and baleen whales. For example, toothed whales have teeth and baleen whales have baleen. Toothed whales have one blowhole and baleen whales have two. A wide variety of dolphins can be found off New Jersey: bottlenose dolphins, pilot whales, killer whales, striped dolphins, whitesided dolphins, etc. Bottlenose dolphins are the most common near shore.
Why does the dolphin's skin feel slimy and rubbery?
While the bottlenose dolphin's skin may feel rubbery, it certainly isn't slimy. Dolphins don't have skin glands. Dolphin skin grows rapidly and is very flexible. It helps with streamlining.
Why don't dolphins have all those crusty barnacles on them like whales?
Actually, many species of dolphins do have barnacles, but of a different type than those found on the baleen whales. Lots of dolphins have soft barnacles on their flukes, fins, and flippers. Some beaked whales even have them growing on their teeth! I don't know why the hard barnacles grow on whales and not on dolphins. It may have something to do with swimming speeds as well as the speed with which a barnacle larva can attach to whale or dolphin skin.
What do dolphins smell like? I've never actually smelled one.
When they are dead they really stink! However, live dolphins don't have much of an odor because they don't have skin glands.
What do dolphins do to avoid their predators?
Dolphins have few predators to begin with. I would guess that whenever possible the dolphins will avoid predators rather than try to fight with them.
Is it possible that a dolphin can get caught in seaweed?
Dolphins play with lots of things, including seaweed. Seaweed includes a variety of aquatic plants. However, I've never heard of a dolphin becoming entangled in it.
When was the first dolphin discovered and where?
I don't know when the first dolphin was discovered. Probably no one knows.
Do dolphins sleep?
Yes, dolphins sleep but apparently not the same way that humans do.
Is anything that lives on land related to dolphins?
I believe that animals like deer and antelope are very remotely related to dolphins.
Why can't dolphins breathe under water? Why do dolphins have to live in the water?
Dolphins can't breathe under water because they don't have gills. They have lungs just like people and must breathe air. Dolphins have to live in water because they would overheat and dry out on land. Their bodies and body functions have evolved for life in the water.
Can dolphins understand human language? How do dolphins understand people?
Dolphins don't "understand" people as far as we know. Dolphins can not understand human language. Just like dogs and parrots, dolphins can be trained to respond to certain sounds or hand signals.
How many people are you working with? What other dolphins have you studied besides bottlenose?
I work on the dolphin project with four other people. I also study killer whales (which are really big dolphins), false killer whales, pygmy killer whales, spotted dolphins, spinner dolphins, Clymene dolphins, striped dolphins, Risso's dolphins, Fraser's dolphins and a few more.
How long do dolphins actually live?
It depends on which species you are talking about. Bottlenose dolphins may live for 50 years, but most only live for 25 years.
How long can dolphins stay under water without surfacing to breathe?
Bottlenose dolphins only stay under a few minutes on average. It depends on what they are doing.
How many times a day do dolphins eat?
Wild dolphins are opportunistic feeders. If food is available they eat because they don't know when the next meal will be.
How do you tell if dolphins are male or female?
You tell the sex of a dolphin by looking at the position of the genital slit on the belly. You have to be close to do this and it is not easy to do. The male's genital slit is closer to its belly button than the female's. However, if you are looking at adult killer whales it is easy to tell males from females because the males have a huge dorsal fin.
Why did you pick the bottlenose dolphin to study?
Bottlenose dolphins are common in the coastal waters of Florida and are easy to get to with a small boat.
When you are in the boat, how do you actually study dolphins?
We study the dolphins by taking pictures to identify individuals, by writing down the behaviors (like feeding) that we see them doing, by listening to their sounds, and by writing down when and where we see them.
Is it hard studying and following the dolphins? What is your favorite dolphin? Do you get attached to some of them? How long have you been working with dolphins? What is it like in the water with dolphins?
It is not necessarily hard to study dolphins but it takes lots of time and patience, especially when the weather is bad. I'm not sure that I have a favorite dolphin because I haven't seen them all. You can get attached to a dolphin just like you can get attached to a dog. I don't go in the water with dolphins, so I can't tell you what it's like.
Do you ever train dolphins by yourself?
No, I've never trained a dolphin. I like to stay with natural history studies and field work.
What is the difference between whales and dolphins? Why is the killer whale considered a dolphin?
All cetaceans (whales, dolphins, and porpoises) are considered to be whales. There are two kinds of whales: toothed whales and baleen whales. The toothed whales are broken down into several families. The family Delphinidae contains all of the "true" dolphins, including the killer whale. That is why it is considered to be a dolphin. However, common names can be confusing. One of the "true dolphins" is the pygmy killer whale, which is only about eight feet long. I guess that the common name used for an animal depends on the person who first described the species.
Are killer whales larger or smaller than elephant seals in Antarctica? What is the smallest whale known?
Killer whales are much larger than southern elephant seals. The smallest baleen whale is the pygmy right whale. The smallest cetacean is the harbor porpoise.
How big is a dolphin's brain compared with a human's?
The brain of the bottlenose dolphin is considerably larger than the human brain. After all, the bottlenose dolphin can weigh several hundred pounds. Big animals have big brains. Killer whale brains weigh about 6 kilograms (over 13 pounds).
Why are they called "killer whales"?
The killer whale probably got its common name because it kills other whales, dolphins, seals, and sea lions for food.
Can dolphins' size affect the way they swim?
Size probably does affect swimming ability. Small animals are more maneuverable than big ones.
How long can a dolphin stay out of water?
Dolphins may be able to stay out of the water for hours if they are kept wet and cool. They don't have sweat glands and have to keep their bodies in cool water to lose excess heat. One of the biggest dangers for stranded dolphins is overheating in the sun.
When looking for the dolphin fingerprints, do you ever have trouble identifying dolphins if they get new cuts, scratches, and nicks over or added to the old ones?
The nicks and scratches on a dolphin's dorsal fin can change dramatically over the years. That's why it is important to photograph them regularly. One of the advantages of freeze branding is that it is permanent and really doesn't change much over time. That's why people in South Carolina could recognize dolphin 56.
Do dolphins have taste buds?
Yes, dolphins do have taste buds.
How long do most dolphins live? Do you think keeping dolphins in captivity shortens their life span?
We don't know how long most dolphins live because we haven't studied them. For bottlenose dolphins, captivity seems to have no effect on life span compared with wild dolphins. We haven't kept the other species long enough to tell.
Do killer whales eat other dolphins? And if they do, why do they eat their own kind?
Yes, killer whales eat other whales and dolphins. They really aren't eating their own kind (cannibalism) because they are eating different species.
Do dolphins digest the entire fish, including bones?
Just about the entire fish is digested. First the meat and then the bones. About the only parts that aren't digested are the tiny ear bones. That is fortunate for us biologists because we use the fish ear bones to tell what kind of fish the dolphins have been eating.
How fast do dolphins swim? How far can dolphins travel before they have to take a break?
Some dolphins can swim 2030 miles per hour for short periods. However, most species haven't been clocked. Dolphins can probably swim for very long periods of time (certainly hours and maybe even days) if they are going slowly. But basically we don't know.
Do dolphins send out a warning when there is danger close by?
Yes, some dolphins do appear to make warning sounds.
Are you doing the research because there is a problem?
No, I am not doing dolphin research because there is a problem. I am doing it because I want to understand the biology of the bottlenose dolphin in the Indian River Lagoon.
What is the approximate population of the bottlenose dolphins?
Population of bottlenose dolphins where? In the world? We don't know. In the Gulf of Mexico there are thousands. In the Indian River Lagoon there are about 400.
How big are the dolphin babies?
Bottlenose dolphin calves are about 4 feet long when they are born.
Do dolphins leave the lagoon to die, and how old is the oldest living dolphin reported?
Dolphins do not leave the Indian River Lagoon to die. The oldest living bottlenose dolphin that we know of is 50 years old.
What happened to dolphins 55, 57, 58, 59?
To the best of my knowledge they are still in the Indian River Lagoon. One of the objectives of our photo ID project is to locate as many of the branded dolphins as possible.
Are there more males than females?
Unless you catch the entire population we can't tell what the sex ratio is. It probably starts out at one male to one female, but females probably live longer than males, and the mortality of young males appears to be higher than the mortality of young females. So, without actually knowing, I would guess that there are more females than males.
Do you have a personal favorite dolphin, or do you like them all?
I like them all, although dolphin 56 certainly is interesting.
How often do dolphins have babies? Do dolphins stay together for life?
How often a female dolphin has a calf depends on the species of dolphin and the condition of the dolphin population. If the population is stable (not growing) then the calving interval for bottlenose dolphins may be five to seven years. If the population is growing the interval may be two years. Bottlenose dolphins do not appear to stay together for life.
How far north could dolphin 56 go?
I really don't know how far north he could go. Easily to New Jersey and maybe into southern New England. A lot depends on water temperature.
What kind of food do dolphins feed their babies?
Dolphin calves drink milk from their mothers just like humans do. When they are about six months old they start eating fish. They probably learn this by watching their mothers feed. Dolphin mothers probably (I say probably because we don't really know) don't feed fish to their calves.
Why are dolphins so intelligent?
Lots of people think that dolphins are really smart but scientists don't have any information to prove it. Most dolphin biologists think that dolphins are about as smart as dogs and chimps. Posted by: Saveria Mazzola Subject: Dolphin Intelligence and echolocation You said that we don't know how intelligent dolphins are because we can't give them tests. The Kewalo Basin Marine Mammal Laboratory does cognitive studies with dolphins that have proven they are extremely intelligent. Their Web site address is http://www.dolphin-institute.com. They also have done extensive studies in echolocation. The studies show that dolphins can use their sonar to form "pictures" of the objects they echolocate on.
Is there a law that says not to kill dolphins anymore? What is being done to save dolphins?
In the United States all marine mammals (whales, dolphins, porpoises, seals, sea lions, walruses, sea otters, and manatees) are protected by the Marine Mammal Protection Act and some are also protected by the Endangered Species Act. Most whales and dolphins are not endangered. Those that are endangered have become so because humans have destroyed their habitat or affected their habitat in other ways.
Can dolphins have multiple births? What is the largest multiple birth on record?
The birthing process in whales and dolphins is called calving. Where we know about it, the number of calves born is almost always one. There are a few records of animals taken in whaling operations where there were two or more fetuses in the uterus. However, we don't know if they would have survived to birth. For a long time we thought that manatees only gave birth to one calf at a time even though some old records had documented twin fetuses. However, years of study in Florida have shown that manatees do occasionally have twins and that they can survive. Most whale and dolphin births are not observed, so we really don't know what happens. I suspect that twin births do occur, but only very rarely.
Why do dolphins swim along fishing boats when the people are not fishing?
Dolphins often ride the bow and stern wakes of all kinds of boats whether or not they are fishing. It is sort of like a free ride!
Can you identify dolphins by their squeaks and whistles from their sonar?
You can tell individual dolphins in the same species apart using their "signature whistles." The identification has to be done using electronic devices called sound spectrographs. You can also use the same machine to tell different kinds of dolphins apart based on the sounds they make. However, there are a lot of species of dolphins for which we do not have good recordings.
What is the biggest reason for dolphin death at sea?
For most species of dolphins the most common cause of death is probably natural disease. However, we don't really know what happens at sea, so we can't say for sure. However, for some species of dolphins the biggest cause of death may be entanglement in fishing gear like drift nets and purse seines.
Are there any forms of really rare dolphins that are in danger of extinction?
Yes, several species of dolphins and porpoises are in danger of extinction. The Chinese river dolphin, or baiji, is very close to extinction. So is the Gulf of California harbor porpoise. Some of the other species of river dolphins such as the susu and the boutu are also in trouble. However, most species of dolphins are not endangered.
Where do most of the dolphins prefer to live, and about how long can they live?
Dolphins live all over the world, from tropical to arctic waters. How long a dolphin lives depends on the kind of dolphin. We haven't studied them all so it is hard to answer the question.
Were the dolphins in the Indian River Lagoon spread out all over or were they in a certain area?
The dolphins in the Indian River Lagoon can be found throughout the length and breadth of the Lagoon. I'm sure that we will find that they prefer certain areas for feeding and other things.
Good-bye. It is time to say good-bye. It has been fun preparing field reports (even though we didn't get on the water very much!) and answering all of your questions. I'm getting ready to go to some scientific meetings in Europe and when I return I hope the weather in the Indian River Lagoon will be more favorable to field work. Dolphin 56? Yes, he's still out there and moving north. Today I got a report that he was seen yesterday in North Carolina!! Tune in to the
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