Dr Gerry Goeden's Swimming With Dolphins: humpback whale

Showing posts with label humpback whale. Show all posts

Friday, 6 December 2013

The Origin of Whales and Dolphins

Whales and dolphins belong to a group of animals called cetaceans. All cetaceans live in water today but their ancestors were land animals.

The closest relative to today’s cetaceans is the hippopotamus. Whale ancestors left the land about 50 million years ago and became the baleen whales (plankton feeding) and toothed whales (fish and squid eaters) of today.

Humpback Whales

What did the early whales look like and how did they live?

The first fossils were found in the

United States

and were so different from modern whales that they were described as a reptile (dinosaur). Because of their size, they were named Basilosaurus, or king lizard. Many fossils were found with an average length of 18 metres and scientists believed that they may have reached 45 metres. Fossils have been found in Pakistan and

Egypt

and may have given rise to early worship of crocodile-like gods.

They were so different from modern whales that they were described as a reptile (dinosaur).

But they weren’t lizards!

We now know that the fossil Basilosaurus was a whale that probably hunted in shallow seas between 34 and 40 million years ago. It was about 18 metres long and the biggest animal on Earth at that time.

It had small paddle like hind fins that were left over (vestigial) from what were once legs. They were so small that the Basilosaurus probably swam more like a snake than a modern whale.

We can be very certain (look at the teeth) that Basilosaurus was an aggressive and dangerous predator. Careful examination of the skeleton suggests that Basilosaurus may not have been a long distance swimmer and probably could not dive to great depths. Its head and teeth are reminiscent of a crocodile’s and it may have hunted in a similar way; surprise attacks in shallow water or swimming down unfortunate prey.

Another 30 million years of evolution finds us sharing the planet with 81 species of whales from the metre long Hector’s dolphin to the Blue Whale, the largest animal to have ever lived on Earth.

Blue Whale and its calf

Killer whales in a pod.

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Sunday, 15 September 2013

SONAR AND WHALE STRANDINGS

I was recently speaking with a group of students visiting from Mexico when one asked, "Why do whales beach themselves?" The answer isn't an easy one!

Sonar comes from the contraction of the phrase, ‘sound navigation and ranging’. In more technical terms active sonar is the use of sound sent out into the water and then reflected to determine the location of an object. Passive sonar makes use of listening for sounds and triangulating their source. The development of sonar was for military purposes but a co-researcher of mine uses passive sonar (does not emit sound) for location, counting, and identification of whales.

Does sonar cause whale strandings?

Two thousand years ago Aristotle wrote: “It is not known why they sometimes run aground on the seashore; for it is asserted that this happens rather frequently when the fancy takes them and without any apparent reason'.”

Clearly there have been reasons for whale strandings before the advent of military sonar. This does not prove that military sonar is not responsible for some of the strandings today.

When active sonar is used an intense burst of sound is released underwater. These sweep the ocean like a floodlight, revealing objects in their path as echoes return to the source.

French F70 frigates are fitted with VDS (Variable Depth Sonar) type DUBV43 or DUBV43C towed sonar

These bursts of sound can reach 240 decibels (billions of times more powerful than the level that causes hearing damage in humans). During testing off the California coast, noise from one of the Navy's low-frequency sonar systems was detected across the full width of the northern Pacific Ocean.

How Sonar Harms Whales

By the Navy's own estimates, even after 500 kilometres, these sound bursts can retain an intensity of 140 decibels -- a hundred times more intense than the level known to affect the behavior of large whales.

Many of these beached whales have suffered physical trauma, including bleeding around the brain, ears and other tissues.

A 1986 West Australian stranding of False Killer Whales

These injuries are similar those resulting from underwater explosions or barotraumas (injury from pressure). I have seen these injuries and provided forensic evidence in legal cases dealing with underwater explosives. They found that many more animals were affected, injured, or chased from the area. Scientists are concerned about the cumulative effect of these bursts of sound on marine animals.

“The Navy’s most widely used sonar systems operate in the mid-frequency range. Evidence of the danger caused by these systems surfaced dramatically in 2000, when whales of four different species stranded themselves on beaches in the Bahamas. Although the Navy initially denied responsibility, the government's investigation established that mid-frequency sonar caused the strandings.” according to the Natural Resources Defense Council. Similar mass strandings have occurred in the Canary Islands, Greece, Madeira, the U.S. Virgin Islands, Hawaii and other locations.

Can we build less dangerous sonar?

It is possible to build sonar systems that use frequencies or power levels that will not harm whales. The problem is that we are ethically unable to carry out research that would deliberately harm whales so we can measure the effects. We can not have controlled exposure experiments because at least 20% of the test animals would have to be stranded, injured, or die to meet statistical analysis requirements.

A Supreme Court decision in the U.S.A. (2000) stopped the U.S. Navy from testing powerful sonar systems in most of the world's oceans after a federal judge ruled that it could "irreparably harm" whales, dolphins and fish. This decision does not relate to other Navies.

The other issue has to do with military competition and security. Supporters of more powerful sonar will claim that we are putting whale safety ahead of national safety if we limit what only some countries can test.

Humpback whales are among the marine mammals effected by sonar.

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Thursday, 1 August 2013

AMAZING DOLPHIN ECHOLOCATION by Dr. Gerry Goeden

Dr. Gerry Goeden is a marine biologist working in the Andaman Sea.

When the mammalian ancestors of whales began to move from land and back into the sea they were faced with huge problems. A major difficulty was that they had lost the evolutionary advantages necessary for a successful aquatic life; underwater vision was difficult, they were poor swimmers, and they were easy prey for the huge sharks that inhabited the ocean from 50-75 million years ago. In fact, sharks may have been their greatest problem since sharks had already perfected incredible senses of smell, sound detection, and the ability to receive the invisible electrical fields produced by other animals. Not only were the sharks more efficient fishermen but large sharks could detect, out-swim, and then capture ancient whales.

Many whales solved this problem with the help of evolution by becoming so large that even large sharks couldn’t eat them. They also stopped competing with sharks for food by changing to a plankton diet. Their descendants are the baleen whales of today: examples are the Right Whale, Gray Whale, and Humpback Whale.

Other whales evolved to compete with the sharks. They retained their teeth and fish diet but became faster and developed an incredible sense of echolocation which allowed them to ‘hear’ the approach of huge sharks long before they could be seen.

Because sound travels through water better than light does, the ability to make a sound and then interpret the ‘meaning’ of its echo, allowed the toothed whales to find food when sharks couldn’t and avoid predators before they could get too close. Whale echolocation today may be the most sophisticated sensory system in the entire animal kingdom. Unlike our own vision, echolocation for whales carries three dimensional information. Toothed whales can ‘see’ inside and through many objects and reflected sounds seem to allow them to ‘see’ around or behind things.

The information that can come back by echo depends on the frequency of the sound. Low frequency travels long distances and has less detail while high frequency is shorter range with high definition. To get the whole picture some whales ‘sweep’ the frequency range between high and low frequencies. When they home in on prey these ‘sweeps’ sound like a continuous creaking sound.

When humans send out radio signals for locating things (radar), we focus the signal into a beam using a specially shaped antenna. Toothed whales do the same with sound using special fat deposits in the top of their heads and in their jaws. This fat is different from the other fat deposits in the whale’s body and fits into specially shaped areas in the jaw and skull. We use facial muscles to frown or smile but whales seem to use their muscles to adjust the shape of the fat deposit and focus the sound beam.

These special fat deposits are most remarkable in the sperm whale where they may weigh several tonnes. In dolphins the deposit looks like a rounded lobe on the front of the head and is called the melon.

The frequency of toothed whale sounds ranges from 40 Hz to 325 kHz. A list of typical sound levels is shown in the table below (from Wikipedia). A level of 120dB causes hearing damage and pain in humans.

Kind of Whale	Sound	Broadband level (dB)
Sperm whale	clicks	163–223
Beluga whale	echolocation clicks	206–225
White-beaked dolphin	echolocation clicks	194–219
Spinner dolphin	pulse bursts	108–115
Bottlenose dolphin	whistles	125–173

We still don’t know much about all this whale engineering but it seems to work like this:

A powerful sound is generated by ‘vocal cords’ (phonic lips) within the whale
As the sound radiates out, the melon focuses it like a lens focuses a beam of light
The sound beam hits an object in the sea and is reflected back
The teeth in the lower jaw act as ‘antennas’ collecting the echoes
Fat deposits in the lower jaw carry the sound to the inner ears
The complex brain interprets the echoes and constructs a ‘picture’ of the object

In this way a whale may see a picture with sound similar to the picture we see with light. It is clear though that the picture is only as good as the information processor that untangles the complex echoes coming back to the whale. To see with sound, whales have also evolved very large brains.

Many people believe that the large brain means that dolphins in particular are the philosophers of the sea. The truth is that a large part of that brain seems to be used for processing and remembering echo information necessary for feeding and navigation and relating to other whales with their own acoustic information.

The ancestors of whales had ears for hearing on land. Whales still have ear openings that lead to the inner ear. In baleen whales these openings are filled with a hard wax but in the toothed whales the hole is open. There is evidence that dolphins can hear in air and water with these openings but they probably play a very small part in echolocation.

The baleen whales are not hunters like the toothed whales and have not developed the elaborate clicks and whistles to ‘sweep’ their prey. It has been suggested that baleen whales may use their stored echo-soundings to create complex three-dimensional maps of the ocean floor thousands of meters below for use in their long annual migrations covering tens of thousands of kilometers.

Illustrations are from Wiki-commons.

Tuesday, 9 July 2013

DOLPHIN INTELLIGENCE by Dr Gerry Goeden

There are many times that dolphins have rescued swimmers or fought off attacking sharks at real risk to themselves. Because of these actions, humans tend to feel there is a special bond between dolphins and themselves and that this bond is based on mutual intelligence or a wished for understanding.

From as early as the 17^th century scientists have been impressed by the size of dolphin brains and rated them near the top of the ‘non-human’ intelligence list. Many cetaceans (whales) do have large brains and, relative to body size, toothed whales have larger brains than baleen whales. In fact, the relative brain size of bottle nose dolphins is nearly the same as that of humans. Dolphin brains range from about 0.25% to 1.5% of their body weight and human brains are about 1.9% of our body weight.

Another measure of brain development is based on the number of folds in the grey matter (cerebral cortex). This is the part of the brain that gives us conscious control of our bodies and thoughts. Toothed whale brains have more folding than baleen whales but much of this is taken up for sound production and processing. Toothed whale brains, like the dolphin’s, have folding that resembles that of hoofed animals like horses and deer.

We don’t know if dolphins have a language but we do know that they share information about their surroundings, their emotions, and their identity through acoustic whistles and clicks.

Memory experiments with dolphins showed that their picture of the world and their ability to remember it was better when based on their sonar and not so good when based on sight. Their memory was best when they could use sonar and sight together.

Dolphins have also been taught ‘words’(using hand signals) that can be put together in two-word sentences like “get ball”. Scientists found that they understood these sentences about 80% of the time. Able to grasp the basics of human language, it may be possible to communicate in two and three word format with dolphins in the future. If we do decide to talk with dolphins it will be best to choose our subjects wisely since research shows a large variation in ‘intelligence’ among species.

We think of intelligence as the ability to understand our surroundings and process information so that we can react in the most favorable way. In this way intelligence is not the same as instinct where reactions are ‘pre-programmed’ in the brain. In the animal kingdom, species with higher intelligence tend to be social animals that live in groups.

It is thought that the evolution of intelligence is related to the need to understand group dynamics and the individual’s place within them. The ‘smarter’ dolphins operate in social structures similar to dogs and primates.

Having a well developed brain and intellect; humans are always quick to make lists showing the relative intelligence of other animals with us at the top. To be fair, we must always ask the question: “How intelligent would we be in the dolphin’s world of sound and social behavior; in a world without landmarks and signs; and without shelter and an organized food supply?”

Tuesday, 21 May 2013

DOLPHINS IN CAPTIVITY

One of my best friends over the years was a marine mammal veterinarian. He looked after the health of animals like dolphins, sea lions, and whales while they were in captivity. A great but very controversial job!

Because all of the marine mammals are fairly intelligent, they require stimulating environments. Over the years many people have come to believe that being held in captivity just doesn’t meet those requirements and that these ‘more cognitive’ animals need to lead more acceptable and ‘freer’ lives.

We often talked about the pros and cons of marine mammals in captivity; and yes, there are pros and cons but these seem to be shifting toward the negative and so collecting and moving marine mammals is now very difficult. Most new additions are offspring of those kept in captivity for many years.

Let’s look at the arguments.

First let’s look at some of the biological questions;

Q. Dolphins eat fresh food in the wild but in captivity, they have to eat frozen seafood. Does that affect the dolphin's health?

A. Dolphins are aggressive predators and spend as much as half of their time hunting. In captivity, they don't have to do this and miss out on some of their behavior. 'Fish' is frozen not only to make it easier for aquariums to store but to kill parasites that invade the dolphin's digestive system in the wild. Frozen seafood is also supplemented with vitamins and minerals. Dolphins are too expensive for aquariums to risk their health because of bad food. I would say that they eat as well or better in captivity.

Q. How big would a tank have to be to keep dolphins in captivity?

A. This is a difficult question because in the wild, there really aren't any border; dolphins can go where they like and travel great distances. In the wild they can swim up to 200 km a day and some species spend much of their time in very deep water. Others like the Chinese Humpback dolphin don't move around much in the wild and stick to the familiar surroundings.

Q. Are dolphins physically stressed when they live in captivity?

A. Dolphins are highly intelligent animals and live in complex social groups. It is argued by aquariums that dolphins live longer in captivity due to less disease and predation. " Pro-dolphins groups argue that they live longer in the wild because they lead more natural life and belong to social groups. Stress and odd behaviors are sometimes seen in dolphins held in aquaria but then they aren't subject to shark attacks and parasites either.

Q. Is it a good idea to put different 'kinds' of dolphins in the same tanks?

A. Captive dolphins often come from different regions and populations. While wild dolphin groups do stick together, there is quite a lot of movement of individuals between groups. If this were not so then dolphins would quickly become inbred and genetically weakened.

Dolphins in captivity sometimes share tanks with other marine mammals but this is avoided by better aquariums. Competition and fighting between species damages the animals and my friend's medical work was very expensive.

Now lets look at some of the ethical questions that relate to keeping intelligent animals in captivity;

Q. Do dolphins enjoy performing in shows?

A. Because of their intelligence and social nature they do enjoy challenging activities (performing). Most of the performance behaviors are based on their natural behaviors and dolphins will not do them if they don't feel like it. They literally go on strike. Left alone, they will play with balls and hoops just as they will play with debris and seaweed in the wild. Another question could be "Do dolphins prefer to play with balls in captivity or seaweed in the wild?" My guess is they would find the wild much more interesting.

Q. Dolphins and other marine mammals have very large brains so are very intelligent. Do they suffer mentally in captivity?

A. The Indo-Pacific Bottlenose Dolphin (Tursiops truncatus) has an absolute brain mass of 1500 - 1700 grams. This is slightly greater than that of humans (1300 - 1400 grams) and about four times that of chimpanzees (400 grams). They are intelligent but most of that brainpower goes to processing underwater sound and echo-location. Our best estimate is that they are of similar intelligence to elephants and some apes. So, yes, they would suffer if they didn't get a stimulating environment. we don't know if they long for the wide open spaces.

Q. Are dolphins forced to live in mentally stressful situations?

A. While aquariums do their best to remove stress, the fact is that limited space and social interactions take their toll. Dolphin males spend a lot of time fighting over females and the loser finds it easier to get away in the wild; there can be more damage through continued aggression in aquaria IF the managers don't keep competing animals apart. Unnatural social relationships are probably the biggest mental problem faced by dolphins in captivity.

Q. Would dolphins escape if they could?

A. An interesting question. The U.S. Navy uses dolphins to search the bottom of ships for explosives, locate mines in harbours, and ‘spot’ enemy divers. The dolphins are released from captivity and go off to do their jobs. When they are finished they return to captivity.

My friend, the marine mammal veterinarian, says that like dogs dolphins build bonds to humans and see us as their ‘family’. And like dogs they come home after they have been released.

Have a look at some of the photos of his work with dolphins.

Prior to 1980, more than 1,500 bottlenose dolphins were collected from the United States, Mexico, and the Bahamas, and more than 550 common and 60 Indo-Pacific bottlenose dolphins were brought into captivity in Japan. By the late 1980s, the United States stopped collecting bottlenose dolphins and the number of captive-born animals in North American aquariums increased from only 6 percent in 1976 to about 44 percent in 1996. It is well over 50 percent now.