Creature Feature by Dr Gerald Goeden: Andaman sea

Showing posts with label Andaman sea. Show all posts

Friday, 18 April 2014

WILD DOLPHINS OF THE ANDAMAN SEA

There are approximate 25 species of Dolphins and each species has its own distinct personality and behaviors. Some of the species are easily kept in huge aquaria and it is there that we can learn much about these amazing animals. The Bottle Nose Dolphin is the most studied of all Dolphin species. We have about 6 species here in the Andaman Sea that show up regularly.

Bottle Nose Dolphins in an aquarium.

When traveling in the open ocean, Dolphins can cruise at 30 kilometres per hour. Scientists thought there must be something special about their skin. Now we know that Dolphin swimming muscles are very powerful and the high speed comes from lots of hard work. Dolphins also leap out of the water when swimming fast; they do this to increase their average speed and save energy.

Dolphins use a range of clicks, whistles, and squeaks to communicate with each other and to locate both prey and predator. Sending out sounds and waiting for their return creates a picture in the Dolphin’s mind similar to our sight. The process is called echolocation.

This Dolphin is using echolocation to find fish buried in the sand.

Clicks to home-in on a fish meal may be produced at 1,000 every second. When the prey is close some Dolphins use a very loud ‘pop’ to stun it and make the catching easier. With all that swimming a Dolphin eats about 10-15 kg of food each day.

A 'bait ball' of small fish is attacked by a pod of Dolphins. Schooling protects the fish but the Dolphins keen sonar will pick out an individual and follow it to capture.

Dolphins travel in groups called pods. Males spend a lot of time fighting with each other to determine who will be boss and get the best females for mates.

All of the males keep watch over the females so they can’t swim away to another pod. If they try to escape, they are bitten or hit by the males’ bodies. Of the 25 species, the Bottle Nose Dolphin is the most aggressive and will fight every day.

Dolphins do things we can’t understand. These Dolphins have learned to slide up onto the bank to eat the mud. Are they searching for minerals in their diet or does it just taste good? Because they learn by copying, they all use their right side and they have all worn down their right teeth. This has gone on for generations.

Being a Dolphin can be dangerous! Killer Whales and Tiger Sharks both prey on Dolphins. Seventy percent of wild Bottle Nose Dolphins carry some form of scars from fighting or escaping from predators.

A Killer Whale attacks a Dolphin and its calf with such force that they are thrown out of the water.

There is continuing debate over the ethics of keeping Dolphins in captivity.

On the one side, it's safe to say that there would probably be little protection of wild Dolphins today if some weren't kept where people could see them. Understanding brings protection in our world.

On the other hand, Dolphins are thinking, self aware, social animals that normally travel great distances every day. Is it fair to keep them in an artificial environment?

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Saturday, 21 September 2013

FROG OR FISH?

The weird Frogfish is a member of the family of fish known as the 'anglers'. They take their name from the ‘fishing equipment’ they carry on their head. The Frogfish uses a fleshy growth from its head (the esca (bait) and illicium (pole)) as a lure; the action of the growth attracts prey and is like angling.

Try to spot the blue eye, the orange mouth, and the white worm-like lure.

There are about 45 species of these strange, shallow water fish. They are mostly 10-20 cm long and are all benthic (bottom-dwelling) with foot-like pectoral fins. The Frogfish uses these ‘feet’ to walk across the ocean bottom instead of swimming. If they are in a hurry they use jet propulsion by squirting water out of their small gill openings.

Frogfish are ambush predators; they rest motionless in the coral or on the bottom using their built-in camouflage. They are able to adjust their color to blend in with their surroundings. Others have outgrowths of skin that look like sponge or seaweed.

When prey are near, they ‘wiggle’ the worm-like growth on their head attracting their next meal. They have huge heads and mouths and can swallow fish half their size. The snapping action of their jaws is triggered automatically when the lure is touched.

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Tuesday, 9 July 2013

SWIMMING WITH TIGERS by Dr. "Gerald Goeden"

There is much concern about shark fishing and shark fining. Ocean conservation is at stake as predators in all the world oceans are subjected to over-fishing. Caribbean and Andaman Sea fisheries (Malaysia) are especially stressed. Growing support for eco-tourism based experiences like swimming with sharks and swimming with dolphins promise to outstrip the economic benefit of over-exploitation. The following report looks at the experience of one of our scuba divers in assessing a shark conservation project off South Africa.

During a recent photo expedition Jeff had a surprise visit from a big Tiger Shark. Jeff and Gerry tell the story:

“All of a sudden something was holding on to my scuba gear and shaking me like a feather. I was so busy getting some great shots that I didn’t see this big one come up behind me.”

“I was pretty lucky that I wasn’t hurt, but it seemed like the Tiger was just trying to figure out what I was.”

The Tiger Shark, which generally hunts at night, has a reputation for eating anything and everything and for an aggressive nature. Most of the time, Tiger Sharks eat fish, squid, seabirds, sea mammals, other sharks, and turtles.

Out of more than 360 shark species, only four have been involved in a significant number of fatal attacks on humans over the last 60-70 years: the great white, tiger, oceanic white tip, and the bull shark. Culling Tiger Sharks a few days after an attack probably has little value since most are nomadic and the offending animal may well move on. Some governments ‘protect’ swimming beaches with shark nets that catch any sharks swimming along the coast.

Even small Tiger Sharks require a lot of watching and big ones can weigh up to 1000 kg and reach 6-7.5 metres. They get the name Tiger from the vertical stripes and not from their diet. Based on diet, they are more like ‘trash-can sharks’ since stomachs have been found to contain buckets, rolls of wire, gas cans, paint brushes, and baseballs. One even contained old tires.

So why did the shark bite Jeff’s metal air tank?

First, the shark was confused by the metal on Jeff’s back. Tiger sharks have small pits (ampullae of lorenzini) on their snout and along their upper bodies which can sense weak electrical fields. Normally these sensors detect fish when the water is too murky for their usually sharp eyes to see. But different kinds of metals generate weak electric currents in seawater and alert the shark that something is going on.

Secondly, the Tiger Shark’s keen sense of smell would not be sure if the smell of human meant the next meal or danger. You don’t grow up to be a big shark without a little caution!

Finally, sharks adopt the same strategy as children; if you are unsure what something is, just put it in your mouth and taste it.

“Diving with Tiger Sharks is awesome and something I will never forget. The footage will be great for documentary work and we always learn something about these incredible animals. We have to work fast as Tiger Sharks are disappearing because of the shark fin trade and sport fishing.”

Nature has equipped these sharks with all the gear to be great hunters: they can sense movement in the dark, feel water pressure waves from injured animals, smell traces of blood in the water, and have excellent vision. They are fearless and haven’t learned to stay away from boats and fishing gear.

Thursday, 20 June 2013

DOLPHIN INTELLIGENCE by Dr Gerald Goeden

Dolphins are found throughout most of the world oceans. Here in the Andaman Sea we are lucky enough to have 9 cetaceans:

Indo-Pacific finless porpoise (Neophocaena phocaenoides)
Indo-Pacific humpback dolphin (Sousa chinensis). Also known as the Pink Dolphin or White Dolphin.
Irrawaddy dolphin (Orcaella brevirostris)
Indo-Pacific bottlenose dolphin (Tursiops aduncus)
Long-beaked common dolphin (Delphinus capensis c.f. tropicalis)
Gray’s spinner dolphin (Stenella longirostris)
Pantropical spotted dolphin (Stenella attenuata)
Bryde’s whale (Balaenoptera edeni)
Dugong (Dugong dugon)

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?”