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?




Wednesday, 9 April 2014

MEGALODON THE SUPER PREDATOR














Megalodon is a Greek name given to a now extinct giant shark that roamed the world’s oceans between about 2 and 25 million years ago. Megalodon literally means “big tooth”. It is the fossilized teeth that tell us much about what we now know was a ‘super predator’; the king of the oceans.


 


The teeth were so large that early finds were once believed to be petrified tongues of the dragons. 

Estimates vary, but we are confident that Megalodon grew to about 15 metres in length and quite possibly to 30 metres and was the largest shark ever to exist.


 
 Megalodon (gray and red) with the whale shark (violet), great white shark (green), and a human (black) for scale. Note: The maximum size attained by megalodon is indicated by the 20 m scale. Wikipedia


Scientists are certain that Megalodon preyed on whales, dolphins, and possibly giant sea turtles. Whale bones (including vertebrae and flippers) have been found with clear signs of large bite marks made by teeth that match those of Megalodon. Additionally, some geological excavations have found the giant teeth with the chewed remains of ancient whales.

 




In 2008 Dr. Stephen Wroe conducted experiments to determine the bite force of Megalodon. He found that very large specimens were capable of exerting a bite force of up to 275 Mpa (40,000 pounds per square inch); over 5 times greater than that of T. rex). 

Megalodon was probably the most powerful predator to have lived on Earth.





Most sharks are opportunistic; they will feed on a wide range of species and even scavenge for food. Some large sharks (including the great white shark which is a distant relative of Megalodon) attack their prey with great force. 

Their strategy is to inflict as much damage as possible and then follow their prey until it dies from blood loss. This not only saves energy but avoids the risk of injury in a fight to the death.



Scientists believe that Megalodon was no different than today’s big sharks. Fossil evidence shows that Megalodon attacked the larger whale’s flippers (with their large blood vessels) and the rib cage. In both instances the prey would have bled to death quickly.



Sharks like Megalodon have ‘sawing’ teeth that can carve out huge chunks of meat from their victims. 



 A reconstructed jaw of Megalodon shows the replacement teeth that would move up to maintain a sharp bite.


Megalodon’s jaws would have opened to a size of 2m wide and 2.3 m high. Its bite could have held as much as 5-6 m3 of flesh or about 6 tonnes of food.