Tuesday, 16 June 2015


Dolphins just don't know when to shut up!

In fact they are almost making some kind of sounds. These are either about navigation and understanding their surroundings or about communication with other dolphins.  

Echolocation sounds are made in their nasal passages just below their blowholes, and are called clicks. Clicks are sometimes produced very close together and in strings. They sound like buzzes or chirps, and beamed forward from a special "lens" in the dolphin’s head. These sounds are produced behind the melon, an oily, slightly off-center lump that makes up the dolphin’s forehead. The sound waves are focused forward through it.

Scientists don't really know how the melon works, but it does seem to amplify and clarify the dolphin’s echolocation sounds. The dolphin's echolocation is so good that in one experiment, a dolphin located a marble-sized sphere at more than the length of a football field. 

Dolphins can produce high-pitched whistles and squeals in their larynx. These can rapidly change pitch in the same way we change the pitch in our voice. 
As far as scientists can tell, the whistles are a form of communication with other dolphins, and squeals are used to express alarm or sexual excitement.

Dolphin Communication

There have been lots of studies done to try to decide if dolphins actually have a language. Many of these studies have not been done very well and there are some extravagant claims that aren't supported by fact.

Others take the view that the dolphin's sounds are of no significance and that they are little more than fish. This point of view makes exploitation and even killing if these incredible mammals even more justifiable.

Most scientists feel that dolphins are highly intelligent. They have a greater brain-to-body-weight ratio (important in determining real intelligence) than any other mammal besides man. The appearance of the dolphin brain is similar to that of a human brain.They have brain ratios twice the size of any of the great apes. Some researchers place them in approximately the same category as our early humanoid ancestors. 

There is no doubt that dolphins communicate (like many other animals). We know that they communicate emotional states, danger, and the location of food. Their communication also seems to build group awareness within the pod.

But do dolphins actually have language?

The answer seems to be "yes". Dolphins tend to stay within their own pods, and may have trouble understanding outsider pods. In some studies individual dolphins appeared to have names. Dolphins used specific whistles in the presence of certain other dolphins. Different whistles were used with different dolphins as if calling them by name. 

While not proof, dolphins, like humans, take turns when making sounds as if information is being passed back and forth. Also like humans, dolphins use specific patterns in their "language".

Dolphins are indeed amazing mammals. Perhaps one day we will understand them better and be able to communicate with them. In the mean time they deserve our respect and a healthy ocean to swim in.

Thursday, 23 April 2015


Dolphins and Man-Made Sonar

Because of millions of years of evolution, dolphin echolocation abilities are much superior to those of any man-made device. For this reason, the US Navy have been studying them for years in order to improve their own sonar. What they've found has been surprising.

Dolphins are incredibly good at distinguishing their own echolocation sonar even in very noisy underwater environments – and in fact are very good at locating the drift nets that entangle and kill so many of them, raising the question of why they are still often trapped in them. It has also been found, though, that some noisy locations confuse dolphins, perhaps explaining why dolphins often ground themselves in areas where Navy ships using active sonar are performing maneuvers. 

Could the clumsier man-made sonar be using frequencies the dolphins associate with something else? Or perhaps it’s like looking into a strobe light for them. Whatever the explanation, the Navy is interested in eradicating the problem.

Dolphin Beaching
It’s the most tragic thing a dolphin lover can see: a pod of dolphins that have apparently killed themselves by swimming onto a beach and lodging themselves there. 

Why do dolphins do this?
The most prominent theory currently is that something confuses their echolocation, “blinding” them to the location of the beach in relation to the open ocean. Since many beachings happen near man-made sonar activity, it’s possible that this impacts them. 

 A pod of beached Pilot Whales

These bursts of man made 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.

Some very recent autopsies of beached dolphin bodies show a very high percentage of damaged hearing, suggesting that a very powerful sound somewhere may have basically blown out their hearing. Dolphins see quite well, but without their ears they are disoriented and blinded. And when one dolphin beaches itself, the others are at risk because they will try to help him.

However a beaching is initiated, it’s likely that it has much to do with how a dolphin perceives sound. Hopefully, we’ll soon understand enough about dolphin hearing to be able to prevent these tragedies.