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)
From as early as the 17th 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?”
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