Who are dolphins?

Dolphins are marine or fluvial mammals. They belong to the cetacean order, to the odontoceti suborder (cetaceans with teeth), and to the delphinidae family of which included 33 species among which the killer whale we count.

The dolphin, a social animal

Most of dolphins live in pods ranging from 6 individuals as with the Tursiops, Tursiops truncates in coastal zone, up to thousands of individuals as with the pantropical spotted dolphin, the Stenella attenuata.

The led observations reveal a very high degree of social order. To Tursiops, the group, when it is consequent, is established by several subgroups.

·              the females and the young,

·              the sub-adults (sexually immature),

·              the adults male, often solitary and staying apart from the pod,

·              the dominant male(s) watching the group.

These various subgroups gather and separate throughout the day while occupying a vast territory ranging from 200 to 2000 square kilometers within which can be distinguished different areas dedicated to game, rest or hunting.

Birth and development

When a female gives birth for the first time, she usually joins generally her own mother’s clan  and raises her calf together with the other young, born in the same season.

The females are sexually mature at the age of 10-12 years, and they give birth to one calf at a time after 9 to 12 months of gestation. Generally, the future mother looks for the company of another female who will play ” the god mother ” role and assist her during the will intervene at the parturition. This godmother will help bring the newly born calf up to the surface to draw his first breath.

Amazing behaviors such as « baby-sitting » have also been observed: older females, sisters, or may be other members of the group, including an older male, have taken charge of watching over the young.  It has thus been possible to observe several dolphins setting up  an actual « playground» with the females positioned  in such a manner as to form a U with the young playing in the middle of it.

The young gradually leave their mother when they reach the age of three, but some have been found to stay with her until the age of 6 to 10. They then join a mixed group of teenagers within which they stay for several seasons. When reaching full sexual maturity, around 15 years old, males hardly ever come back to their native pod.

In the midst of teenagers’ groups, males of the same age establish close ties that can last a lifetime. When these males grow older, they tend to associate with a group of females.  The older males are often accompanied by two or three young until the end of their lives. This hierarchical organization shows a very high degree of social order in the dolphin’s culture.

Intelligence and communication

The size of cetaceans’ brain is large.  That of the dolphin weighs an average of 1.8 kilo (man’s weighs 1.5kg). Its complex structure is that of a thinking animal.  The dolphin’s great adaptability, his quick way to analyze problems and find solutions, and his hunting methods leave no doubt as to his intelligence.  However, as today, our understanding of the dolphin’s cerebral structures is still insufficient to fully measure  its potentiality.  On the other hand, we know that the higher the ratio between brain size and body surface is, the more developed is the capacity for intelligence and learning.  This ratio is 5.6 for the great dolphin, 7.4 for man, and 2.5 with the chimpanzee .

Dolphins hunt fish and feed on invertebrates with complex and varied techniques acquired through education5 which is an essential fact in the process of the evolution of « intelligence » in one species.

It would appear that the use of tools for feeding is not an unknown factor.  This has indeed been observed  with captive dolphins as well as with free dolphins.  In Australia, wild Tursiop  aduncus dolphins are said to be using marine sponges in order to protect their rostrum while they forage the sea bottom.

We have discovered only a minute part of the dolphins’ capacity to communicate but we can say that they are astounding. Various studies have proven, for instance, that young dolphins develop their own blow-whistle which could be used as their first name.

Dolphins death

When time has come, the dying dolphin is supported and raised so that he can breathe.  Dolphins take care of their injured and dying; an exceptional fact in the animal world.

  It is even more striking to note that dolphins would actually worship their dead, would understand the concept of death and would go as far as to perform a funerary « service ».

Researchers have noticed that dolphins appeared to have determined the origin of their baby’s death and were « discussing » it.