The creatures that live on the Earth, from any species and group, generally have common emotions and feelings that are closely related to their brains’ size and biological statuses. The biological statues of any creature is directly affected by the way they show their emotions, how they love, how violent they are and how they communicate with the surrounding world. Additionally the territory is of great importance. Among marine creatures Dolphins have special characteristics. They intercourse and get pregnant; after giving birth they feed the dolphin calves with milk. This aquatic got accustomed to living in water over millions of years. Their staple foods are fish and cephalopods. Due to Their brains’ function in comparison to other marine mammals; they can store memories in their short term memory and long term memory. This ability makes them social so that they can live in groups with different number of members. Group life of dolphins arose from their need for decreasing the possibility of getting hunted by “enemies”. They also show some signs of “culture”. Choosing an “opposite-sex” mate from other groups sometimes makes dolphins aggressive. They often are polygamous. Their genitals are located on lower part and end of their bodies. They intercourse by sticking their bellies together and this could be done several times in a short while. One of the most significant behavior of dolphins is their suspicious suicide. Depression, generational shift by old dolphins, marine pollution, military and non military ships traffic and many other nonscientific reasons are counted among the possible cause or causes of this phenomenon. What matters about dolphins’ death is that they wash up on beach dead not alive, it is certain that dolphin species goes extinct, but scientists haven’t declared a definite time for that .