'Calves are born without spots which increase with age. The main problem for this particular species of dolphin still remains with the incidental take in the Eastern Tropical Pacific through the tuna fishing industry. Purse-Seiners set their nets around the dolphins since they are the reliable indicators of the presence of yellowfin tuna. Unfortunately the dolphins occasionally get caught in the net and being mammals that need to surface to breathe, they simply suffocate and drown. Japan also has a directed fishery for this species for human consumption, where they take around 1,000 individuals each year as part of its harpoon fishery.

Here's how a dolphin finds there food

1.1- How do dolphins sleep? Dolphins have to be conscious to breath (Williams et al, 1990). This means that they cannot go into a full deep sleep, because then they would suffocate. Dolphins have "solved" that by letting one half of their brain sleep at a time. This has been determined by doing EEG studies on dolphins. Dolphins sleep about 8 hours a day in this fashion. REM (Rapid Eye Movement) sleep, usually associated with dreaming has been recorded only very rarely. Some scientists claim dolphins do not have REM sleep at all. A dolphin's behavior when sleeping/resting depends on the circumstances and possibly on individual preferences. They can either: - swim slowly and surface every now and then for a breath - rest at the surface with their blowhole exposed - rest on the bottom (in shallow water) and rise to the surface every now and then to breath. sources: S.H Ridgway (1990) The Central Nervous System of the Bottlenose Dolphin, in S. Leatherwood and R.R. Reeves: The Bottlenose Dolphin, pp. 69-97, Academic Press Th.D. Williams, A.L. Williams and M. Stoskopf (1990) Marine Mammal Anesthesia. In: L.A. Dierauf (ed.): Handbook of Marine Mammal Medicine: Health, Disease and Rehabilitation, pp. 175-191 CRC Press, Boca Raton 1.2 - How intelligent are dolphins? The short answer to this is that we do not know. There is no reliable method to measure intelligence in humans across cultures, so it is not surprising that comparing humans, dolphins, apes, dogs, etc. is impossible. There are some indications of their potential: they are fast learners and can generalize (which is also true of pigs, BTW). Also they can learn to understand complicated language-like commands (which is also true of the great apes). 1.3 - How do dolphins communicate and do they have their own language? Dolphins communicate mainly by means of sounds. These sounds include whistles, but also so-called pulsed sounds, which are often described as squawks, barks, rasps, etc. But they also use breaching (jumping and falling back into the water with a loud splash) and pectoral fin (or flipper) and tail (or fluke) slaps (hitting the flipper or fluke on the water surface). Body posturing and jaw popping also have a role in communication. This list is not exhaustive. As for language, we do not know if they have one. Several studies have demonstrated that dolphins can understand a structured language like ours. This same has been demonstrated for a number of other animals species as well (gorilla, bonobo, California sea lion, parrot).

Some studies also indicate that dolphin vocalizations are complex enough to support some form of language. However, to date it has not been demonstrated yet that they indeed use a language for communication among themselves. 1.4 - How does dolphin sonar work? Dolphins (and other toothed whales) can produce high pitched clicks. When these clicks hit an object, some of the sound will echo back to the "sender". By listening to the echo and interpreting the time it took before the echo came back, the dolphin estimate the distance of the object. (That's why sonar is also called echolocation: with information from the echoes, a dolphin can locate an object). Depending on the material the object is made of, part of the sound may penetrate into the object and reflect off internal structure. If the object is a fish, some sound will reflect off the skin on the dolphin's side, some of the bones, the internal organs and the skin on the other side. So one click can result in a number of (weaker) echoes. This will give the dolphin some information about the structure and size of the fish. By moving its head (thereby aiming the clicks at other parts of the fish) the dolphin can get more information on other parts of the fish. It is like a medical ultrasound probe, but the results are far less clear. A medical probe moves back and forth very rapidly, much faster than a dolphin can move its head. Also the frequency of the sounds of the medical probe is much higher than a dolphin's sonar. Therefore the level of detail the echoes can provide is much higher in the medical probe. For technical information on dolphin sonar, check out the following book: W.W.L.Au (1993) The sonar of dolphins. (Springer-Verlag New York). 1.5 - Can dolphins combine information from their sonar with their vision? The short answer is: yes, they can. Just like people can visualize an object by just touching it, dolphins can get an idea of what an object looks like by scanning it with their sonar. They can also identify objects with their sonar that they have only been able to see. If they form a visual picture from the sonar information (visualization) or form an acoustical picture from visual information is still unresolved. This capability is called cross-modal transfer and it has been demonstrated in only a few animal species so far: the bottlenose dolphin and the California sea lion. See the following references for more details on this subject. R.J. Schusterman, D. Kastak and C. Reichmuth (1995) Equivalence class formation and cross-modal transfer: testing marine mammals. In: R.A. Kastelein, J.A. Thomas and P.E. Nachtigall (eds): Sensory systems of Aquatic Mammals, pp. 579-584 De Spil Publishers, Woerden, the Netherlands ISBN 90-72743-05-9 A.A