Cetacean intelligence

Cetacean intelligence

Brain size was previously considered a major indicator of the intelligence of an animal. However, many other factors also affect intelligence. Recent discoveries concerning bird intelligence have called into question the usefulness of brain size as an indicator.[1] Since most of the brain is used for maintaining bodily functions,[citation needed] greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks.[2][unreliable source?][3] Allometric analysis indicates that mammalian brain size scales at approximately the or http://www.packersnflofficial.com/Nike-Eddie-Lacy-Jersey.html exponent of the body mass.[4] Comparison of a particular animal's brain size with the expected brain size based on such allometric analysis provides an encephalization quotient (EQ) that can be used as another indication of the animal's intelligence.The encephalization quotient varies widely between species. The La Plata dolphin has an EQ of approximately 1.67; the Ganges River dolphin of 1.55; the orca of 2.57; the bottlenose dolphin of 4.14; and the tucuxi dolphin of 4.56;[9] In comparison to other animals, elephants have an EQ ranging from 1.13 to 2.36;[10]:151 chimpanzees of approximately 2.49; dogs of 1.17; cats of 1.00; and mice of 0.50.[11]The majority of mammals are born with a brain close to 90% of the adult weight.[12] Humans are born with 28%[12] of the adult weight, chimpanzees with 54%,[12] bottlenose dolphins with 42.5%,[13] and elephants with 35%.[14]The discovery of spindle cells (neurons without extensive branching, known also as "von Economo neurons", or VENs) in the brains of the humpback whale, fin whale, sperm whale, killer whale,[15][16] bottlenose dolphins, Risso's dolphins, and beluga whales[17] is another unique discovery. Humans, the great apes, and elephants, species all well known for their high intelligence, are the only others known to have spindle cells[18](p242). Spindle neurons appear to play a central role in the development of intelligent behavior. Such a discovery may suggest a convergent evolution of these species.[19]Elephant brains also show a similar complexity to dolphin Tramon Williams Kids Jersey brains, and are also more convoluted than that of humans,[20] and with a cortex "thicker than that of cetaceans".[21] However, in dolphins, "no patterns of Tramon Williams Jersey cellular distribution, nuclear subdivision, or cellular morphology indicate specialization of the LC (coeruleus complex)" despite the large absolute brain size and unihemispheric sleep phenomenology of cetaceans.[22] Moreover, it is generally agreed that the growth of the neocortex, both absolutely and relative to the rest of the brain, during human evolution, has been responsible for the evolution of intelligence, however defined. While a complex neocortex usually indicates high intelligence, there are exceptions to this. For example, the echidna has a highly developed brain, yet is not widely considered to be very intelligent.[23]Although many cetaceans have a great number of cortical neurons, after Homo sapiens, the species with the greatest number of cortical neurons and synapses is the elephant.[21](p73) All sleeping mammals, including dolphins, experience a stage known as REM sleep.[24] Unlike terrestrial mammals, dolphin brains contain a paralimbic lobe, which may possibly be used for sensory processing. The dolphin is a voluntary breather, even during sleep, with the result that veterinary anaesthesia of dolphins is impossible, as it would result in asphyxiation.[citation needed] Ridgway reports that EEGs show alternating hemispheric asymmetry in slow waves during sleep, with occasional sleep like waves from both hemispheres.[citation needed] This result has been interpreted to mean that dolphins sleep only one hemisphere of their brain at a time, possibly to control their voluntary respiration system or to be vigilant for predators. This is also given as explanation for the large size of their brains.[citation needed]Dolphin brain stem transmission time is faster than that normally found in humans, and is approximately equivalent to the speed found in rats.[citation needed] As echo location is the dolphin's primary means of sensing its environment analogous to eyes in primates and since sound travels four and a half times faster in water than in air, scientists[who?] speculate that the faster brain stem transmission time, and perhaps the paralimbic lobe as well, assist quicker processing of sound. (Though, if this is the case, it still does not explain the cause of the faster transmission time in the brain stem.)The dolphin's greater dependence on sound processing is evident in the structure of its brain: its neural area devoted to visual imaging is only about one tenth that of the human brain, while the area devoted to acoustical imaging is about 10 times[citation needed] that of the human brain. (This is unsurprising: primate brains devote much more volume to visual processing than those of almost any other animal, and human brains more than other primates.) Jordy Nelson Jersey Sensory experiments suggest a great degree of cross modal integration in the processing of shapes between echolocative and visual areas of the brain. River dolphins usually congregate in fairly small groups from 6 to 12 in number or, in some species, singly or in pairs. The individuals in these small groups know and recognise one another. Other species such as the oceanic Pantropical Spotted Dolphin, Common Dolphin and Spinner Dolphin travel in large groups of hundreds of individuals. It is unknown whether every member of the group is acquainted with every other. However, there is no doubt that such large packs can act as a single cohesive unit observations show that if www.packersnflofficial.com/Nike-Randall-Cobb-Jersey.html an unexpected disturbance, such as a shark approach, occurs from the flank or from beneath the group, the group moves in near unison to avoid the threat. This means that the dolphins must be aware not only of their near neighbors Jordy Nelson Kids Jersey but also of other individuals nearby in a similar manner to which humans perform "Audience waves". This is achieved by sight, and possibly also echolocation. One speculative hypothesis proposed by Jerison (1986) is that members of a pod of dolphins are able to share echolocation results with each other to create a better understanding of their surroundings.[30]Resident orcas living in British Columbia, Canada, and Washington, United States live in extremely stable family groups. The basis of this social structure is the matriline, consisting of a mother and her offspring, who travel with her for life. Male orcas never leave their mothers' pods, while female offspring may branch off to form their own matriline if they have many offspring of their own. Males have a particularly strong bond with their mother, and travel with them their entire lives, which can exceed 50 years. It is interesting behavior, as it may seem that there would be no benefit from this except perhaps in hunting techniques, although they could join other groups to hunt. There are two interesting examples of this familial bond in males. Two male sons, identified as A38 and A39, constantly accompany their mother A30, despite the fact that she does not need protection and they can all hunt by themselves, and rarely leave her side. Researchers have noted that if one son wanders away, one always remains with the mother. Another example are the brothers A32, A37 and A46, whose mother (A36) died. Instead of the family disbanding, the three brothers remain constantly together.Relationships in the orca population can be discovered through their vocalizations. Matrilines who share a common ancestor from only a few generations back share mostly the same dialect, comprising a pod. Pods who share some calls indicate a common ancestor from many generations back, and make up a clan. Interestingly, the orcas use these dialects to avoid in breeding. They mate outside the clan, which is determined by the different vocalizations. There is evidence that other species of dolphins may also have dialects.[31][32]In bottlenose dolphin studies by Wells in Sarasota, Florida, and Smolker in Shark Bay, Australia, females of a community are all linked either directly or through a mutual association in an overall social structure known as fission fusion. Groups of the strongest association are known as "bands", and their composition can remain stable over years. There is some genetic evidence that band members may be related, but these bands are not necessarily limited to a single matrilineal line. There is no evidence that bands compete with each other. In the same research areas, as well as in Moray Firth, Scotland, males form strong associations of two to three individuals, with a coefficient of association between 70 and 100. These groups of males are known as "alliances", and members often display synchronous behaviors such as respiration, jumping, and breaching. Alliance composition is stable on the order of tens of years, and may provide a benefit for the acquisition of females for mating. The complex social strategies of marine mammals such as bottlenose dolphins, "provide interesting parallels" with the social strategies of elephants and chimpanzees.[33](p519)Dolphins are known to engage in complex play behavior, which includes such things as producing stable underwater toroidal air core vortex rings or "bubble rings".[34] There are two main methods of bubble ring production: rapid puffing of a burst of air into the water and allowing it to rise to the surface, forming a ring; or swimming repeatedly in a circle and then stopping to inject air into the helical vortex currents thus formed. The dolphin will often then examine its creation visually and with sonar. They also appear to enjoy biting the vortex rings they've created, so that they burst into many separate normal bubbles and then rise quickly to the surface.[35] Certain whales are also known to produce bubble rings, or even bubble nets for the purpose of foraging. This was studied by Karen Pryor during the mid 1960s at Sea Life Park in Hawaii, and was published as The Creative Porpoise: Training for Novel Behavior in 1969. The two test subjects were two rough toothed dolphins (Steno bredanensis), named Malia (a regular show performer at Sea Life Park) and Hou (a research subject at adjacent Oceanic Institute). The experiment tested when and whether the dolphins would identify that they were being rewarded (with fish) for originality in behavior and was very successful. However, since only two dolphins were involved in the experiment, the study is difficult to generalize.