The mammalian order Cetacea is composed of two parvorders, the Odontoceti (toothed whales) and the Mysticeti (baleen whales). They compromise of over 80 known living species of whales, dolphins and porpoises (Reiss & Marino, 2001; Simmonds, 2006). The compelling sets of characteristics they have acquired over their 55-60-million-year evolution including echolocation ability and complex social organisation (Hof, Chanis, & Marino, 2005) have created great belief that this order contains some of the most intelligent animals (Simmonds, 2006), with the suggestion that they are second to humans in terms of general intelligence (Reiss & Marino, 2001).
Modern cetacean brains are among the largest of all mammals in terms of both general size and in relation to body size, with the largest brain in the animal kingdom being possessed by the sperm whale (Physeter macrocephalus) (Marino, 2004) with a mass of 60% larger than that of an elephant (Marino et al., 2007). It is unsurprising that encephilization (a measure of the size of the brain relative to the body) is commonly linked to cognitive abilities, with some cetaceans having the second highest encephilization quotient after humans (Manager, 2013). A hypothesis put forward by Jerison (1973) that the encephilization quotient is a biological indicator of intelligence, with high encephilization quotients …show more content…
In addition to this, cetaceans were already well above the needed body size to deal with oceanic cooling meaning it would be futile for odontocetes to respond to these decreasing temperatures with adjustment to brain or body size (Marino et al., 2007). Hence these changes are unlikely to be due to the changing oceanic temperature and it is likely other factors were the influence of this modification (Marino et al.,
Modern cetacean brains are among the largest of all mammals in terms of both general size and in relation to body size, with the largest brain in the animal kingdom being possessed by the sperm whale (Physeter macrocephalus) (Marino, 2004) with a mass of 60% larger than that of an elephant (Marino et al., 2007). It is unsurprising that encephilization (a measure of the size of the brain relative to the body) is commonly linked to cognitive abilities, with some cetaceans having the second highest encephilization quotient after humans (Manager, 2013). A hypothesis put forward by Jerison (1973) that the encephilization quotient is a biological indicator of intelligence, with high encephilization quotients …show more content…
In addition to this, cetaceans were already well above the needed body size to deal with oceanic cooling meaning it would be futile for odontocetes to respond to these decreasing temperatures with adjustment to brain or body size (Marino et al., 2007). Hence these changes are unlikely to be due to the changing oceanic temperature and it is likely other factors were the influence of this modification (Marino et al.,