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Treeshrews hold about 10% of their body mass in their brain. [16] Generally speaking, the larger the animal, the smaller the brain-to-body mass ratio is. Thus, large whales have very small brains compared to their weight, and small rodents like mice have a relatively large brain, giving a brain-to-body mass ratio similar to humans. [4]
Cephalopods have large, well-developed brains, [8] [9] [10] and their brain-to-body mass ratio is the largest among the invertebrates, falling between that of endothermic and ectothermic vertebrates. [11] The nervous system of cephalopods is the most complex of all invertebrates.
Mice have a direct brain/body size ratio similar to humans (1/40), while elephants have a comparatively small brain/body size (1/560), despite being quite intelligent animals. [18] Treeshrews have a brain/body mass ratio of (1/10). [19] Several reasons for this trend are possible, one of which is that neural cells have a relative constant size ...
An elephant's brain weighs just over 5 kg (11 lb), a bottlenose dolphin's 1.5 to 1.7 kg (3.3 to 3.7 lb), whereas a human brain is around 1.3 to 1.5 kg (2.9 to 3.3 lb). Brain size tends to vary according to body size. The relationship is not proportional, though: the brain-to-body mass ratio varies. The largest ratio found is in the shrew. [57]
Octopuses (along with cuttlefish) have the highest brain-to-body mass ratios of all invertebrates; [48] this is greater than that of many vertebrates. [49] Octopuses have the same jumping genes that are active in the human brain, implying an evolutionary convergence at molecular level. [50]
Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase the amount of brain mass available for more complex cognitive tasks. [2] Allometric analysis indicates that in general, mammalian brain size scales at approximately the 2 ⁄ 3 or 3 ⁄ 4 exponent of body mass. [ 3 ]
Their predators include dolphins, larger fish (including sharks), seals, seabirds, and other cuttlefish. The typical life expectancy of a cuttlefish is about 1–2 years. Studies are said to indicate cuttlefish to be among the most intelligent invertebrates. [2] Cuttlefish also have one of the largest brain-to-body size ratios of all ...
The nervous system of cephalopods is the most complex of the invertebrates [14] [15] and their brain-to-body-mass ratio falls between that of endothermic and ectothermic vertebrates. [ 12 ] : 14 Captive cephalopods have also been known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on captive ...