Amazing Animal Brains: 13 Fascinating Neurological Facts


The brain is a fascinating and mysterious organ, a little biological computer that dictates everything its owner does. Animal brains vary between small clusters of neurons to the enormous and astonishingly complex brains of our own species. These 13 animals may just have the most strange and interesting brains in all the world, from spiders with brains that spill into their legs to sea squirts that digest their own brains as they grow.

Spider Brains that Spill Into Their Legs


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Spiders’ brains are so large relative to the rest of their bodies, they spill out of their heads – and all the way down into their legs. The Smithsonian Tropical Research Institute made this discovery , finding that the central nervous systems of the world’s smallest spiders fill up almost 80 percent of their total body cavity.

“We suspected that the spiderlings might be mostly brain because there is a general rule for all animals, called Haller’s rule, that says that as body size goes down, the proportion of the body taken up by the brain increases. Human brains only represent about 2-3% of our body mass. Some of the tiniest ant brains that we’ve measured represent about 15% of their biomass, and some of these spiders are much smaller.”

Leeches with 32 Brains


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To us, leeches are both horrifying and miraculous, latching on and sucking our blood in what can be an unwanted parasitic relationship or a helpful one that cleans up infected wounds. But there’s no denying that these creatures are absolutely fascinating – they have five pairs of eyes, 300 teeth and 32 brains. Well, technically, they only have one, but that brain is made up of 32 ganglia, which means the same thing in practice.

Giant Squid Eats Through its Brain


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Giant squid have to bite their food into relatively small pieces, because once they swallow, that food must fit through its donut-shaped brain as it goes down the esophagus. For such a large creature (which happens to possess the largest eyes of any known living creature on earth), the giant squid’s brain is surprisingly small.

“The male giant squid has to use a puny 15g brain to coordinate 150kg of weight, 10m of length and a 1.5m-long penis,” Steve O’Shea of the Auckland University of Technology told the UK’s Metro.

Zombie Ants with Fungus on the Brain


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It’s not the ant’s brain that is special in this case, but rather how it reacts to a certain species of parasitic fungus. The Cordyceps fungus infects insects and turns them into zombies, manipulating their behavior in order to disperse their spores and multiply. Like something out of a nightmare, Cordyceps feeds on the ant’s non-vital organs as its filaments grow into the ant’s brain, causing the ants to climb nearby plants and climb to the top. Once they do so, the fungus kills the ant and sprouts from its head in the form of a mushroom.

Tiny Wasps with the Smallest Nervous Systems


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Despite having bodies complete with eyes, brains, wings, muscles, guts and genitals, the teeny tiny Megaphragma mymaripenne wasp is smaller than a single-celled amoeba. Researchers found that this wasp has one of the smallest nervous systems of any insect. What few neurons exist inside the wasp’s head when it’s a juvenile actually burst apart when it becomes an adult, because there’s not enough room in its head. Good thing they only live for five days.

Nematode’s Tiny but Powerful Brain


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The minuscule brain of the C. elegans nematode worm has just 302 neurons, but in spite of this, it’s able to carry out the same functions as the nervous systems of higher organisms. Scientists are studying this amazing nematode brain to understand the basic mechanisms that facilitate complex behaviors. In fact, these behaviors may just help them unlock secrets of the human brain.

Sea Squirts that Eat Their Own Brains


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Sac-like creatures that latch onto coral and filter their food from sea water, sea squirts are hermaphroditic, producing tadpole-like larvae that disperse to find new homes on which to grow. At this larval stage, sea squirts have the same anatomical characteristics as fish, birds, reptiles and mammals, but as they grow, they lose their minds – literally. They digest their own cerebral ganglia, which controls movement, because once they’re sedentary, they no longer need it.

Fish with Gender-Unequal Brains


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The old misogynist belief that women aren’t as smart as men was proven wrong a long time ago, but in one tiny subspecies in a very particular area of the world, this belief is actually correct. Three-spined stickleback fish living in Lake Myvatn in Iceland have a distinct disparity between the brain sizes of males and females. Researchers have speculated that this might be due to the fact that the males have the more challenging role, building nests, performing courtship dances and caring for the eggs, while the females must only choose a mate and lay the eggs.

Woodpeckers with Air Pockets in their Skulls


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How is it that woodpeckers don’t get brain damage from banging their beaks on hard surfaces all day long? Like all birds, woodpeckers have very complex skulls full of tiny, very lightweight bones; the skull of an average bird weighs just 1% of the bird’s body weight. The woodpecker has a built-in protective mechanism that cushions the brain from the jolts of its activities: air pockets.

Cavalier King Charles Spaniel’s Smushed Brain


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Prized for their adorable looks and friendly personalities, Cavalier King Charles Spaniels are growing more popular as pets in the United States. But all the breeding that has occurred over centuries to produce this particular look has led to a very serious problem: a condition called syringomyelia, in which the animals’ brains are too big for their skulls. Veterinary Neurologist Dr. Claire Rusbridge described this dog’s brain as a “size 10 foot that’s been shoved into a size 6 shoe.” The condition affects up to 1/3 of the total population of the breed, and it’s extremely painful for the poor dogs.

Corvids Are Impressively Smart


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Corvids, the group of birds that includes crows, ravens, rooks, jackdaws, jays and magpies, are much smarter than most people realize – possibly as smart as primates. Their extraordinary memories, social reasoning skills and ability to craft and use tools has astonished scientists.  Their use of tools, including honing sticks into hooks to access grubs, may surpass that of primates like chimpanzees. Says the aptly named scientist Christopher Bird, “”If they are being watched, they will hide their food, but they will do some ‘fake hides’ as well – so they’ll put their beak in the ground, but not place the food. It’s a bit like a confusion strategy.”

Dolphins: Brains Bigger Than Ours


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Did you know that dolphins’ brains are actually larger than ours? While creatures like corvids show that size isn’t always important, cetaceans like bottlenose dolphins have the ability to recognize, remember and solve problems, making them officially the closest in intelligence to humans among all creatures in the animal kingdom. The neocortex of the dolphin is more complex than our own, structured to allow for self-awareness. This self-awareness came under scrutiny after the death of a trainer at SeaWorld, who was killed by the largest member of the dauphin family, a killer whale.

Says Emory University dolphin expert Lori Marino, “I’m not trying to second-guess what was in this particular whale’s mind. But, certainly, if we are talking about whether killer whales have the wherewithal and the cognitive capacity to intentionally strike out at someone, or to be angry, or to really know what they are doing, I would have to say the answer is yes.”

The Human Brain


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Of course, humans are animals, too, and not to toot our own horn, but our brains are pretty spectacular. It’s clear that our brains are more highly evolved than those of any other species, but the complexity of them is sometimes beyond our own comprehension. They use 20% of the total oxygen in our bodies, can process information at the equivalent of 268 miles per hour, and can live for up to six minutes without oxygen. The saying that we only use 10% of our brains, however, is not true; every part of the brain has a known function.