List of animals by number of neurons

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Brief comparisons of number of whole brain neurons (top) and cerebral cortex neurons (bottom) among five mammals.

This is a list of representative animals by the number of neurons in their whole nervous system and the number of neurons in their brain (for those with a brain). These numbers are estimates derived by multiplying the density of neurons in a particular animal by the average volume of the animal's brain.

The whole human brain contains 86 billion neurons and either 19 or 23 (respectively female and male) billion neurons in the cerebral cortex.


Neurons are the cells that transmit information in an animal's nervous system so that it can sense stimuli from its environment and behave accordingly. Not all animals have neurons; Trichoplax and sponges lack nerve cells altogether.

Neurons may be packed to form structures such as the brain of vertebrates or the neural ganglions of insects.

The number of neurons and their relative abundance in different parts of the brain is a determinant of neural function and, consequently, of behavior.

Whole nervous system[edit]

All numbers for neurons but Caenorhabditis and all numbers for synapses are estimations.

Name Neurons in the brain/whole nervous system Synapses Details Image Source
Sponge 0
Trichoplax 0
Trichoplax mic.jpg
Caenorhabditis elegans (roundworm) 302 ~7,500
Adult Caenorhabditis elegans.jpg
Jellyfish 5,600 Hydra vulgaris (H. attenuate)
Jelly cc11.jpg
Box jellyfish 8,700–17,500 adult Tripedalia cystophora (8 mm diameter) – does not include 1000 neurons in each of the four rhopalia
Medicinal leech 10,000
Svømmende blodigle.JPG
Pond snail 11,000
Common snail.jpg
Sea slug 18,000
Aplysia californica.jpg
Amphioxus 20,000 central nervous system only Branchiostoma lanceolatum.jpg [9]


Fruit fly 250,000 < 1×10^7
Drosophila melanogaster - side (aka).jpg


Larval zebrafish 100,000 Zebrafish embryos.png [13]
Lobster 100,000
Lobster 04.jpg
Ant 250,000 Varies per species
Ant head closeup.jpg


Honey bee 960,000 ~1×10^9
Bees Collecting Pollen 2004-08-14.jpg
Cockroach 1,000,000
Adult zebrafish ~10,000,000 cells (neurons + other) Zebrafisch.jpg [19]
Frog 16,000,000
Magnificent tree frog (Litoria splendida) crop.jpg
Smoky shrew 36,000,000 SmokyShrew23.jpg [21]
Short-tailed shrew 52,000,000 Blarina carolinensisPCSL20933B.jpg [21]
House mouse 71,000,000 ~1×10^12 House mouse.jpg [22]
Golden hamster 90,000,000 Peach the pet hamster.jpg [22]
Star-nosed mole 131,000,000 Condylura.jpg [21]
Zebra finch 131,000,000 Brain only Taeniopygia guttata -Karratha, Pilbara, Western Australia, Australia -male-8 (2).jpg [23]
Brown rat 200,000,000 ~4.48×10^11 Rattus norvegicus 1.jpg [24]
Eastern mole 204,000,000 ScalopusAquaticus.jpg [21]
Guinea pig 240,000,000 Two adult Guinea Pigs (Cavia porcellus).jpg [22]
Common treeshrew 261,000,000 Stavenn Tupaia glis 00.jpg [25]
Pigeon 310,000,000 Brain only Paloma bravía (Columba livia), Palacio de Nymphenburg, Múnich, Alemania01.JPG [23]
Octopus 500,000,000
Common marmoset 636,000,000 Marmoset copy.jpg [25]
Cat 760,000,000 ~1×10^13
Cat mouth closed.jpg
Black-rumped agouti 857,000,000 Dasyprocta punctata (Mexico).jpg [22]
Northern greater galago 936,000,000 Garnett's Galago (Greater Bushbaby).jpg [25]
Three-striped night monkey 1,468,000,000 Stavenn Aotus trivirgatus 00.jpg [25]
Capybara 1,600,000,000 Capybara male.jpg [22]
Raven 2,171,000,000 Brain only Raven (Corvus corax) (8).jpg [23]
Common squirrel monkey 3,246,000,000 Common.squirrel.monkey.arp.jpg [25]
Tufted capuchin 3,691,000,000 Sapajus apella apella (French Guyana) 4.jpg [25]
Rhesus macaque 6,376,000,000 Macaca mulatta in Guiyang.jpg [25]
Orangutan 32,600,000,000
Orang Utan, Semenggok Forest Reserve, Sarawak, Borneo, Malaysia.JPG
Gorilla 33,400,000,000
Male gorilla in SF zoo.jpg
Human 86,000,000,000 ~1.5×10^14 Synapses for average adult
Akha cropped hires.JPG
African elephant 257,000,000,000
African Bush Elephant.jpg

Cerebral cortex[edit]

Only mammals appear in this list, because only mammals have a cerebral cortex (although the pallium of reptiles and birds is also frequently referred to as "cortex".)

Name Neurons in the cerebral cortex Details Image Source
Mouse 4,000,000 Genus Mus, musculus
Rat 18,000,000 Genus Rattus, unknown species
Rat diabetic.jpg


Hedgehog 24,000,000 Subfamily Erinaceinae, unknown genus and species
Opossum 27,000,000 Family Didelphidae, unknown genus and species
Opossum 2.jpg
Dog 160,000,000 Canis lupus familiaris
YellowLabradorLooking new.jpg
Cat 300,000,000 Felis catus or Felis silvestris catus
Cat mouth closed.jpg
Tarsius 310,000,000 Genus Tarsius, unknown species
Tarsius tarsier Tandurusa zoo.JPG
Squirrel monkey 430,000,000 Genus Saimiri, unknown species
Saimiri sciureus-1 Luc Viatour.jpg
Domesticated pig 425,000,000 Sus scrofa
Sow with piglet.jpg
Raccoon 453,000,000 Raccoon (4152678243).jpg [39]
Rhesus macaque 480,000,000 Macaca mulatta
Macaca mulatta in Guiyang.jpg
Gracile capuchin monkey 650,000,000 Genus Cebus, unknown species
Capuchin Costa Rica.jpg
Horse 1,200,000,000 Equus ferus caballus
Nokota Horses cropped.jpg
Guenon 2,500,000,000 Genus Cercopithecus, unknown species
African elephant 5,600,000,000 Genus Loxodonta, unknown species
Elephant in Botswana.JPG
Chimpanzee 6,200,000,000 Genus Pan, unknown species
Lightmatter chimp.jpg
Orangutan 8,900,000,000
Orang Utan, Semenggok Forest Reserve, Sarawak, Borneo, Malaysia.JPG
Gorilla 9,100,000,000
Male gorilla in SF zoo.jpg
False killer whale 10,500,000,000 Pseudorca crassidens
False killer whale 890002.jpg
Fin whale 15,000,000,000 Balaenoptera physalus
LMazzuca Fin Whale.jpg
Human 21,000,000,000 For average adult
"The average number of neocortical neurons was 19 billion in female brains and 23 billion in male brains."
Akha cropped hires.JPG
Long-finned pilot whale 37,200,000,000 Globicephala melas: "For the first time, we show that a species of dolphin has more neocortical neurons than any mammal studied to date including humans."
Pilot whale spyhop.jpg

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