Carnivore Cortical Neuron Counts

[Recusant]

A neutral topic title to describe a recent study which indicates that dogs are generally more intelligent than cats. I don't think many people who've lived with both will be surprised by this, nor that raccoons, whose brains are about the same size as cats, have more cortical neurons than cats. Unlike some () I actually like cats, so I'm not posting this to promote an anti-feline agenda. 

"Dogs Have More Brain Neurons Than Cats, New Study Says" | SciNews

According to the first study to count the number of cortical neurons in the brains of a number of carnivores, dogs have about 530 million cortical neurons while cats have about 250 million neurons; for comparison, humans have 16 billion cortical neurons. The findings appear in the journal Frontiers in Neuroanatomy.

"In this study, we were interested in comparing different species of carnivorans to see how the numbers of neurons in their brains relate to the size of their brains, including a few favorite species including cats and dogs, lions and brown bears," said senior author Dr. Suzana Herculano-Houzel, of Vanderbilt University.

"I believe the absolute number of neurons an animal has, especially in the cerebral cortex, determines the richness of their internal mental state and their ability to predict what is about to happen in their environment based on past experience."

Dr. Herculano-Houzel and colleagues picked carnivorans to study because of their diversity and large range of brain sizes as well as the fact that they include both domesticated and wild species.

The researchers analyzed the brains of one or two specimens from each of eight carnivoran species: ferret, mongoose, raccoon, cat, dog, striped hyena, lion and brown bear.

"We expected that our measurements would confirm the intuitive hypothesis that the brains of carnivores should have more cortical neurons than the herbivores they prey upon," they explained.

"That is because hunting is more demanding, cognitively speaking, compared to the herbivore's primary strategy of finding safety in sheer numbers."

However, that proved not to be the case — the team determined that the ratio of neurons to brain size in small- and medium-sized carnivores was about the same as that of herbivores, suggesting that there is just as much evolutionary pressure on the herbivores to develop the brain power to escape from predators as there is on carnivores to catch them.

In fact, for the largest carnivorans the neuron-to-brain-size ratio is actually lower.

The authors found that the brain of a golden retriever has more cortical neurons than a striped hyena, African lion and even brown bear, even though the latter species have up to 3 times larger cortices than dogs.

The bear is an extreme example. Its brain is 10 times larger than a cat's, but has about the same number of neurons.

The scientists also found that raccoons have dog-like numbers of neurons in their cat-sized brain, which makes them comparable to primates in neuronal density.

[Continues . . .]

[Dave]

That is very jnteresting and, thinking about the behaviours - especially ptonlem solving ones - thst I have wstched friend's oets oeform it doonsvyo make sense.

Now, what about a neuron comparison between parrots, corvids, pigeons and chickens . . . And then between those and cats and dogs. Reckon the average crow has more brain power than the average cat!

[xSilverPhinx]

Yes, very interesting. Dr. Suzana Herculano-Houzel, one of the authors, is a Brazilian neuroscientist who is currently in the US because the Brazilian government is systematically cutting spending in the sciences. She's brilliant, but according to one of my former professors, not a very nice person. I don't know, I never met her.

Oh well.

As for the paper, I'd bet that social carnivore species in general are more intelligent than solitary ones, therefore it's no surprise to me that dogs are smarter than cats. Social interactions and being 'tuned' into another's state of mind requires a lot of brain power.

[Tank]

...
As for the paper, I'd bet that social carnivore species in general are more intelligent than solitary ones, therefore it's no surprise to me that dogs are smarter than cats. Social interactions and being 'tuned' into another's state of mind requires a lot of brain power.

Can't argue with this logic.

[Pasta Chick]

I had the same thought about social carnivores, but then I would expect a similar uptick among social herbivores (I didn't see that mentioned either way). It also doesn't explain raccoons scoring so high.

What also stood out to me is that taxonomy is not necessarily indicative of behavior. This study is using animals that taxonomically classified as carnivores, however many of the higher scoring animals are actually primarily scavengers with highly variable, often omnivorous diets in practice (dogs, raccoons)

[xSilverPhinx]

I had the same thought about social carnivores, but then I would expect a similar uptick among social herbivores (I didn't see that mentioned either way). It also doesn't explain raccoons scoring so high.

What also stood out to me is that taxonomy is not necessarily indicative of behavior. This study is using animals that taxonomically classified as carnivores, however many of the higher scoring animals are actually primarily scavengers with highly variable, often omnivorous diets in practice (dogs, raccoons)

Yeah I wasn't sure whether raccoons were considered social animals, apparently, according to a few studies cited in Wikipedia, they have some sort of social structure, considering there's a high enough number of raccoons per area.

Social behavior

Eastern raccoons (P. l. lotor) in a tree: The raccoon's social structure is grouped into what Ulf Hohmann calls a "three class society".

Studies in the 1990s by the ethologists Stanley D. Gehrt and Ulf Hohmann suggest that raccoons engage in gender-specific social behaviors and are not typically solitary, as was previously thought.[126][127] Related females often live in a so-called "fission-fusion society", that is, they share a common area and occasionally meet at feeding or resting grounds.[128][129] Unrelated males often form loose male social groups to maintain their position against foreign males during the mating season—or against other potential invaders.[130] Such a group does not usually consist of more than four individuals.[131][132] Since some males show aggressive behavior towards unrelated kits, mothers will isolate themselves from other raccoons until their kits are big enough to defend themselves.[133] With respect to these three different modes of life prevalent among raccoons, Hohmann called their social structure a "three class society".[134] Samuel I. Zeveloff, professor of zoology at Weber State University and author of the book Raccoons: A Natural History, is more cautious in his interpretation and concludes at least the females are solitary most of the time and, according to Erik K. Fritzell's study in North Dakota in 1978, males in areas with low population densities are solitary as well.[135]

I would like to see a comparison made between social and non-social herbivores in terms of proportional neuron count, but I don't think either would score as high as carnivores (or even omnivores) because the bioavailability of energy is much lower in plants, meaning an animal would have to eat way more vegetable mass just extract x calories while a meat-eater would each much less for the same number of calories.  And the brain uses up a lot of energy, with more cognitively flexible brains using more than the "simpler" ones.

What intrigues me is that even though body mass is a limiting factor because of the metabolic cost of having a more complex brain, and most dogs are larger than most domesticated cats, why do dogs have more cortical neurons? Shouldn't it be the other way round?

Maybe, evolutionary pressures selected for animals that could hunt in groups, as this ups the chances of success compared to the solitary hunter. More food means more energy for a more energy-demanding brain. Opportunistic scavenging also ups the odds of eating a meal, though once again, animals who scavenge in groups are better able to defend their meal against other scavengers.     

I would also like to see social felines such as lions compared to solitary ones such as leopards. They live in the same habitats, eat mostly the same food, but have different social behaviours.