Why do whales need such big brains?

Actually, they may need such a large brain - because they are fairly intelligent. Maybe even more so than humans, just in a different way. They have some senses we humans don't - like echolocation. They can do things with sound that we can't, and there seems to be indications that they have emotions and do quite a bit of thinking.

http://www.onegreenplanet.org/animalsandnature/hum...

Good article that talks about this all. We tend to think that all cetaceans do is swim around and eat fish, maybe jump out of the water once in a while, but the reality is they live quite a full, rich life. And thus need a pretty big brain to manage all that. Especially since they don't have the ability to write things down or look them up on the internet.

They don't 'need' them, being an advanced and highly intelligent animal, they simply have them.

I was just watching a humpback whale expressing pure joy and happiness, very obvious and emotions only found in much more intelligent animals.

Watch for yourself and try to tell me this behavior near the end isn't that of sheer joy:

https://www.youtube.com/watch?v=tcXU7G6zhjU

my theory is, whale brains enlarge when they are removed from the body or when out of the water. we need to actually have people outside of a deep submarine to cut open a whale brain and they will see it is actually small

Scientists have found that as an animal gets bigger, its brain increases in size. However, they also found that the brain increases in size much more slowly than the body. Therefore they came up with a measure known as EQ (Encephalization Quotient), which measures how big an animals brain is vs. how big it is expected to be for an animal its size. Cats and dogs both have an EQ of sllightly above 1. That means they are about equal in intelligence and also slightly more intelligent than other animals their size. In contrast, humans have an EQ of raound 7, meaning our brain is about 7 times as large as an animal our size. In comparison, dolphins have an EQ of around 5, giving them the highest EQ besides humans, higher than even the great apes.

If we look at our closest relatives, we see a negative correlation between EQ and availability of food. Humans evolved in the African savanna, which has the least amount of edible food for an ape or human since the most abundant vegetation is grass, which cannot be digested by humans or apes.. Human ancestors at first only had the same sized brain as a chimpanzee brain, but starting around 2 million years ago, we had a drastic increase in brain size when Homo erectus evolved. Homo sapiens also has a much larger brain than Homo erectus, when we evolved about 150,000-200,000 years ago in Africa from Homo erectus. The gorilla, which lives in the same area as chimps, has a smaller brain than the chimp, because they are able to occupy the richest habitats by excluding the smaller chimps from the same area. Gorillas spend less time each day looking for food than the chimp. The chimp not only spends more time looking for food, but they have to come up with new kinds of food, such as termites and they also hunt monkeys and other small primates for food to supplement their diet. They need a bigger brain to find enough food.

In comparison, the bonobo, which evolved from the chimp and which is found across the Congo River from areas inhabited by chimps and gorillas, has a smaller brain than the chimp but a larger brain than a gorilla. Because neither the gorilla nor the chimp can swim, the bonobo is able to live in the best habitats within its small range, and they can find enough food without looking. They don't need to hunt monkeys for food. They have so much spare time that they spend a lot of it every day having sex. The bonobos brain either shrank or it stopped increasing in size after it last shared an ancestor with the chimp. We see a similar correlation in the capuchin, a New World monkey fround in the Western Hemisphere. The capuchin lives in a variety of habitats and it has to use its brain to find food in much of the area it occupies. The capuchin has the highest EQ among all New World monkeys, and they have higher EQ in fact than chimps.

Therefore the most likely explanation for the intelligence of whales and dolphins is that they needed it to find food in the ocean. Indeed, whales often use many different ingenious methods to find food, such as using bubble nets to trap fish, and the killer whale, which has a very big brain, may chase fish onto a beach before catching them on dry land, a new method of hunting invented by their big brain. The sperm whale, even though it has the largest brain of any animal alive, actually have a lower EQ than dolphins and killer whales. Nevertheless, it needs a bigger brain and higher EQ than blue whales and other baleen whales because it hunts an elusive prey, the giant squid. Baleen whales, OTOH, are filter feeders. Their food is abundant and they don't need a high EQ to find enough food. Brains cost a lot of energy to maintain. Our brain weighs less than 3 pounds, or about 1/50 of our total body weight or less, and yet it consumes 20% of our daily energy intake. Therefore, unless an animal needs a big brain to find food, they are better off having a smaller brain that needs less energy to maintain. Humans can starve to death a lot earlier than cats and dogs during times of food shortage because of our big brain. OTOH, we would starve to death even earlier if we don't have a brain that allows us to find food in places that do not have much food.

I would suspect that there's a lot of brain devoted to coordinating a huge number of muscle cells, and the rest of the brain is big because it came along for the ride, so to speak.