Somewhere I read that the brains of fruit eating bats are twice as large as the brains of insect eating bats. I realize I may be begging the question here by assuming that the author who wrote about the bigger brains of fruit eating bats had evidence to back up the claim. I have not been able to substantiate that claim. So here are the questions----#1 Are the brains of fruit eating bats twice as large as those of insect eating bats and #2 If so, why?
Yes. Megachiropterans (fruit bats) are much larger, with wingspans generally around 24 inches - and crania to match. Insectivorous bats (microchiropterans)rarely exceed a foot in wingspan (although some of the larger “micro-bats” also eat nectar, fish, etc…) Probably the increased brain size has to do with the need to process sensory information, as fruit bats are dependent on smell & sight as well as sound, but I’d have to check my textbook. (see texts by Kunz for the biology, and British Museum/Anderson for morphology.
Although true, what’s the point? Sounds like Vegan propaganda to me. Am I to conclude from this fact that Vegetarians have bigger brains ( and thus are smarter) than us meat-eating barbarians?
The point is to learn if it is true, and if so, why it is true. Your conclusion is yours alone. I do not share it.
I’d say it probably has to do with energy requirements. Fruit is a high energy food that doesn’t need much work in the way of stalking, thus a little more energy can be wasted on body size. Insects on the otherhand, are small, often agile, and thus need a smaller faster predator, so those bats are generally smaller and faster than the larger fruit eaters. A similar case can be made with birds I believe. Insect eating birds are generally smaller than the birds that eat larger prey…they need to be, hard to turn on a dime when you are the size of a semi’s tire. 
I don’t think the sensory arguement holds really, since Hummingbirds are incredibly small, yet subsist entirely on nectar found by scent and sight.
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I apologize, DSC. I mistook your post for something it wasn’t.
Cranial/brain/body size is not a function of whether energy can be “wasted” as opposed to another metabolic need, such as chasing prey, last I looked, and studied evolutionary biology. (Otherwise slugs would speak French, and couch potatoes would be geniuses. Anyone else chime in ?) Forget the hummingbirds, and compare apples with apples, or in this case bats with bats.
Fruit bats have to roam far for food, are more likely to have predators attack, and though they have weak sonar (if any, depends on species), they do have great hearing and highly developed eyesight and smell. The processing capacity (excuse computer analogy) for the latter two particularly require more brainpower, oxygen, etc… and that accounts for the increased cranial size.
And no, this is not some kind of pro-Vegan argument.
PapaBear, check Marvin Harris’ comparative studies of meat-eating hunter-gatherer societies and [primarily] agricultural societies. Briefly, your Kalakari Bushman has to spend 4-6 hours a day to provide for subsistence, freeing up the rest of the time for tradition, crafts, play, family, etc… and your Javanese rice farmer works 17 hours a day, with little time for much else. Who has more leisure time to ponder the world around them ? (without modem access)
Way to jump to conclusions. Feeling threatened? I found the question very interesting, as my own intuition would have thought that more brains would be required to hunt insects than to sit around munching fruit. (I realize you apologized for the comment, but I still find it incredibly out of the blue that you made it in the first place)
>^,^<
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WOO HOO! I finally get to come into a thread behind PapaBear without having to begin my post with “Papa is right about…”! Thanks for the bone, Papa!
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Anytime, Doc! I hope everyone made note of my apology 2 posts down from my little snit-fit. I wasn’t looking for a fight, honest. I’m having a hard time seeing the forest for the trolls lately.
Anytime, Doc! I hope everyone made note of my apology 2 posts down from my little snit-fit. I wasn’t looking for a fight, honest. I’m having a hard time seeing the forest for the trolls lately.