Evolution Mind

Birds must choose between big brains and big guts

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How important are big brains to survival? From ScienceDaily:

Because the brain is such a costly organ to develop and maintain, biologists have long been interested in understanding how large brain size — in all species — could have evolved …

Previous studies had found general trends towards larger relative brain sizes in higher latitudes, where conditions are more variable — consistent with the cognitive buffer hypothesis. Fristoe and Botero’s new study is different because it looks at the full distribution of brain sizes across environments, allowing them to test whether different sizes are over- or under-represented.

Excluding contributions from migrants — the birds that live in polar or temperate environments only during more favorable times of the year — the researchers found that at high latitudes, bird brain size appears to be bimodal. This morphological pattern means that bird brains are significantly more likely to be relatively large, or relatively small, compared to body size.

What was going on here? Fristoe, born in Alaska, had a few ideas.

In fact, Fristoe suggests that the Alaska state bird, the ptarmigan, might be a good poster child for the small-brained species. Endearing though she is — with her plushy bosom, feathered feet and unusual chuckling call — she’s not exactly known for her smarts. The ptarmigan can, however, chow down on twigs and willow leaves with the best of them.

“In our paper, we find that small-brained species in these environments employ strategies that are unachievable with a large brain,” Fristoe said. “First, these species are able to persist by foraging on readily available but difficult to digest resources such as dormant plant buds, the needles of conifers, or even twigs.

“These foods can be found even during harsh winter conditions, but they are fibrous and require a large gut to digest,” he said. “Gut tissue, like brain tissue, is energetically demanding, and limited budgets mean that it is challenging to maintain a lot of both.

“We also found that these species have high reproductive rates, producing many offspring every year,” Fristoe said. “This would allow their populations to recover from high mortality during particularly challenging conditions. Because big-brained species tend to invest more time in raising fewer offspring, this is a strategy that is not available to them.” …

“Given that our own species uses its brain to cope with these changes, it is not really surprising that biologists, ourselves included, have historically exhibited a bias toward thinking about environmental variability as a force that drives the expansion of brain size,” Botero said. “But the interesting thing that we find here is that when we take a broader view, we realize that other strategies also work — and remarkably, the alternative here involves making a brain actually smaller!” Paper. (open access) – Trevor S. Fristoe, Carlos A. Botero. Alternative ecological strategies lead to avian brain size bimodality in variable habitats. Nature Communications, 2019; 10 (1) DOI: 10.1038/s41467-019-11757-x More.

This is further indirect evidence— not, of course, drawn out here—that the human brain did not develop the way it did simply to enable survival.

See also: Do big brains matter to human intelligence?

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5 Replies to “Birds must choose between big brains and big guts

  1. 1
    Bob O'H says:

    This is further indirect evidence— not, of course, drawn out here—that the human brain did not develop the way it did simply to enable survival.

    Earth to News: humans are not birds. We also didn’t evolve at high latitudes.

  2. 2
    ET says:

    Earth to Bob O’H- There isn’t any evidence that humans evolved from non-humans. There isn’t even a way to scientifically test the premise. Biologists don’t even if brains could evolve…

  3. 3
    vmahuna says:

    So I’m guessing this COMPLETELY ignores carnivorous birds. And it would also seem to ignore migrating birds. So that leaves only “birds who were designed to live in places no one in their right minds want to live.” I.e., the, how you say, “bird brained” birds.
    Is the same (or converse) true of desert birds? Do vegetarian desert birds (if there are such things) also have either big intestines or big (a VERY relative term in birds) brains?
    Birds were designed: 1) to look cute to the humans whose design would be finished in a couple more million years, 2) to pollinate the few plants for which the Insect Design Group hadn’t already designed an insect pollinator.
    So does the gut/brain controversy have ANYTHING to do with the price of tea in China?

  4. 4
    vmahuna says:

    Ya know, if you COMPLETELY confuse the QUESTION, ya get weird (and worthless) answers.
    The “small brained birds” are vegetarians (e.g., CHICKENS) and the “big brained birds” are carnivores (e.g., EAGLES). So the Chickens only need a brain big enough to process “scratch dirt, eat seeds”. Whilst the Eagles need a brain big enough to: FLY, identify prey against various backgrounds, strike and kill suitable prey, navigate back to the nest, defend themselves from other carnivorous birds, eat the dumb chickens for Sunday dinner.
    But I guess it would have been harder to get the study published if they’d let some kids in high school (who would have got the QUESTION right) write it up.

  5. 5
    Bob O'H says:

    Vmahuna –

    So I’m guessing this COMPLETELY ignores carnivorous birds. And it would also seem to ignore migrating birds.

    No it doesn’t: there are carnivores in the data (you can get it as a CSV file), and they explicitly look at the amount of plant food in the diet. It also doesn’t ignore migratory species: they were looked at, but there was no pattern.

    You can read the full paper, as it’s open access.

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