Wednesday, December 14, 2022

SearchResearch Challenge (12/14/22): Does animal color and weight change by latitude?

Colorful tropical birds... 

Keel-billed Toucan in Belize, Arctic tern in Alaska.  
P/C William Walker © 2016, 2010 see:

... are one of the glories of the avian world.  And I've noticed something odd--don't tropical birds seem much more colorful than the birds that live closer to the poles? 

When I think of jungle birds, brilliant parrots, toucans, and lorikeets come to mind.  Meanwhile, birds of the north such as Canada geese, finches, terns, and seagulls tend to be more muted.  Is this a real thing, or am I seeing something where nothing is going on?  Sure, there are brilliant red cardinals in the northern parts of the US, but on the whole... 

Similarly, isn't there a tendency for animals to be different sizes if they're in the north vs. equatorial places?  Seems to me that some animals (such as deer or foxes) seem to be bigger "up north" (say, Canada) than "down south" (say, Mexico).  There's a lot of variability, of course, but is there a general trend? 

Or am I just imagining things?  

Pondering this made me want to frame it as a Challenge for you.  Here you go... 

1.  Is it true that birds have more brilliant colors near the equator, and are less colorful as you go farther north?  If so, why would that be?  

2.  Is it true that the closer an animal species is to the poles, the larger they are?  Again, if so, why?  

The REAL question for us is how would you find out such a thing?  Remember that you'll want to not just search for positive examples of these observations, but also counter-examples.  (In truth, you'll probably want to find people who can speak with authority about such things.  Looking at one or two birds (or even a few dozen animals) over different latitudes probably won't tell you what's really going on.  

So.. how can you figure this out?  (Remember that I can be devious: one of these propositions might not be true!)  

Let us know what you discover, and HOW you found out? 

Search on!  


  1. First, sorry about being away for a while: I've been a bit busy.

    Second, I'll take a stab at the second question: "Is it true that the closer an animal species is to the poles, the larger they are? Again, if so, why?"

    In answer (without even doing any searching), I'd say no, it's not: When I was in Tanzania (East Africa, near the equator) as a Peace Corps Volunteer, I saw elephants, giraffes, and hippos while visiting a couple of its national parks. In fact, one day in 2008, when I was taking a bus through Mikumi National Park (west of Morogoro), I saw a herd of 20-30 elephants.

    As well, I know there are lions in Serengeti National Park.

    I also remember hearing that there were rhinos and Cape buffalo there (the former in the Selous Game Reserve). I confirmed this by looking it up at Wikipedia ( [another name for Cape buffalo] and

    A visit to Wikipedia also confirmed for me that there were elephants in India and Southeast Asia (, plus one of the earlier results I found showed that there were still rhinos in those parts of Asia. And, tigers can be found in India and Southeast Asia (though Siberian tigers are native to the Russian Far East and adjoining parts of Manchuria [China] and North Korea).

    So, given that there are a lot of big animals found in the tropics and near the equator, I'd say the answer to your question is "no."

    A few other notes (of interest):
    * I saw hippos while visiting Mikumi National Park, and, thankfully, they were submerged. They're kind of scary: They are as big as small cars and can run as fast as them, plus they have a bad temper. I also remember reading somewhere that, in the past, it was said in Tanzania that those who went to hunt hippos were not going to come back.
    * If you see a giraffe, it will stand absolutely still and stare at you. Then, if you turn your head, it will walk away.
    * If you're on a walking tour in a Tanzanian national park (as was the case with me, when I visited Arusha National Park while there), your ranger carries a rifle as protection against animals.

    1. I read question two differently. There are large animals near the equator and small (even microscopic) ones near the poles. I took it to be more comparative. For example, the largest blue whales are the Antarctic blue whales; ones found farther from the pole are smaller. I think the same is true of penguins.

    2. @Grace: That's an interesting way of looking at this question. So, I investigated that, first by seeing which species (aside from humans) had wide enough geographic ranges for this to matter. Reading indicated that some with ranges that cover significant parts of the Earth's surface are said to have a cosmopolitan distribution. Wikipedia ( listed several, such as houseflies, killer whales, blue whales, great white sharks, humans, dogs, cats, honey bees, and a type of wasp. And, I'm sure there are others.

      Species I looked at:
      * Blue whales (the example you listed): The largest subspecies is the Antarctic blue whale (, which live close to Antarctica during the summer, though most migrate north during the winter (
      * Dogs: The domesticated ones don't count, since humans are responsible for their size. I looked up their relatives in the family canidae (which includes wolves, foxes, and coyotes). Doing a search ("Canidae largest species") shows on the SERP that wolves are the longest. Another search (Canidae largest species by weight) states that gray wolves are the biggest by weight, though their range (according to Wikipedia) has included Eurasia and North America, including (historically) places like Mexico, India, and the southern Arabian peninsula ( Looking up gray wolf subspecies elsewhere on Wikipedia ( indicated the northwestern gray wolf was the biggest, and was in Alaska, Canada, and the northwestern United States. It also indicated that the Eurasian wolf was the biggest in the Old World, with the Scandinavian and Russian ones being bigger than ones in Western Europe (
      * Great white shark: There is only one subspecies, according to the Google SERP. And, according to Live Science (, they live in temperate and tropical oceans, and migrate.
      * Honey bee: I searched for largest species of honey bee, and found the Himalayan giant honey bee (, which can be over 3 cm (1.2") long, and which is found in the Himalayas stretching from Nepal to Southeast Asia. Looking at the Wikipedia entry for honey bees ( showed that they can be found worldwide.
      * Cats: I did a search for the largest ones. Live Science ( listed and explained the nine largest, with the biggest being tigers. I then searched for the largest subspecies of tiger; the Google SERP indicated that Siberian tigers are the biggest, plus the source was the Smithsonian Institute.

      Conclusion: In species that are widely distributed, at least some subspecies with the largest members are located closer to the poles than the equator.

    3. You have really researched this. I realize that I do not have enough of a background in biology to be able to think rigorously about genus, species, subspecies, etc. Also, does the question mean that “the closer an animal species is to the poles, the larger they are” in comparison to other (similar?) species or to other members of their own species? It does seem that in general, “like” animals are larger closer to the poles. However, human activity such as hunting and habitat loss can influence where certain animals are still found or have disappeared.

      In the case of penguins, the largest ones are in Antarctica and the smallest are found in the Galapagos and Australia/New Zealand.

    4. This is a correct reading... it's not that individuals near the equator are large or small, but that for a given species, the trend is that as that you look at that species from equator to pole, the trend is that they are (on average) larger in size. Similar story for coloration in birds: the trend is for birds to be more colorful (in general) as you approach the equator.

  2. 1.
    [are the most colorful birds from equatorial countries]

    Computer analysis has shown that 19th-century naturalists including Charles Darwin were right: birds near the equator are more colourful. Article follows.

    Journal reference: Nature Ecology & Evolution, DOI: 10.1038/s41559-022-01714-1

  3. 2. Polar size.
    My hunch is that large elephants do not live near the Poles. Nor elephants of any size. Ditto lack of hippopotarmys near Inuvik. or The Amundsen–Scott South Pole Station.

  4. was lost, but wandered north to the 45th parallel (45 Degrees North Latitude)…
    near Egg Harbor, Wisconsin… strange, colorful, mutant avian things happen there…
    might not be definitive proof of anything.
    rare birds
    half way to the North Pole

  5. Hello everyone

    Still working on the the challenges, but came across something interesting that I'd never encountered regarding a paywall for research papers.
    Initial search was [why are birds more colorful in the tropics]. Skimming the Search Engine Results Page (SERP) gave the impression that a study was published earlier this year appears to support a hypothesis of Darwin and others that birds are more colorful in the tropics. I went to link to a Popular Science article
    Songbirds near the equator really are hotter, color-wise
    My thought was that they would have a citation to the study I had seen in the SERP. And they did "the team reported on April 4 in the journal Nature Ecology & Evolution."
    Here is the interesting thing, clicking on the link took me to a page to the study with a paywall, but before I could copy the title to search for a freely available version, I was forwarded to the article with a small banner that says,
    SharedIt - Online access to this article has been provided by Springer Nature SharedIt.

    Fascinated by this, I clicked on "What's This" in the banner to SharedIt
    Springer Nature’s commitment to content sharing

    This was cool as I always get a bit disheartened when searching and then hitting a paywall and feel a bit underhanded by trying to find it available free elsewhere.

    Back to the challenges.

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  7. …after the flashy - or drab - bird has departed —— seems consistent regardless of location…
    Word of the Day: Urohidrosis (a good reason to stay in the colder areas… and to moisturize your legs)
    have been told I have bird legs…
    can't argue with Charles about some things…
    "Darwin called vultures “disgusting” with bald heads “formed to wallow in putridity”."
    but they are colorful
    "The uppermost layer of the youngest deposit of Guano has a white or whitish-gray color, which becomes grayish yellowish brown with increasing thickness. It used to deliver the much appreciated white Guano (Huano blanco). The top layers are similar to fresh clay, of a tough, soft consistency."
    Huano blanco - lacks hue
    — the big blanco creatures - & walruses/sea lions, don't even go there, oh boy!
    bigger, becoming smaller

    1. Thanks, remmij, I needed Urohidrosis in my vocabulary.

    2. 😊 😃 ツ
      Dan - is your vocab really that extensive or were you being prim & sarcastic ;-/
      "Like most bird groups, vultures can be referred to as a flock, though they can also be labelled as either a venue, volt, or a committee. However, when it comes to the vulture group feeding around a carcass, they are called a wake, and when the birds are in flight formation, they are known as a kettle."
      by activity
      different birds
      ( ͡° ͜ʖ ͡°) ¬‿¬
      "We saw her duck is a paraphrase of We saw her lower her head and of We saw the duck belonging to her, and these last two sentences are not paraphrases of each other. Therefore We saw her duck is ambiguous."
      from Ohio & very colorful… like a submarine

    3. I meant it genuinely--I'm a receptive vessel for new vocabulary. Capaciousness is my middle name.

    4. This comment has been removed by the author.

  8. Let’s not forget our non-polar friends the flamingos who attain their (often brilliant) color due to their diet. They are born white or grey but turn pink because of eating shrimp and other foods loaded with carotenoids.

  9. Hello everyone

    Regarding the 2nd question, I began with [latitudes and animal size chart].
    On the Search Engine Results Page (SERP) was a link to
    Are latitudinal clines in body size adaptive?
    Skimming that manuscript mentioned several other papers that support latitude and size, but pointed out that beyond the obvious and broad label of latitudes other factors should be considered.
    "However, latitude itself is not of interest as it merely represents a geographic location on a map (Hawkins and Diniz-Filho 2004). Rather, it is the environmental and ecological variables that change with latitude (or any geographic location) that are of interest."

    Looking back at the SERP there were several mentions to Bergman's Rule that were cited in the study above.
    Many of the results were not recent so I used the Tools to limit it to results from the last year. On that SERP were results for Bergman's Rule applied to anthropology stating "That “rule” is no longer acceptable science and has nothing to tell us about physiological anthropology." Bogin, B., Hermanussen, M. & Scheffler, C. Bergmann’s rule is a “just-so” story of human body size. J Physiol Anthropol 41, 15 (2022).
    Also an animal trait database that was published in June 2022 that someone might use to study this further. Herberstein, M.E., McLean, D.J., Lowe, E. et al. AnimalTraits - a curated animal trait database for body mass, metabolic rate and brain size. Sci Data 9, 265 (2022).

  10. language bits - more for Dan - if he hasn't already seen…
    substack article