Readers’ wildlife photograph

We have only two photos today, but they’re both lovely.

The first is a picture of one of my favorite bird species, the sexually dimorphic wood duck (Aix sponsa)—a striking instantiation of sexual selection: the coevolution of male traits with female preferences for those traits.

One wonders, as in all such cases, what features of that gaudy male gave him a reproductive advantage over other males—and why. Was it a marker of his better genetic endowment {the “good genes” model), a fortuitous pattern that appealed to pre-existing female biases, or some other reason? While the mechanism of sexual selection is well understood, the reason why some features appeal to female preference—and thus enhance both the male and female’s reproductive output—is poorly understood. In only a handful of cases do we know what advantage accrues to a female who chooses certain male traits.

This photo was taken by reader Nicole Reggia at Valley Green, Wissahickon Park, Pennsylvania.


And I’ve stolen this (with permission) from naturalist/biologist Piotr Naskrecki’s Facebook page, which showed this ethereal photo along with the caption below:

The early downpours in Gorongosa National Parkhave created a massive network of ephemeral ponds. They are now teaming with life and freshwater crabs (Potamonautes obesus) are everywhere.

Yes, it’s a photo, not a drawing:



  1. Posted November 11, 2016 at 8:32 am | Permalink

    Piotr’s photo is wonderfully evocative. Love this kind of photo, which artistically integrates its subject into its environment. Very hard to accomplish, as you need great depth of field but the light changes rapidly and the subjects move around.

  2. rickflick
    Posted November 11, 2016 at 8:56 am | Permalink

    The Wood Duck is certainly a remarkable bird. Didn’t Tara film these in the Everglades?
    It occurs to me that with a better understanding of brain function, a pattern matching the male should be observable as a neuronal map inside the female. The mental map would have evolved together with the male’s appearance. It seems plausible that the map would evolve influenced by preexisting biases in the female brain. This should be reflected in a certain amount of commonality between the males of several species.

  3. Andrew Laycock
    Posted November 11, 2016 at 9:30 am | Permalink

    Those ducks look almost translucent, as if they are made of glass.

  4. Posted November 11, 2016 at 10:23 am | Permalink

    To Piotr: typo – s/b “teeming with life”.

  5. HaggisForBrains
    Posted November 11, 2016 at 10:35 am | Permalink

    Crab, “Get off my lawn!”

  6. Heather Hastie
    Posted November 11, 2016 at 11:44 am | Permalink

    Both beautiful pics. Those wood ducks are gorgeous.

    HaggisForBrains comment above is just what I thought about the crab.

  7. Gregory Kusnick
    Posted November 11, 2016 at 12:07 pm | Permalink

    I seem to recall reading somewhere that sexual selection can be explained in selfish-gene terms.

    If a female who likes red eyes mates with a male who has them, then their offspring inherit both the red eyes and the preference for them. Red eyes then become a badge by which the prefers-red-eyes gene recognizes itself in potential mates: any male who has them probably had a mother who prefers them.

    So the initial preference can be essentially arbitrary, and needs no adaptive utility, because once it’s satisfied, a positive feedback loop kicks in to maintain selection pressure in that direction.

    • Posted November 11, 2016 at 7:53 pm | Permalink

      That’s one theory of sexual selection, called the “runaway” theory. But there are other theories as well, and the runaway may not work if there is a “cost” of female preference: having a preference may make you so picky that you aren’t as likely to find a mate if the right male isn’t around.

      • Gregory Kusnick
        Posted November 11, 2016 at 8:08 pm | Permalink

        That makes sense, but isn’t it just another way of saying that preferences are subject to a selective filter based on their likelihood of gaining a foothold? A female with a preference that can’t be satisfied suffers reduced fitness, but one with a preference that’s easily satisfied from within the existing range of male variation imposes a slight selection pressure on that variation, at negligible cost to her own fitness. The preferences that survive that filter are the ones that get amplified. So I don’t see that as an argument against runaway sexual selection.

  8. Mark Sturtevant
    Posted November 11, 2016 at 12:48 pm | Permalink

    The wood ducks photo does not seem entirely natural. My impression with the patterns and tones and colors is that this is a painting,or a least a photo whose colors have been adjusted.

    • Diane G.
      Posted November 11, 2016 at 10:29 pm | Permalink

      Yes, the blue tones are certainly exaggerated but maybe that was the photographer’s intent. Or the wrong white balance setting. 🙂

      Makes a lovely picture nonetheless.

      True colors:

  9. gravelinspector-Aidan
    Posted November 11, 2016 at 1:15 pm | Permalink

    One wonders, as in all such cases, what features of that gaudy male gave him a reproductive advantage over other males

    Sorry, but why am I thinking of the Commonly-Spotted Orange-tufted Quacker, Presides minimanus?

    • infiniteimprobabilit
      Posted November 11, 2016 at 3:09 pm | Permalink

      You almost had me there. I was about to Google it.



    • Diane G.
      Posted November 11, 2016 at 10:30 pm | Permalink


  10. Malcolm
    Posted November 11, 2016 at 2:43 pm | Permalink

    Am I being stupid but shouldn’t the ducks be brown? They are blue on my pc.

    • Mark R.
      Posted November 11, 2016 at 3:33 pm | Permalink

      Yeah, the photo has a blue/cyan cast…but still lovely.

  11. Mark R.
    Posted November 11, 2016 at 3:35 pm | Permalink

    That crab looks huge, but it’s probably small as I don’t think freshwater crabs grow very large. Beautiful image.

  12. Dale Franzwa
    Posted November 11, 2016 at 11:27 pm | Permalink

    Ok ladies, why is it only males commenting above on the nature of female attraction to certain males? Surely you must have something to add that might enlighten us long suffering males on the nature of female attraction to some males and not others of us? I bet the word “cute” figures in there somewhere. Why are you laughing?

    • Diane G.
      Posted November 12, 2016 at 12:09 am | Permalink

      Consider aping the sage grouse–puff out your chest, strut around, make weird pops and whistles and booms…oh wait, maybe the grouse got it from guys…

  13. frednotfaith2
    Posted November 19, 2016 at 6:21 pm | Permalink

    Beautiful photographs. The one featuring the crab certainly looks much like a semi-surreal painting.

  14. Posted November 25, 2016 at 1:57 am | Permalink

    Nice blog, following! very nice photos!

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