Readers’ wildlife photos

Reader Christopher Moss sent a passel of baby spiders, a bird, and Eastern chipmunk babies:

Araneus diadematus [the European garden spider] I think. The nest is on the glass of my conservatory, here in Nova Scotia. It doubles as a greenhouse at this time of year so there’s lots of garden spiders in there. These are the kind where the nest ‘explodes’ if you touch it as all the baby spiders jump for their lives. After a few minutes they crawl back up their silken lifelines and you can’t tell that anything happened.

Two babies [Tamias striatus] emerged this morning, and while I didn’t catch them together on camera, they behave quite unlike the adults who chase each other aggressively. These two are still acting like nest mates and crawl all over each other!

Downy woodpecker (Dryobates pubescens). He comes and steals the squirrels’ food!

Tara Tanaka in Florida (Vimeo page here, Flickr page here)  has discovered that she actually has two bobcats on her land: the one I posted about a week ago, which turns out to be a female (now named Bobera), and a male. The female appears to be denning nearby, and let’s hope we see BOBKITTENS soon. Here’s the male, now named the real Bob. Note the testicles under the tail.

Does anybody know why these cats (and many felid species) have white spots on their ears, and a white under-tail? They must be used to make the animal visible from the rear, suggesting that it’s a signal to conspecifics or kittens, but I don’t know.

20 Comments

  1. Posted June 16, 2018 at 8:28 am | Permalink

    Squirrels also have white behind their ears, but I think only in winter. That doesn’t sound like a signal to young. But, of course, the similar color may have different significance in bobcats and squirrels.

  2. Linda Calhoun
    Posted June 16, 2018 at 8:36 am | Permalink

    “Does anybody know why these cats (and may felid species) have white spots on their ears…?”

    Because their parents did?

    L

    • Posted June 16, 2018 at 9:46 am | Permalink

      That’s the proximate rather than the ultimate (evolutionary) explanation! 🙂

  3. Ben Yandell
    Posted June 16, 2018 at 9:28 am | Permalink

    Many cat species have these pale spots on their ears. I’ve always thought these were fake eyes, reducing the chance of attacks from the rear (which felines often employ).

    Rangers in India apparently wear fake eyes on the backs of their hats to ward off tiger ambushes.

    • David Harper
      Posted June 16, 2018 at 9:56 am | Permalink

      Does that actually work for the rangers? I’d be surprised if a tiger were deterred from attacking a human just because it thought the human was staring at it.

      • nicky
        Posted June 16, 2018 at 10:51 pm | Permalink

        Apparently it does, it was developed in the Sundarbans and locals wear them. It is said that tiger attacks have diminished since

        • nicky
          Posted June 16, 2018 at 11:31 pm | Permalink

          Synodontis nigriventris ‘black -bellied’ was the one I was referring to, not ‘versicolor’. Apparently there are even several species of upside-down catfishes.

          • nicky
            Posted June 17, 2018 at 12:39 am | Permalink

            Wrong Place, this should have been at no 7, Sorry.

        • nicky
          Posted June 17, 2018 at 12:47 am | Permalink

          The official study was only over a year (November 1986 to October 1987), and it appeared to work very well.
          https://i.publiclab.org/system/images/photos/000/011/653/original/Tiger_Mask.pdf
          However, there are some reports (unreferenced) in eg. Wikipedia, that the tigers are no longer fooled and that the masks don’t work anymore. I could not find an official report or study of the latter.

  4. DrBrydon
    Posted June 16, 2018 at 10:07 am | Permalink

    Well, the tail spot leads me to think that it’s a sort of signal. When the tail’s up, the cat isn’t in defensive mode, so it could signal all clear to others. I’ll go all in and say that the ear positioning is the same.

  5. rickflick
    Posted June 16, 2018 at 10:40 am | Permalink

    The white tailed deer and the cotton tailed rabbit are prime examples of white flags. When deer in a group decide to flee all at once, the flashes of white among the darker trees may be a way to confuse a predator, or a way to signal others in the herd that it’s time to scram.

  6. Michael Fisher
    Posted June 16, 2018 at 11:48 am | Permalink

    I think those ‘eye spots’ on the bobcat can show from the front when the cat so chooses – makes the head look much larger when facing off an aggressor.

    I saw a photo of a bobcat with ears swivelled to show the spots while it’s head was down drinking – perhaps to fool an ambusher.

  7. Steve Gerrard
    Posted June 16, 2018 at 11:55 am | Permalink

    Quite a few animals have white or light colored bellies, not just cats. The prevailing notion is that since light comes from above, having a darker color on top and a lighter color underneath counters the shadow effect, so the animal blends into the background better and is less noticeable.

    • nicky
      Posted June 16, 2018 at 11:01 pm | Permalink

      Yes, I though countershading was well established. Even lights at the bottom parts of deepsea fish. And then there is the mirror-effect in the scales of herring and other fish.
      All that does not explain the earspots and white tailbottom. The latter screams ‘signal’ to me, but of what is another matter.
      The reason for the white earspots is even more covered in darkness, but some valient attemps were made here.

      • nicky
        Posted June 16, 2018 at 11:03 pm | Permalink

        Think also of the ‘versicolor’ catfish that skims the surface upside down. Great evidence IMMO.

  8. Wayne Y Hoskisson
    Posted June 16, 2018 at 12:42 pm | Permalink

    The variation in dorsal vs ventral color is widespread in mammals. Bobcats and linx both tend to have light to white colored bellies although as far as I can tell there is a great deal of variation in coloring. I think flags developed from this dorsal/ventral pattern and may be just an add on. This does not make as much sense in bobcats since they tend to be solitary and signaling may not be very important. Evolutionarily the pressure to develop different top and bottom coloring must have come a long, long time ago or it could just be the result of pressure on patterns for embryonic development of multiple organs.

    I am just guessing and not an expert.

  9. Posted June 16, 2018 at 5:51 pm | Permalink

    Unfortunately, the bobcat kittens mistaken for domestic ones in Texas have died, of parvovirus infection:
    http://cbsaustin.com/news/local/bobcat-kittens-mistaken-for-domestic-kittens-die-at-animal-sanctuary

  10. Posted June 16, 2018 at 6:32 pm | Permalink

    Perhaps these white spots have something to do with cooling “vents” at the extremities.
    They face backward as to not to interfere with the camouflage?
    In birds i have read and perhaps it applies to other animals, in the case of white “rear ends” it is a way to select for health in the mating game of sexual selection.
    Dirty butt clearly seen may mean gut parasites, etc. and nice clean butt, I’m good how you doing?

    • nicky
      Posted June 17, 2018 at 5:08 am | Permalink

      The South African desert lynx, aka ‘Rooikat’ (litt. ‘red cat’) or Caracal, has big ears, darkish with a white lining and black tufts on top. I have no idea if that has any import on the white ear-patches in the bobcat.
      That their ears are disproportionally large indeed probably has to do with the hottish climate (you see the same, but even more outspoken, in the desert fox (Fennek). Thermoregulation? (your ‘cooling vents’). Do bobcats, living in cooler climates need cooling vents?
      They also have a white lining/patch around their eyes, as often found in night hunters, such as the lion. Typical daylight hunters such as the Cheetah have a dark line. below their eyes.

      • Posted June 17, 2018 at 5:21 pm | Permalink

        ah.. thanks for that, it was just a wild stab at it, i thought being white and at the extremes, reflecting to aid heat loss as opposed to absorbing. Cooler climes would probably negate the need for heat aids as you noted… back to the drawing board.


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