Tufty E has his breakfast

June 6, 2014 • 4:35 am

There are two juvenile squirrels, but I haven’t been able to photograph them together. Here’s Tufty E enjoying a repast of sunflower seeds. Check out his magnificent tuft!  It’s interesting to see that the pattern of ticking in the fur gives their tails a stripey appearance. If it has an adaptive significance, I don’t know what it is.



16 thoughts on “Tufty E has his breakfast

  1. Is the striping on the dorsal surface of the tail? Probably not. With squamates (snakes, lizards), the striping effect has been suggested to have an antipredator effect because the striped pattern is difficult for a set of eyes to follow. While up in trees, where the squirrels sometimes sit with their tails above them, the different colors and markings would help blend into a shade mosaic and the tree leaves.

    1. Those markings in lizards also have the effect of attracting potential predators to their less vulnerable end, much the same way that the iridescent hindwing ‘eyespots’ in some butterflies (think hairstreaks and blues) do. Of course, lizards can readily drop their tails, to regrow them later, and butterflies can fly just fine, even after losing substantial portions of their wings. I don’t know how a tailless squirrel would fare, however.

  2. A little off topic but…

    Your comment on the striping of the tail brings to mind one event I attended some years ago, where there was two speakers, one an evolutionary biologist and the other a mathematically based researcher interested in patterns and self organization in biology.

    The mathematician was observing that butterfly wings are no a free canvas, where just any pattern can be painted. Patterns are constrained by the growth/development cycles that produce the wings. She discussed the famous ‘monarch pattern’ which has been replicated in a few species. Her suggestion was that this was more a matter of sharing a common development cycle than any strong selection advantage.

    The biologist argued strongly that this was selection that produced this cross species patterning, the mathematician then countered with tests that found no avoidance on the part of predators for the monarch pattern.

    The session quickly degenerated into a rather angry exchange.

    Of course the two suggestions are not mutually exclusive, but I guess people sometimes get a bit of tunnel vision.

  3. Chipmunks have a stripped appearance in their tails as well. Viewed from the back, the stripe goes all the way down in a loop.

  4. A spandrel? Related somehow to the shape of the tailbones, causing a clustering of hair follicles & resulting in the striping?

  5. Anti-landing strip. It looks like a cactus, which should be a fair stay away motivation. =D

    Though I assume Moran would say “adaptation is not proven, it’s near neutral fluff”.

  6. Could the striping be analogous (or maybe even genetically related) to agouti patterns in other mammals?

    1. Yes, “ticking” and “agouti” refer to the same sort of pattern in which hair color varies along the length of the hair.

      Wikipedia explains the genetics of tabby patterns in cats, including the so-called ticked tabby pattern (exemplified by Abyssinians).

      That still doesn’t tell us anything about the adaptive significance of such patterns.

      My guess is that the ticking is a side effect of some internal metabolic or hormonal cycle that causes different color genes to be expressed at different points in the cycle. We know that some mammals change their coat color seasonally; perhaps this is a spandrel or exaptation of that mechanism.

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