A squirrel climbing down a tree grips a ledge with a backward facing, double-jointed hind foot.

Over the Edge

There’s something remarkable in this photo.

At first, I didn’t see it. I was reviewing old photos and videos, and all I noticed here was the fungus growing inside the tree. Despite losing its top, this tree has provided nesting space for woodpeckers, wood ducks, and squirrels. But the fungus tells me our wildlife magnet is now so rotted, its shelter days may be winding down. So, the fungus inside the trunk is interesting, but that’s not what fascinates me about the photo.

Look carefully at the squirrel. He’s climbing head-first down the tree trunk. But what about the toes we see grasping the edge? Is that foot coming, or is it going?

Squirrels are notorious contortionists. Even so, we’re not seeing this fellow’s front feet climb up the tree as his hindquarters are headed down. The toes curled over the ledge belong to his hind feet. His double-jointed hind feet.

The technical term is hypermobility, and it means the squirrel has full flexibility to alter the direction of its rear feet. On level ground or climbing up a tree, the feet face forward, just like ours do. But heading down the tree, the squirrel will most likely pivot those feet until the toes face backward. That’s what you see in the photo, where the better-grip benefits of that pivot are crystal clear.

The video shows two short, slow-motion clips. Watch each squirrel’s hind feet and you’ll see the animals change foot positions as they travel.

Is it any wonder that squirrels are such talented seed stealers?

2 thoughts on “Over the Edge”

  1. What a sense of observation! I thought of your previous post yesterday, the one about the squirrels’ tail. There was a black squirrel on the top of your garage roof, totally immobile, except his head (safety first!) … and his tail. Inspired by your post, I tried to figure out why he was waving his tail like a flag. Checking the wind like you do, when you are sailing, with a wet finger… but the wind is not changing that frequently that you need to check it constantly. Waiving hello to his colleagues around. Flirting, like the peacocks fanning their trails… but it is not the season and there was no female… or male, around apparently!

    1. Squirrels use a technique called ‘tail flashing’ to signal alarm. They wave and flick the tail as a first-level alarm. If they feel seriously threatened, they add some vocals to the alarm. Third level: They run! And now you know that I’ve whiled away tons of time reading scholarly articles about squirrels!

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