Arizona Public Radio | Your Source for NPR News
Play Live Radio
Next Up:
0:00
0:00
0:00 0:00
Available On Air Stations
Science and Innovations

Earth Notes: Rattlesnake Tail Shaker Muscles

Google Images

When rattlesnakes warn you to back off, they hold their tails upright to help the rattling sound travel further. And visually reinforce that ‘stay away’ message by showing the striped part of their tails.

Those stripes are where rattlesnakes’ tail shaker muscles are located. And they contract up to 90 times per second - the highest frequency in the vertebrate world – and much faster than the 40 contractions per second of the flight muscles in a hummingbird’s wings.

Snakes sometimes continue rattling for minutes on end, so those tail muscles also have to perform like endurance athletes – and have evolved a fine balance between the three components. One third is devoted to switching the muscles on either side of the tail, on and off … extremely fast, to generate side-to-side motion. Another third consists of energy-producing mitochondria. Only the remaining third of the muscle produces force … or strength. So, although they’re fast – rattlesnake tail muscles are also quite weak.

But rattlesnakes have a clever energy-saving ‘trick’. Using their tail muscle like the extended rubber band in a sling shot, they harness the rebound energy of each muscle contraction to flick the tail over to the opposite side.

Unravelling and adapting this trick has led Northern Arizona University researcher Stan Lindstedt and his students to develop a patented device now being used in physical therapy clinics across the country. It looks a bit like a recumbent bike and works by making people have to slow the pedals down. This develops muscle lengthening contractions, allowing patients with muscle weakness to grow stronger gradually, with minimum energy.

Exactly the same way a wily rattlesnake … shakes its tail!