FYFD

Tag: animal locomotion

  • Overheating Slows Large Animals

    Overheating Slows Large Animals

    As climate change and human development continue to encroach on animals’ territories, mass migrations will become more and more common. But animals aren’t all equally able to travel long distances at speed. In general, larger animals are faster than smaller ones. But a new study shows that there’s another important factor in an animal’s top speed: heat dissipation.

    By studying the characteristics of over 500 animals that walk, fly, and swim, the team found that animals were limited in their speed by how well they could dissipate heat. This makes sense, even from a human perspective; we may be able to run long distances, but once we’re too hot, we have to slow down. The same principle holds for animals, and the bigger the animal, the longer it takes to dissipate heat. As a result, the team found that the fastest animals over long distances all have intermediate body mass. At their size, they can balance the mechanical ability to produce speed with the thermodynamic requirement to dissipate heat. (Image credit: N. and Z. Scott; research credit: A. Dyer et al.; via APS Physics)

  • Snail Locomotion

    Snail Locomotion

    Snails and other gastropods move using their single muscular foot and a viscoelastic fluid they secrete. Muscular waves in the foot run from tail to head and are transmitted to the ground through the thin, sticky mucus layer without the snail ever fully detaching from the surface. The characteristics of this mucus layer are critical to the snail’s locomotion. As a movement cycle begins, the mucus behaves like an elastic solid. As the muscular wave approaches, it shears the fluid, increasing its stress and ultimately reaching the yield point, where the gel begins to flow. Once the wave passes, the mucus quickly transitions back to its elastic solid behavior. The net result of each cycle is an asymmetric force that propels the snail forward while keeping it adhered to whatever surface it’s crawling on.

    Many animals rely on similarly complex fluids to move, attack prey, defend against predators, or enable their reproduction. Check out this review article for more examples. (Image credit: A. Perry; see also P. Rühs et al.; submitted by Pascal B.)

  • Review: “How to Walk on Water and Climb Up Walls”

    Review: “How to Walk on Water and Climb Up Walls”

    “An eight-year-old girl kicked her feet back and forth on the seat of a Long Island Railroad train. I beckoned her to cover over and pointed to the top of my winter jacket, which I slowly unzipped. Inside, nestling against me for warmth, were ten snakes, their forked tongues waving back and forth. The child shrieked and ran back over to her mother, who was napping. ‘That man has a coat full of snakes,’ she shouted.”

    So begins Chapter 2 of Dr. David Hu’s new book, How to Walk on Water and Climb Up Walls (*), a captivating and funny journey through animal locomotion and biorobotics. Don’t let that fool you, though; this book has plenty of fluid dynamics to it. Long-time FYFD readers will recognize some of the topics, such as the fluid-like behavior of fire ants, how eyelashes keep our eyes clean and moist, and why swimming behind an obstacle is so easy even a dead fish (like the one shown above) can do it.

    There are plenty of exciting, new stories as well, like how sandfish – a type of lizard – can swim under sand and why a lamprey’s nervous system may lead to better robots. The explanation of how cockroaches are virtually unsquishable and able to squeeze themselves into crevices a quarter of their height absolutely floored me. 

    Hu’s book offers a front-row seat to research at the cutting edge of biology, engineering, and physics, with anecdotes, explanations, and applications that will stick with you long after you put the book down. If you’re looking for a holiday gift for yourself or another science-lover, check this one out for certain (*).

    *Disclosures: I purchased my copy of this book using my own funds, and this review is not sponsored in any way. This post contains affiliate links – marked with (*); if you click on one of these links and purchase something, FYFD may receive a small commission at no additional cost to you.

    (Image credits: book – Princeton University Press; fish – D. Beal et al.; ants – Vox/Georgia Tech; eyelashes –  G. Diaz Fornaro; shark denticles – J. Oeffner and G. Lauder)