Boundary Waters BWCA Snakes swimming in or on water is pretty much the same as fish swimming: retrograde body wave, acceleration reaction = thrust. Serpentine movement: refers in snakes to throwing the body into waves

Serpentine Locomotion S-shape movement (undulatory locomotion) Starting at the neck, a snake contracts its muscle series, thrusting its body from side to side, creating rearward travelling body waves (retrograde) In water below the surface, this motion easily propels a snake (or an eel) forward because the water completely surrounds and offers resistance. On land, a snake must find resistance points in the surface -- such as rocks, branches or dents and uses its scales to push on the points to thrust it forward.

Brown blunt-headed tree snake If as a snake you climb trees and vines for a living you are working with an interrupted substratum. Snakes have no problem climbing through the forest and points of contact become obvious.

Contact points are where the forces are transmitted for acceleration reaction.

Serpentine movement Depends on the projections from the ground so the body of the animal can be engaged Every part of the animals body is gliding forward, continuously All frictional forces acting between ground and body: only due to the axial muscles of the body

Relationship between sinusoidal motion of the body and the axial muscles to propel the animal forward: 3 adjacent segments of the body as rigid rods hinged together Each rod processing transverse processes for the attachment of elastic elements operating about the hinge Moves by altering the length and potential energy of the elastic elements …Contraction or relaxation exhibited by the muscles varies at different points along the body Serpentine movement (Gray, 1946)

ANACONDA

Rectilinear This technique also contracts the body into curves, but these waves are much smaller and curve up and down rather than side to side When a snake uses caterpillar movement, the tops of each curve are lifted above the ground as the ventral scales on the bottoms push against the ground, creating a rippling effect similar to how a caterpillar looks when it walks

Concertina The snake extends its head and the front of its body along the vertical surface and then finds a place to grip with its ventral scales It bunches up the middle of its body into tight curves that grip the surface while it pulls its back end up; it then springs forward again to find a new place to grip with its scales.

Sidewinders have been selected to lift part of the serpentine wave they put into acceleration reaction. Only certain portions of the body wave are placed in contact with the substratum

Sidewinding In environments with few resistance points (or where the sand is hot in the sun) snakes may use a variation of serpentine motion to get around Contracting their axial muscles and flinging their bodies into an S-shape that only has two points of contact with the ground When they push off, they only do so where they will move laterally. Half of a sidewinding snake's body is off the ground while it moves

Crotaline or ‘side- winding’ movement in snakes Challenging test question: could a snake employ sidewinding while swimming in the water column? Dr. Morris’s way of explaining it.

Crotaline locomotion in snakes: sidewinders A retrograde wave passes along the animal’s body, developing thrust in the head-first direction. As with serpentine body movements there are both lateral and forward force vectors (the latter force being the thrust). Normally in straight-ahead locomotion the lateral components of the resolved force vectors cancel: right to left and left to right vectors are in a sense ‘wasted’ motion. But sidewinding snakes use one of the sets of lateral forces (left or right) to push themselves sideways: thus they lift body regions clear of the substratum whenever the body wave there is developing lateral forces to one side, and so only the lateral forces driving to the other side act and push the snake laterally. *Socha J.J Of snakes and robots. Science 346: 160. Marvi H. et al Sidewinding with minimal slip: snake and robot ascent of sandy slop es. Science 346: Interesting recent paper on robots and sidewinding and biomimcry, the latter being human engineering inspired by an organism.

Robot that can’t ‘sand climb’ sheds light on how sidewinding is adjusted by sidewinding snakes for ascending sandy slopes Sidewinding upslope the snake ‘rolls and peels like a wheel’… ‘maintaining static rolling contact’. Robot ‘Elizabeth’ archaeological mission Egypt; when exploring up a sandy slope in a room it failed miserably, slipping and pitching over. Experiments with a tiltable bed of ‘air-fluidized’ sand: levels experimented with to 20 degrees from flat. Snakes deal with these increased slopes by increasing the length of body contact with the sand. Yield: “Yield occurs when the deformed sand cannot return to its original state when the force is removed.”

J J Socha Science 2014;346: Published by AAAS Sidewinding explained. Rather than moving in the direction of the head as do other snakes ( A ), sidewinding snakes move sideways both on level ground ( B ) and up slopes ( C ). Marvi et al. show that when snakes sidewind up a slope, they increase the body length that is in contact with the ground, thereby reducing slip.

Flying Snakes

Sphagniana sphagnorum Power amplified stridulation by a Canadian katydid

Katydid and cricket sound generation File teeth on the left tegmen engaged from below by a scraper ridge on the right View of katydid file File

Disengagement Free decay Driving Force involved Crickets song at 5 kHz) High Q Low Q At the right speed each file tooth corresponds to one wave. Crickets make sounds at 4500 teeth per second.

Teeth can be contacted at much higher rates than 4500 per sec. This predatory katydid (nr Arachnoscelis) from the lowland rainforest of Colombia strikes file teeth at per sec! It achieves this by catching bending and suddenly releasing a scraper. Elasticity contributes an lunge forward over a series of teeth. This is an example of power amplification.

nr Arachnoscelis high ultrasonics by elastic means

Patek S.N., Dudek D.M., Rosario M.V From bouncy legs to poisoned arrows: elastic movements in invertebrates. J. Exp. Biol. 214: Odontodactylus scyllarus, peacock mantis shrimp

Mantis shrimp are Crustacea: a major group of Phylum Arthropoda, the Order Stomatopoda ~300 species. All are marine predators of fish, crabs, shrimps molluscs. This photo is of Gonodactylaceus falcatus Great range of species sizes, 5-36 cm; they have highly developed eyes as one might expect of a predator that must aim a stunning strike at its prey. Zack T.I. et al Elastic energy storage in the mantis shrimp’s fast predatory strike. J. exp. Biol. 212: See Patek labsite: >

Zack T I et al. J Exp Biol 2009;212: ©2009 by The Company of Biologists Ltd Second pair of thoracic appendages are raptorial: they hit and stun prey. Moving distad on the limb (see B): merus (m), carpus (c), propodus (p) and dactyl (d). Between the merus and carpus is a skeletal limb segment: the ‘meral V’. It is associated with an internal VENTRAL BAR, a ‘mineralized’ region analogous to a leaf spring that is adapted to store elastic energy. Power amplification is achieved by meral-V latches that hold the metacarpal joint fixed during extensor muscle contraction. With the latches engaged, the contracting extensor muscle compresses the merus along its long axis. Sudden latch release brings the ventral bars back to unstressed shape which forces the carpus, propodus and dactyl to extend with high acceleration.

During preparation for a strike, the merus moves from its resting position (solid outline) to a compressed state (overlaid colors) that was mimicked by our materials testing apparatus. Zack T I et al. J Exp Biol 2009;212: ©2009 by The Company of Biologists Ltd