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Sharks and Rays

White Tip Reef Shark

The white tip reef shark (Triaenodon obsesus) is one of the three most common sharks on coral reefs. A relatively placid species, T. obsesus is capable of lying motionless on the bottom substrate for long periods of time, and is often found resting in caves (Randall, 1977). Site fidelity is strong with each shark maintaining a small home range for months or years at a time. The following footage shows the behavior and ability of T. obsesus to rest on the bottom of the substrate.










Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2003)

Randall, J.E. (1977) Contribution to the Biology of Whitetip Reef Shark (Triaenodon obsesus). Pacific Science 31(2):143-164.



Undulation vs. Oscillation

Batoid fishes (sawfishes, skates, stingrays) are morphologically analogous having dorsoventrally flattened bodies and greatly expanded pectoral fins. Batoids can be divided into two subgroups based on their method of propulsion through the water (for review see Rosenberger 2001): using the body and tail (axial-based locomotion) or large pectoral fins (pectoral fin-based locomotion). Pectoral fin-based locomotion has traditionally been divided into two further categories; oscillation and undulation. Undulation of the pectoral fins is defined by having more than a single wave present on the fins at a time (Webb 1994). Batoid fishes that use this method include most stingrays and skates. By contrast, oscillation of the pectoral fins has less than half a wave on the fins at a time (Webb 1994). This group includes the pelagic rays such as manta, cownose, eagle and bat rays. A recent study by Rosenberger (2001) showed that most species demonstrating pectoral fin-based locomotion fall along a continuum between undulation and oscillation. For example, the southern stingray (Dasyatis americana) exhibits both forms of pectoral fin locomotion determined by swimming behavior and speed. As their velocity increases they shift from the oscillatory to the undulatory form. The following footage shows D. americana exhibiting first undulatory and then oscillatory swimming patterns as they slow down; and the spotted eagle ray (Rhinoptera bonasus) demonstrating only the oscillatory behavior. Of the species studied, Rosenberger (2001) found that R. bonasus was the only species to exhibit strictly oscillatory behavior.

Credits
Cinematography: Dr. Forest Rohwer & Dr. Stuart Sandin
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2003) Palmyra Atoll, Line Islands, Central Pacific (2004)

Rosenberger, L.J. (2001) Pectoral fin locomotion in Batoid Fishes: Undulation versus Oscillation. Journal of Experimental Biology 204, pp 379-394.

Webb, P. W. (1994) The biology of fish swimming. In: Mechanics and Physiology of Animal Swimming (Ed. L. Maddock, Q. Bone and J. M. V. Rayner), pp. 45-62. Cambridge: Cambridge University Press.