Tuesday, June 5, 2012

Why Spinner Dolphins spin




The spinner dolphin is known for its incredible leaps out of the water during which they can spin up to seven times.  Until 2005 no studies should evidence explaining why the dolphins spun in the air, but it had been proposed that the spinning could possibly help with the removal of unwanted remoras.  In 2005 Frank E. Fish, Anthony J. Nicastro, and Daniel Weihs conducted an experiment that supported this hypothesis.  Using mathematical models they showed that spinning would be extremely helpful in the removal of remoras.

Normal jumping does not move the remoras because they are still parallel to the dolphins body causing them to feel minimum drag upon reentry into the water.  However, spinning causes the remora to become perpendicular to the dolphins body thus causing a significant increase in drag upon reentry.  This resulting drag is the force that dislodges the remora.

http://jeb.biologists.org/content/209/4/590.full.pdf