Why do spin­ner dol­phins spin?

BBC Wildlife Magazine - - Q & A - Sarah McPher­son

True ath­letes of the sea, spin­ner dol­phins are famed for do­ing just that – leap­ing out of the wa­ter in spec­tac­u­lar 3m aerial corkscrews. To per­form the pirou­ette, an in­di­vid­ual ac­cel­er­ates through the wa­ter with rapid pumps of the tail, then uses its mus­cle power to drive a tight twist as it breaks the sur­face.

Un­der­wa­ter, a spin­ner can gen­er­ate one to two ro­ta­tions per se­cond, but out in the open air it can per­form up to seven. The dis­play usu­ally ends with a re­sound­ing bel­lyflop.

The­o­ries abound as to why spin­ners spin. The be­hav­iour could con­vey a state such as hap­pi­ness, anger or fear; it may be a dis­play of dom­i­nance or courtship; it could be play, or a means of de­tach­ing par­a­sites and re­moras. The splash of the bel­lyflop may be a method of com­mu­ni­ca­tion, in­form­ing oth­ers near and far of an in­di­vid­ual’s po­si­tion in the wa­ter.

Spin­ning is ap­par­ently con­ta­gious – once one dol­phin gets go­ing, oth­ers join in.

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