diagrams showing ( a ) the preferred position of a dolphin calf beside its mother , and ( b , c ) water movements near a dolphin when it is ( b ) gliding passively forward and ( c ) swimming actively .
diagrams showing how animals in a group can benefit from the vortices generated by their leaders .
 swimming animals set the water around them moving , and flying animals generate air movements . other animals traveling with them 
 can save energy by exploiting these movements of the fluid medium ; similarly , a cyclist can save energy by riding close behind another . 
 a new study of dolphin mothers and calves exemplifies the advantages of moving in concert . 
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