Dolphins, long considered the world's most intelligent, sensitive and sociable creatures, have a secret: they can also be wanton killers:
The first was initially believed to show a dolphin fishing for salmon - until closer examination revealed a relentless attack on a porpoise, its body spinning round with such force that its back was broken and its soft tissue shattered.
Marine experts now believe that these displays of attacks on non-rival, non-predatory, peace-loving porpoises and, more shockingly, of dolphin infanticide, may have always taken place.
It is only now, with dolphins' more human-friendly behaviour taking them closer to tourist boats and beaches, that the violence is being witnessed first hand. Until the shocking realisation, dolphin-watchers in America had believed they were watching the mammals at play with their young.