There's a good one in Kate Millet's Sexual Politics about this guy Konrad Lorenz who came up with the idea of the "cichlid effect" to justify male agression in relationships with women (which JBP also does), a cichlid being a species of prehistoric fish which he examined "to conclude that the male cichlids failed to find the courage to mate unless the female of their species responded with ‘awe’. How one measures ‘awe’ in a fish is a question perhaps better left unanswered..."
I'm not sure what 'higher instincts' you'd attribute to dolphins. They're just slimy rape machines. Would love to smack one in the face, wipe that stupid grin off.
benny's right though, essentially - the argument is that X is a natural phenomenon, therefore X is - somehow - morally justified