I always found it amusing that people think that just because they have seen certain behavior in animals, it means this behavior is 'normal' or 'natural'. like profound evidence is some sort of absolute proof.
it's as if they believe mental illness, psychological damage from trauma, learned behavior, conditioning, responses to environmental variables, or other issues that can produce deviant behavior afflict humans exclusively.
just because you once saw a messed up animal exhibit a certain behavior, doesn't make that behavior normal or natural.