Short disclaimer: Before I continue, I just want to make it clear that I do NOT condone rape or find it humorous at all - whether it is done by a dolphin or anybody.
Dolphins do tend to be quite promiscuous in the wild, amongst other dolphins in their pod. Sometimes they....um...procreate with different partners, and from what I've heard about their sex lives, dolphins can be ready for a "roll in the hay" at a moment's notice. I don't know whether dolphins can distinguish that humans are not necessarily the same way. I think that's also why dolphin experts urge people to proceed with caution when they encounter wild dolphins, and to avoid getting bitten - dolphins also nip at each other either to assert their dominance, or just for fun, all the time; and they may not realize that what a fellow dolphin may regard as a simple, terse "leave me alone/I don't want to play right now" gesture or something all in fun might be harmful to a human being.
And Nick007, I also saw that episode of King of the Hill - as someone who is interested in cetacean behavior, I did find it intriguing. Prior to seeing it, I had no idea dolphins did that. I mean, obviously, it's not okay for a dolphin to take advantage of somebody, but what can you do?
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I wish Sterling Holloway narrated my life.
"IT'S NOT FAIR!" "Life isn't fair, Calvin." "I know, but why isn't it ever unfair in MY favor?" ~ from Calvin and Hobbes