Article today (2/23/2015) at vox-dot-com cites Cecil on mad rapist dolphins!
7 adorable animals that are also murderous monsters, Dylan Matthews, Feb. 23, 2015
Justin Gregg himself does not refute Cecil’s allegations so much as define “rape” in a way that precludes dolphons from being convicted of it.
Gregg is NOT saying, “There is no proof that horny, aggressive gangs of male dolphins try to force themselves on females.” Rather he’s saying, “When horny, aggressive gangs of male dolphins seem to force themselves on a female, we can’t read her mind, so it’s POSSIBLE she’s not really unwilling.”
And he may have a point. Look, when a new male lion fights and kills (or drives away) an older male lion who HAD been the proud possessor of a harem of lionesses, that new boss often kills the cubs of his predecessors, and re-impregnantes the cubs’ mothers as soon as possible. That’s cruel, but is it ““murder” or rape” the way humans define it? Maybe not. The lionesses don’t SEEM to grieve long for their lost cubs, after all, and don’t put up much (if any) resistance to the new male.
So, if a male dolphin kills a baby, figuring it may make its mother more receptive to his sexual advances, that’s cruel… but is it murder or rape? Does Mommy dolphin really love her baby or spend much time mourning for it? Or does she forget the baby quickly, go back into heat and willingly yield to the “creep” who killed the baby?
We don’t know. We can certainly say it WOULD look like rape if humans did the same thing. But no matter how smart they may be, dolphins and lions aren’t human, and can’t be judged according to human standards of morality.
Well, yeah, it’s just what dolphins do.
Did you see my recent post about the dolphin that pranked me? Any dolphin that does that gets to be judged by human standards of morality, sez I! 
(To be sure, that was a captive tame dolphin, not a wild dolphin out in the wild.)
ETA: And BTW, there are in fact anecdotes out there about dolphins appearing to grieve inconsolably over a dead baby.
This is quite common in the animal kingdom. After all, a male lion (or other animal) wants to see his genes passed to the next generation and doesn’t want to be wasting his time raising young that are not genetically his. The females may not do much because they understand the rules, or have their own reproductive strategy that says you lose this litter, but raise the next much more successfully.
Gray langur females will actively go out and court new males – even though if that new male takes over, they will kill the young if they feel that their male is getting old and losing his edge. To the female, if the male of the harem is losing his edge, it’s better for the young babies to be killed now when there’s not that much invested in them rather than raising them for three years, have a new male take over, and then have that new male kill a child you’ve wasted three years in raising.
In birds, it’s common to lay more eggs that can survive. Most of the time, the larger siblings will kill the weaker one by physically attacking it, and preventing it from feeding. However, when there is a surplus of food, both children may survive. Or if something happens to one chick, you can still raise the other one and not let a breeding season go to waste.