One of the distinctions between humans and animals is that we are a moral species. Only we create moral codes through rational means–which is one reason they differ from society to society.
Animals are amoral. Whatever morality they appear to show–often anthropomorphized by observers–comes from instinct, not rational discourse and deliberation worked out and changeable over time.
With that in mind, dolphins are often romanticized as gentle sweethearts. But males force females into situations of gang forced intercourse, and may kill unrelated young. From the BBC story:
Small teams of males were usually part of larger “super-alliances” of up to 14 males.
It is also clear that the females are not particularly willing participants. “Male aggression toward a consort included chasing, hitting with the tail, head-jerks, charging, biting, or slamming bodily into the female,” Connor and colleagues wrote in their 1992 paper.
The females frequently “bolted”, but only managed to escape the males once in every four attempts. “Over the course of the year, a female will be herded by lots of different alliances over many different months,” wrote Connor and colleagues
The males also apparently kill the young:
During 1996 and 1997, 37 young bottlenose dolphins washed up on beaches in Virginia. Superficially, there appeared to be nothing wrong with them, but necropsy revealed evidence of “severe blunt-force trauma”.
The injuries were mainly to the head and chest, “and multiple rib fractures, lung lacerations, and soft tissue contusions were prominent,” according to a study published in 2002. There was lots of evidence that adult dolphins were responsible for the deaths.
Notice I didn’t use the term “rape.” That is because an animal cannot commit rape, which is a crime that involves moral turpitude.
The dolphins forcing themselves onto unwilling females, and killing the young isn’t wrong. It is merely dolphins being dolphins.
Of course, when humans do such thing, they are judged rightly as monsters. That is because we are exceptional.