Male bottlenose dolphins can reach a length of 13 feet and weigh more than 1,400 pounds, while harbor porpoises are among the smallest of the cetaceans, averaging about four feet, nine inches and 130 pounds. Worse for the reputation of the bottlenose our pals from the movie Day of the Dolphin and the television series Flipper scientists don't believe the two species compete for the same food. It's not territorial, but apparently a form of deadly bullying play. Observations in both Virginia and Scotland confirm that male bottlenose dolphins often kill newborn calves in the same way. Infanticide is a common reproductive strategy among mammals, especially in those species, such as bears, lions, and dolphins, in which females are not sexually receptive while rearing young.
Female dolphins become sexually attractive to males within days after losing a calf.
In fact, people who have been in the water with wild dolphins have been bumped, rammed, bitten, and in at least one case even killed by dolphins. The permanent smile on the faces of some species of dolphin is purely anatomical, no more indicative of the animal's state of mind than are the tusks on an elephant. I received half a dozen copies of the Times article by mail, fax, and e-mail from those friends who know that I have been working on an IMAX documentary about dolphins and collaborating on a companion book for National Geographic Books. The scientists among my correspondents and there were many, all of them consultants on either the book or the movie project found the article highly sensational and the headlines especially inflammatory. It isn't that we were unaware of the information in the Times piece or that any such material had been omitted from my book.