Killer Dolphins!

The first recording of adult dolphins trying to kill a newborn of their own species has been made. The term is called infanticide, which means the practice of someone intentionally causing the death of an infant of its own specie mostly.

Infanticide is common in many mammal species, although it is rarely recorded among cetaceans. Until now, not many cases had been reported in bottlenose dolphins; but this new discovery suggests it could be more widespread than thought beforehand.
On the morning of December 5 2006 on Sepetiba Bay, Brazil, Mariana Nery, of the Southern University of Chile, and Sheila Simao, of the Federal Rural University of Rios de Janeiro, saw an experience they will probably remember the rest of their lives.

A group of six adult dolphins approached to a mother with her newborn calf. Two adults separated the baby from its mother. The female tried to reach the infant, but four other adults herded her, hitting her body and ramming her. Any attempt by the mother to escape was prevented by the pack, which chased her and blocked her path. Four meters away, the two remaining adults rammed the calf and held it underwater. They then threw it in the air and again pushed it underwater. Afterwards the calf swam with difficulty, and unlike the mother, was never seen again.

“Female dolphins become sexually receptive within a few days of losing a calf,” said Ms. Nery. That, and the sexual interest shown by the group in the mother, suggests they killed the calf for similar reasons.

There have been recorded cases of gangs of dolphins also killing baby porpoises, tossing them in the air and pursuing them to the death, similar to the killing of the baby dolphin. Marine experts believe these displays of attacks on non-rival, non-predatory, peace-loving porpoises may have always taken place, even though it was just recently discovered.

A theory had been made on the reason behind the porpoise murders, which included territorial clashes and feuds over food resources. But food is not in short supply and the porpoises are not just chased away, but pursued to the death.