|Killer dolphins may be born of frustration|
|Wednesday, 01 June 2011 17:33|
Seemingly random acts of violence by bottlenose dolphins on porpoises could be down to sexual frustration among young males.
Cases of the cetaceans killing other creatures for no apparent reason have been reported in UK waters. Now, bottlenose dolphins have been seen attacking harbour porpoises in the Pacific Ocean. Crucially, these observations, published in Marine Mammal Science, show for the first time that the attackers are young males.
Mark Cotter at Okeanis, a non-profit conservation organisation in Moss Landing, California, USA, and colleagues, observed three acts of aggression by dolphins on lone porpoises.
The dolphins chased the porpoises at high speed, rammed and then drowned them. In one particularly violent attack, three dolphins corralled their victim before seven others joined them to ram the porpoise to death. Cotter found most shocking the fact that two dolphins remained behind to play with the carcass before pushing it towards his boat.
“It was almost like they said: ‘We’re done playing with it, here you go’.”
Competition for food does not seem to explain the attacks, as the dietary overlap between the two species is small, said Cotter. But the fact that 21 of the 23 attackers were males may be revealing. He believes that the attacks are “object oriented play” during the breeding season by young males who cannot get access to females because of competition from older males.
“They are taking out their frustrations,” he said.
“The identification of the ‘culprits’ as male is valuable,” said Nick Tregenza, an adviser to the Marine Strandings Network in Cornwall, UK, and visiting researcher at the University of Exeter. That’s because it helps narrow down potential explanations for the behaviour, he said.
Latest Book Reviews
- The Woodhen: A Flightless Island Bird Defying Extinction
- Casualty Management Guidelines
- Sustainable Coastal Management And Climate Adaptation
- Landsdorff And The Battle Of The River Plate: Command Decisions
- Commercial Practice In Bunkering
- Circle Of Treason: A CIA Account of Traitor Aldrich Ames and the Men he Betrayed
- A Sailor’s War
Latest CommentsRob simm: How does seeing a vessel operating outside of Australia in Sakalin, have anything to do with the MUA...
Dan Westerlund: To be noted that bigger (wider) ships can be built in Turku than in Papenburg. There have been negot...
Richard Stretch: Hi I am looking for information regarding Robert Farquhar.He was working at Walkers Limited earley i...
David Benn.: What is the best metal to use for building equipment to be used on oil rigs in the north sea. Corros...