Female dolphins more likely to use sponge as hunting accessory than males

December 10th, 2008 - 2:52 pm ICT by ANI  

London, December 10 (ANI): A review of data gathered through several studies on dolphins suggests that males among them are less likely to be interested in learning to use a sponge as a hunting tool than their sisters.
It was in the 1980s that dolphins were first seen carrying sponges cupped over their beaks in Shark Bay, Australia.
Janet Mann and her colleagues at Georgetown University in Washington, DC, reviewed data collected during 20 years spent monitoring this group of dolphins.
The researchers observed that mother dolphins, though showed their offspring how to use sponges irrespective of their sexes, female calves were almost exclusively the only ones to apply that knowledge.
“The daughters seem really keen to do it. They try and try, whereas the sons don”t seem to think it’’s a big deal and hang out at the surface waiting for their mothers to come back up,” New Scientist magazine quoted Mann as saying.
Sponger dolphins shuffle their beak around in the sand, apparently, using the sponge as protection, and as soon as they ferreted out a hidden fish, they drop the sponge and catch the prey.
During the study, 11 out of the 19 dolphins born to sponging mothers were female and eight were male.
The researchers observed that 10 out of the 11 females, but just two of the eight males, became spongers themselves, generally within two to three years.
The study also showed that sponger dolphins generally tended to be loners, as they would spend over 80 per cent of the time on their own or with one calf.
The researchers also said that dolphins that used sponges as a hunting accessory did not seem to have a competitive advantage over those that did not, for females in both groups produced roughly the same number of calves.
Mann claims that her study is the first to look at the advantages that using tools brings to non-human animals.
“I think the finding that spongers have no fitness advantage over non-spongers despite supposedly higher costs is exciting,” says Michael Krutzen an expert in cetacean behaviour at the University of Zurich, Switzerland.
A research article on the study has been published in the journal PLoS One. (ANI)

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