(Science Alert Australia & NZ)
(This coming in the same week when a contestant on the TV program "Jersey Shore," asked why the sea is salty, answered "Whale sperm?" The male whales might wish it so but apparently they have the same kind of luck dating that I do... oh, never mind. – Moderator MB)
Whaling disrupts mating system
Monday, 21 February 2011
By Rashelle Predovnik
Previously, people had thought that a
male sperm whale would take control of
of the group of females in his harem - but
this study found that the mating system
seemed to be determined by the females.
Image: lingbeek/iStockphoto
The mammal with the largest brain and the most powerful sonar system on earth has a culture that mystifies scientists according to marine biologist Professor Hal Whitehead.
The professor, who has spent the past 30 years studying the social organisation of sperm whales, says his research is challenging some long held beliefs.
It is well documented that sperm whales have complex social structures, their own dialects and different clans.
However Prof Whitehead says his research into sperm whale society became confusing when discoveries were made that did not make a lot of sense given the standard explanations biologists used to justify animal behaviour.
Eventually, his team concluded the missing part of the puzzle was culture.
"Culture as I see it is what individuals learn from each other and then they pass it on and it seems this is pretty important to sperm whales," he says.
Studies on social rites show female sperm whales travel in groups whereas mature males largely travel solo.
However, scientists have now discovered their comprehension of the relationship between the two sexes was completely wrong.
The historical belief that a male takes control of the group of females in his harem was debunked after researchers started following the females and a very different pattern emerged.
Instead of the male controlling the females, the mating system seems to be determined by the females.
"Some males are very successful because the females really like them and others not so successful because the females don't like them."
Significantly, he says, this has implications for the effects of whaling.
"The whalers and scientists assuming the harem mating system thought they could just leave one male with 20 females and that would be fine.
"So they went around killing a large proportion of big males and as they did this the pregnancy rates of the females started dropping."
When scientists studied this after at the end of whaling, they still found an extraordinary low rate of pregnancy in females in areas of very heavy whaling.
"What seems to have happened is the females didn't fancy some of the males left behind and the whaling had so disrupted the social system of the females that they weren't reproducing as they normally would," says Professor Whitehead.
"So this means whaling has implications far beyond the number of animals actually killed.
"The ones that survived weren't doing as well as they normally would and that's because their social systems were disrupted.
"There's a lot we don't know but what we do know is that the sperm whale has been put together in a rather extraordinary package."
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