SCIENCE NATURE SCHEMES : BOWHEAD WHALES

 

A Pregnant Pause : A baby that takes time in making a first appearance.

Like other whales, bowheads are hard to study. '' We don't see most of their life, since they spend a fraction of it as surface, '' said Nadine Lysiak, a marine biologist.

'' Bowhead whales can live greater than 200 years, they go into sexual maturity late and it takes them a long time to grow, '' she said. And after nearly being driven into extinction by human hunters, these travelers in a warming Arctic are again at risk.

But Dr. Lysiak has peeled back some of the layers of aquatic secrecy surrounding bowheads.

After examining hormone concentrations related to pregnancy in 10 female bowhead whales collected by Inuit hunters in the eastern Canadian Arctic and West Greenland, Dr Lysiak and her colleagues have learned something extraordinary about bowheads.

They found that pregnant bowheads may carry their calves for 23 months. That would be the longest pregnancy in the mammalian kingdom, edging out elephants by a month.

It's a much longer pregnancy than the 14 months previous researchers had suggested.

'' I double and triple checked everything just to make sure I believed in the numbers and the timelines we were using, '' Dr. Lysiak said.

And yet, she said, both estimates could be right : One possible explanation for the unexpected patterns of hormone concentration they found could lie in a phenomenon known as delayed implantation,or embryonic diapause.

When a fertilized egg develops into an embryo, there's a point at which the mother's body can put the pregnancy on hold. It's considered a survival advantage that allows the mother's body to essentially decide when is the right time to have the baby.

Depending on the species, this pause can last anywhere from a couple of days to 11 months.

'' That is something that occurs in a lot of marine mammals, like seals, bears, otters, a lot of terrestrial animals but, until now, it's been discounted as occurring in baleen whales, '' Dr Lysiak said. [ Miriam Fauzia ]