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During the late 19th to the early 20th centuries, the whaling industry reduced the population of humpback whales across the globe to near extinction. But now, the large mammals known for their haunting songs may be bouncing back in some places. Recently, more female humpbacks in the Southern Ocean are giving birth to more calves, reports Karen Weintraub for The New York Times.
From 2010 to 2016, researchers collected skin and blubber samples from 577 humpbacks using a crossbow with modified darts. By sequencing DNA, the team determined that that population included a total of 239 males and 268 females. Higher levels of the hormone progesterone in the blubber showed that an average of 63.5 percent of those females were pregnant when sampled. But the story is in how those numbers changed, not the average.
The proportion of females increased from 50 percent to 59 percent during the six years. And the percent of pregnant females surged from 59 to 72, the researchers report in Royal Society Open Science. Altogether, the findings suggest “a population that is growing rapidly,” they write.