For some dolphins, pregnancy is a drag
When bottlenose dolphins swim - at a cruising speed around 6 mph or a sprinting speed about twice that fast - they are constantly fighting against the water's drag, which only gets worse as they swim harder.
Shawn Noren, a marine biologist at the University of California in Santa Cruz, set out to find how much extra drag would be experienced by a specific, aerodynamically disadvantaged subset of the dolphin population: adult females nearing the end of pregnancy.
Dolphins - which, like cows, descended from ancient ungulates - have their calves one at a time, after a 12-month gestation period. Over the course of pregnancy, a female's belly will grow until her girth increases about 50 percent.
The result is a drastic increase in drag: When a dolphin is within weeks of giving birth, she will encounter the same amount of water resistance at a speed of about 4 mph as she normally would at a speed of 8 mph, according to Noren's analysis.
Pregnant dolphins also swim differently, making shorter but more frequent strokes.
Noren's research appears in the Journal of Experimental Biology.
Some galaxies
are recycling
Using the Cosmic Origins Spectrograph aboard the Hubble Space Telescope, researchers have identified vast "halos" of gas surrounding a selection of 40 galaxies. Previously invisible, these halos are much larger than previously believed and act as reservoirs for recycled "star stuff" - light elements such as hydrogen and helium, and heavier elements like carbon, oxygen, nitrogen and neon. Also learned: Our galaxy has a halo extending up to 20,000 light-years from the Milky Way's disk, providing an explanation as to the mysterious source of gas that supplies our galaxy.
news.discovery.com
Muriqui business: 'Meet my brother!'
The muriqui monkeys of the Atlantic Forest in Brazil, a highly endangered species numbering only about 1,000, live in an egalitarian society.
Females are as muscular as males, so there is no threat of physical subjugation. Males, eschewing any kind of pecking order, do not compete to be alpha monkey. Even when it comes to mating, males tend to simply wait their turn instead of fighting.
Karen Strier, an anthropologist at the University of Wisconsin who has been observing muriquis for 29 years, says she has always thought that in the absence of a social hierarchy, no individual male should be much more successful at reproducing than any other. To test this idea, she and a team recently used DNA analysis to determine who fathered each of 22 muriqui babies.
Their research, which appeared in Proceedings of the National Academy of Sciences, shows a male enjoys greater reproductive success if he shares an unusual physical closeness with his mother, or if he happens to be lucky enough to live with a sister or two.
Strier's team thinks these females may help their male kin learn how to behave appropriately around potential mates, or perhaps give them special access to prime mating opportunities. "Like you're out with your mom," she said, "and you run into her friend who has a really gorgeous daughter." (To a muriqui male, "gorgeous" means ovulating.)
New York Times
