Emperor Penguins and their orderly, civilized huddle

We all know and are amazed by the behavior and biology of the male Emperor Penguin, each prospective father incubating his one egg through the most brutal winter on this planet by protecting it atop his feet for months while not eating or drinking, only able to shuffle slowly as the winter ebbs and flows. It turns out that these elegant gentlemen are at the same time very polite and orderly as they stand incubating, rotating through huddles where each animal gets a turn amid a warming group of birds. This is so very civilized and orderly of these fine birds. I read somewhere some years ago that in the midst of the emperor penguin huddle temperatures can reach as high as 70°F. If so, the birds in the middle would need to rotate out just to not overheat. I suspect that as well they pack tighter or looser depending on how story, windy or cold it is.

There is a time lapse video of the huddle along with the article:

http://www.wired.com/wiredscience/2011/06/penguins-shuffle-warm/
Emperor Penguins Rotate Through Giant Huddle for Warmth

Massive huddles of male Emperor penguins are crucial to keeping warm during Antarctica’s brutal winter while they incubate their eggs.

These tightly packed penguins shuffle en mass every 30 to 60 seconds, reordering themselves so every individual gets to cycle through the warm, central part of the huddle.

The trick with these groups is to get the packing just right. If the penguins are too loosely arranged, they won’t stay warm enough, said Daniel Zitterbart, Barbara Wienecke, James Butler and Ben Fabry in a June 1 study in PloS One. But if they’re too tightly jammed together, they can’t rearrange themselves, and animals on the edge of the huddle won’t get a chance to warm up.

By taking small, 2- to 4-inch steps every minute or so, the penguins achieve maximum packing density. It’s like tapping on a can of flour to jiggle everything into the bottom.

But the shuffling also results in a wave of movement that rolls through the group and rotates every bird through the warmest parts of the huddle. Penguins can join the group on one end, cycle through the huddle and exit on the other end.

This creeping movement also means that different groups can merge into larger huddles.

The international team of researchers kept track of emperor penguin groups near a German research station in Antarctica using time-lapse photography. While charting the path of individuals over a four-hour period, the authors found that when the huddles remained still, they were tightly jammed. But once the shuffling wave started through the group, individuals ended up creeping their way through the huddle.

The authors found that individual penguins don’t change their position relative to their neighbors, nor do they force their way into or out of a huddle. The small steps the birds take are sufficient to move everyone around in a coordinated fashion.

The scientists still don’t know if one or more penguins start these waves of movement, or whether they follow any kind of hierarchy among individuals.

Penguins manage muscle oxygen supplies while diving

Penguins are clever creatures --- turns out they adjust their oxygen consumption based on how they are diving. Great stuff!

Penguins' Oxygen Trick: How They Survive Deep Dives
Jennifer Welsh, LiveScience Staff Writer ~ 12 May 2011
http://www.livescience.com/14117-penguin-diving-feat-oxygen-trick.html

And a very nifty graphic:
http://www.livescience.com/14125-deepest-divers-emperor-penguins-ocean-life.html

Penguins are the acrobatic athletes of the seas, and they can keep diving for long periods of time because they have exquisite control over how and when their muscles use oxygen, new research indicates.

The penguins can switch between two modes of oxygen use — either starving their muscles or giving them an extra shot of oxygen to keep them working — to achieve their amazing dives.

"It appears that there's a little bit of plasticity or variability in what they do when they are diving," said study researcher Cassondra Williams of the University of California in San Diego. "It's much more complicated than we thought."

To figure out how penguins survive deep dives on a single breath of air, the researchers designed special probes to monitor the levels of oxygen in the penguins' muscles during their dives off McMurdo Sound, Antarctica. The results are based on three emperor penguins and 50 dives, which ranged from 23 to 210 feet (7 to 64 meters) in depth, which lasted from 2.3 to 11.4 minutes.

"They have two different patterns they can opt for while they are diving," Williams told LiveScience. "In one, they appear to cut off blood flow completely to the muscle, leaving it to rely on its own supplies, which leaves the blood oxygen for the rest of the body, like the brain and the heart."

In other dives, the researchers saw a plateau after the initial oxygen drop. They believe that the penguin is selectively sending extra oxygen from the blood into the muscles, so they don't get tired. They can only do this for a limited time, though, until blood oxygen levels become too low for the rest of the body. Eventually the penguins need to come up for air.

Cutting off the oxygen supply to the muscles forces them to start making energy using "anaerobic" respiration, which is done without oxygen. It has a downfall, though; it produces abyproduct called lactic acid that can be toxic in high doses.

If the penguins let the lactic acid accumulate in their muscles, it takes longer to recuperate after a long dive, the researchers believe. This may be why on some dives the penguins send extra oxygen. For example, an extra oxygen shot might be beneficial if the penguins are taking several dives during a short stint to, say, chase down a school of fish and don't want to lose the feeding opportunity while they spend additional time on the ice recuperating.

"They don't want to hit their aerobic limit and accumulate lactic acid, but it's not clear how or why they do that," Williams said.

The study was published May 12 in the Journal of Experimental Biology.