Archive for May 2012
This week I am working on some fossil penguin bones from South Africa, and was reminded of the antics of Black-footed Penguins I have seen in zoos. Like most penguin species, they are surprisingly good jumpers, and this ability is subject to active research by marine biologists.If you have ever watched penguins swimming at eye level through glass walls at an aquarium, you may have noticed bubbles streaming from their feathers. It’s great fun to observe these birds zipping past like living Alka-Seltzer tablets. However, there is a point behind the bubbles, and a new study shows that releasing air at the right time helps penguins launch themselves out of the water.
Air has lower viscosity than water, so adding a layer of air around an object can help it cut through the sea more efficiently. Engineers have even applied this concept to make speedier torpedoes. Scientists studying film of diving penguins found that Emperor Penguins store air in their plumage, which gets compressed as they dive. Moving from deep water to shallow water lowers the pressure on the air, just like when one takes the cap off a bottle of soda. As the penguins near the surface, they are able to shift their feathers so as to release the air, which escapes in bubble form. This creates a smooth layer over much of the penguins plumage, which cuts down on friction and drag, allowing the penguin to build up a serious speed. An Emperor Penguin can reach velocities of up to 3 meters per second as it jumps out of the sea onto land. This may seem like fun and games, but when a bird needs to emerge from a hole in a thick sheet of ice or make it up a steep cliff, high speeds are critical. Check out some leaping penguins in action:
You can also read the original scientific article for free here.
Reference:Davenport, J., R.N. Hughes, M. Shorten and P. S. Larsen. 2011. Drag reduction by air release promotes fast ascent in jumping emperor penguins—a novel hypothesis. Marine Ecology Progress Series 430: 171-182.
Carbonemys was a big turtle. Here are two images that give a good impression of the size of the bones. Below, a line up of skulls shows how much larger the skull found near the Carbonemys shell is compare to the biggest side-necked turtles around today. This image has appeared with an NFL football for scale too, but the soccer ball (or REAL football depending on where you are from) seems a more appropriate scale object for a South American fossil.
The picture below is really cool, because it was not combined in Photoshop. Edwin was actually laying on a table next to the fossil, so the scale is exact. The only modification was whiting out the background!
Today I am breaking the all penguins rule at March of the Fossil Penguins to share a very special discovery. My graduate student Edwin Cadena studies another fascinating group of aquatic animals – side-necked turtles. Today, our paper on a new species of extinct turtle from Colombia hits the scientific newsstands. Carbonemys cofrinii was a behemoth of a turtle. It’s head was almost as big as a football and its shell was bigger than a person when stood on end. Edwin discovered this amazing fossil in a coal mine, hence the name “Carbonemys“, Latin for “coal turtle”. Carbonemys lived alongside many other reptiles in a sweltering swampland about 58 million years ago, several million years after the extinction that killed off the non-avian dinosaurs. Among these were smaller turtles, crocodiles, and the largest snake ever discovered – Titanoboa. Aside from leading the scientific paper that formally describes this new turtle, Edwin was the discoverer of the ancient shell. Other turtle remains from smaller species collected in the area have crocodilian bite marks, indicating they had to be wary of predators. Not so for an adult Carbonemys - crocodiles would have more to fear from the turtle than the turtle would from them.
Next week, it’s back to penguins, but today let’s celebrate this monster turtle.
Cadena, E.A., D.T. Ksepka, C.A. Jaramilo and J.I. Bloch. New pelomedusoid turtles (Testudines, Panpleurodira) from the late Paleocene Cerrejón Formation of Colombia and implications for phylogeny and body size evolution. Journal of Systematic Palaeontology.
Please stay tuned for a new fossil debut on Thursday – just to be clear, this won’t be a penguin. But I promise it will be cool!
A recent study looked at the chemistry of some ancient Adelie penguin eggs to understand where the penguins were getting their water – and thus learn more about their environment. Actually, these eggs are not too ancient by our standards. While many of the fossil penguin species we’ve covered on this blog are tens of millions of years old, the oldest eggs in this study are about 8,000 years old.
The scientists in this study looked at oxygen data from eggshell pieces. There are several “types” of oxygen atom called isotopes, differing by their number of neutrons. “Light” oxygen has 8 protons and 8 neutrons, and is known as oxygen-16 to scientists. “Heavy” oxygen has 8 protons but 10 neutrons, and is known as oxygen-18. One of the interesting things about these isotopes of oxygen is that they are treated differently by natural processes and end up getting sorted, or fractionated. Water of course has one oxygen atom per molecule, hence the formula H2o. Water with light oxygen evaporates more rapidly than heavy oxygen, which ends up leaving a chemical signal of where it came from. Water in the oceans tends to have more heavy oxygen in it, while snow tends to have more light oxygen, because it is made up of evaporated water that has returned from the sky as snowflakes.
Oxygen contributes to other molecular besides water, and one of these is calcium carbonate (CaCO3). Calcium carbonate is an important component of eggshells. Penguins, like all birds, shell their eggs with calcium carbonate. Oxygen from water sipped by the mother penguin gets added to the calcium carbonate of the egg, and thus leaves a trace of their water source behind when they lay the eggs. Scientists can collect fragments of hatched eggs and analyze them to figure out what the ratio of heavy to light oxygen tells us about the penguin’s water source.
Penguins are very good at getting water. There are no water fountains or bottles of sparkling water in Antarctica, but that poses no problem for Adélie penguins. Like other species, they are able to drink directly from the ocean while at sea, removing the salts through specialized glands to make the water usable by their bodies. On land, these little penguins have a habit of eating snow. This behavior is very useful in sub-zero temperatures where liquid water is impossible to find on land. However, it can get penguins in trouble in the wrong environment, as we saw when Happy Feat the stray Emperor Penguin tried to eat some sand thinking it was snow. In the video below, you can see a Chinstrap “drinking” some fresh snow.
In the new study, there was evidence that the older eggshells had relatively more light oxygen atoms. This indicates the penguins were probably munching on more snow or drinking more from freshwater streams in the past. Samples younger than 2000 years show an increase in heavy oxygen, indicating that the more recent generations of penguins at the colony have relied more on seawater and less on freshwater and snow. This makes sense when we look at whats happening on a large scale. Starting around 2000 years ago, there was probably less glacial meltwater available to drink. It’s also possible that changes in climate led to there being a larger distance between the penguin colony and edible snowdrifts than in the deeper past. Without a convenient snow snack nearby, the younger penguins probably waited until the next foraging trip to the sea to replenish their water supply.
Lorenzini, B.S., I. Baneschi, A. E. Fallick, M.C. Salvatore, G. Zanchetta, L. Dallai and C. Baroni. 2012. Insights into the Holocene environmental setting of Terra Nova Bay region (Ross Sea, Antarctica) from oxygen isotope geochemistry of Adélie penguin eggshells. The Holocene 22: 63-69.