The Dirt: This Week in Nature

Koala Males Woo Mates and Scare Rivals By Going Baritone.

It’s simple physics that shorter vocal tracts produce higher frequency sounds than longer ones. And since larger body size normally equates with longer vocal tracts, we are not surprised that a mouse squeaks but a lion roars. However, those cute, fuzzy koalas can produce some surprisingly deep baritone sounds for their size. Now researchers have figured out how they do it and have some theories about why. To get such deep sounds out of a relatively small body, male koalas have evolved specialized and unusually elongated vocal tracts that produce deep, resonating calls suggestive of a much larger animal. Researchers even suspect that a muscle in the koala’s chest functions to pull down the vocal tract to further increase its length. The resulting impressive baritone may be important to fend off and intimidate other males.

Read the full story at BBC Nature. In addition, if you ask any female koala, the body size of male koalas is an important mating consideration.

A Life-long Search for Dolphin Communication.

A New York Times science video explores the 25-year campaign of Denise Herzing, a marine mammal expert, to understand dolphin communication and ultimately to communicate with them. Dr. Herzing demonstrates the three main types of dolphin vocalization – whistles, clicks and burst pulses – and how we think they are used. The most challenging aspect of the work lies in the fact that much of dolphin vocalization lies in the ultra-sonic range, at frequencies well above what humans can hear. Ultimately, Dr. Herzing’s goal is to create a rudimentary human/dolphin vocabulary that can serve as a basis for inter-species communication.

Fish Uses Stone Tool to Open Clamshell.

The tool-wielding animal club seems to have another member. PopSci has published video of the orange-dotted tuskfish, which appears to search for an appropriate sized stone, carry it a considerable distance, and then put it to use to crack open a clamshell. The author cautions that other fish species demonstrate similar behavior, so one ought not jump to the conclusion that the behavior is learned.

Climate Change and the World’s Forests.

Forests worldwide seem to be under attack. In the New York Times Environment section, reporter Justin Gillis examines the complicated interplay between climate change, forest decline and forest re-generation. One thing seems clear: forests worldwide are being affected by climate-change induced agents, ranging from record breaking heat and drought to unprecedented beetle predation. And since trees are essential for locking up carbon dioxide, the stakes could not be higher. As the author puts it, “forests from the deepest Amazon to the remotest reaches of Siberia are now responding to human influences including the rising level of carbon dioxide in the air, increasing heat and changing rainfall patterns.”

Sharks Enjoy a New Refuge.

There have been many reports on how overfishing has resulted in the precipitous decline of shark populations worldwide. (Including some films we’ve done.) National Geographic reports on one island-nation that has done something to help the sharks. The Republic of the Marshall Islands recently passed legislation that creates a safe zone for sharks in a huge ocean area that is quadruple the landmass of California. The new law will punish shark fishing violators with heavy fines.

Much Maligned Dodos Actually Geniuses at Survival.

Because they could not flee from the humans who suddenly arrived on the island of Mauritania in the 1600’s, stories of the easy slaughter of these flightless birds soon made their name synonymous with lack of brainpower. But, Smithsonian Science reports that the reputation is undeserved. A recent carbon-dating study of Dodo fossils reveals that the birds were well adapted to the island on which they lived. In fact, the study showed that although hundreds of thousands succumbed to an extremely severe drought that decimated many of the island species about 4,000 years ago, the Dodos also survived. Nor should they be mocked because they were large-bodied and could not fly. Until humans hunted them to extinction, this peculiar physiology evolved as a successful adaptation that was particularly suitable to their environment, which included the absence of predators and long-term droughts.

Pressed for Time, Strange New Plant Buries its Own Seeds.

When it comes to survival, Mother Nature tries to leave as little as possible to chance. A new species of Brazilian plant has been discovered that can survive only in a few patches of suitable terrain and even there, it lives for only a few months. How to ensure the survival of the species? Plant you own seeds. In fact, the plant, named Spigelia genuflexa for its “genuflecting” stance, actually lowers its seed pods into the nearby soil thereby optimizing the chances that its seedlings will take root in just the right patch of soil.

Read the full story at Huffington Post.

Plants’ Carbon Dioxide Appetite Even Better than Previously Thought.

Measuring just how much carbon dioxide is removed from the atmosphere by plants is important for predicting climate change. Scientist may now have a new technique for measuring carbon dioxide absorption during photosynthesis. It relies upon tracking the two different oxygen isotopes that are contained in the carbon dioxide molecule. By comparing the ratio of the two isotopes, scientists have concluded that plants may actually utilize up to 25% more carbon dioxide during photosynthesis than previously believed. So, chalk up some welcome good news for planet earth.

Read the full story at Wired.

Wild Dingo Behavior Reflects Vestiges of Domestication.

Dingos had been partially domesticated in Southeast Asia for thousands of years. When they somehow were introduced into Australia some 4,000 years ago, they reverted to being wild animals that avoided human contact. A study comparing wild dingo behavior with that of wild wolves raises an interesting question. Why do dingos appear to react to human gestures, such as pointing, and facial expressions just like domesticated dogs, but wild wolves remain indifferent to human signals? An article in Natural History Magazine suggests an answer. It may be that, unlike the wolf, the specific dingo traits selected by humans during millennia of domestication have not yet been purged from the dingo population, despite their many generations in Australia as feral animals.

Earth’s Oceans Match Water Found in Some Comets.

In the debate over whether comets or meteorites contributed the water that forms the earth’s oceans, comets scored a win this week. On earth, the ratio between ordinary water, in which the hydrogen atom has only a proton, and heavy water (deuterium), in which the hydrogen atom contains both a proton and a neutron, is very specific. Up to now, scientists could not find a suitable earth ratio match from comet ice crystals. Now, according to National Geographic, scientists have determined that the Hartley 2 comet, which orbits near Jupiter, has a water/deuterium ratio similar to that of earth’s oceans. Moreover, since Hartley 2 originated in the Kuiper belt, which extends beyond Neptune’s orbit and contains many similar comets, a large part of the earth’s water could have come from comet collisions with early earth. Check out photos.