The Dirt: This Week in Nature

1. Piranhas’ Bark Announces Its Bite.

   Curious about why piranhas make a barking noise when they are removed from the water, scientists ran some experiments involving a fish tank, several piranhas and a piece of food. It turns out that piranhas can use the “swim bladder” in their bodies to produce two variations of a barking sound. The first bark is made when the fish are competing for food. The second seems to occur when they circle each other in the presence of food. Finally, a third sound, made by gnashing their teeth, tells competitors that the gloves are about to come off. The Scientific American podcast includes audio samples of these vocalizations.

2. 94 Million Years Ago, A Mouse Trap Would Not Have Been Enough.

   A fossil from South America is one of the oddest mammal fossils found to date. The find fills in a significant gap in what was previously known about mammal evolution in South America. The animal, now called Cronopio dentiacutus, lived around 94 million years ago and was the size of a mouse but had enormous and extremely sharp canine teeth and powerful jaw muscles to put them to good use. This extinct animal is from a family believed to be related to today’s marsupials.

   Read more at Red Orbit.

3. Inspiration from Nature May Have Robots Climbing the Walls.

   Scientists often have looked to nature for solutions to technical problems. One fascinating ability of insects is that they can climb walls, ceilings and just about any place else in seeming defiance of gravity. How they do it is not a secret. Tiny hairs on the bottom of their feet are known to provide amazing adhesive power and work on almost any surface. Using that same principle, scientists from the Zoological Institute at the University of Kiel, in Germany, have developed a sticky silicone tape that contains thousands of tiny silicon hairs. The tape can be reapplied repeatedly to various surfaces and, unlike other adhesives, does not lose its adhesive qualities. One possible future application for the new tape is to apply it to the bottom of the feet of search robots so that they can scale walls while they search for victims, weapons or bombs.

   Read more at Red Orbit.

4. Falcon Patrol Helps Vintners.

   Small birds enjoy the taste of grapes possibly as much as wine connoisseurs enjoy their wine. However, damage to vineyards by hungry birds is a problem for grape farmers. For a cost-effective solution, some have looked to nature. Falcons, those graceful raptors, are being deployed across California vineyards as a bio-friendly way to keep bird damage to their crops at a minimum. A falcon can patrol some 400 acres of crops and its very presence is enough to frighten away other birds. In order to enhance the deterrence value of the falcons, some owners have trained them not to kill and eat the birds they chase. As long as the falcon knows he has a bigger and better meal waiting for him at home, it will kill fewer of the birds it chases, leaving it more time to chase other birds.

   Read more at The Press Democrat.

5. Pas De Deux, Wren Style.

   Male and female plain-tailed wrens from Equador sing duets. By recording some 150 hours of songs from the birds and attaching electronic monitors to the brains of the animals, Eric Fortune of Johns Hopkins University was able to determine that each bird was not just singing its own memorized part, but in fact was reacting to the notes sung by its partner and replying in just milliseconds. The data reveal that both male and female birds responded most strongly to the female version of the song rather than the male version or the duet itself. This indicates that the female wren is the lead in the duet and that her sounds are parried by her male partner. The male bird does it best to respond to the particular notes with which the female leads, but the male does make mistakes, like dropping a note. Fortune says that the best analogy is two people dancing, where one takes the lead and the other follows step for step.

   Read more at Nature.

6. Animal Friends Defy “Birds of a Feather” Logic.

   Animals can make friends across species lines. In a photo gallery from Global Animal, there are some very odd animal friend pairings, including: a cheetah and a dog, a monkey and a dove, a bear and a cat, and a sheep and an elephant. The photos are based on the book, Unlikely Friendships: 47 Remarkable Stories from the Animal Kingdom, by Jennifer Holland.

7. Flying Rhinos! – Well, Sort of.

   In an effort to save the black rhino, the World Wildlife Fund teamed up with the Black Rhino Range Expansion Project in order to transport 19 black rhinos, by helicopter, from a poacher-susceptible area of South Africa to a safer location some 1,500 kilometers away. Because the trip by helicopter is so much shorter than by land transport, and so much less jarring, the animals can be given less tranquilizer. In addition, a new technique allows the rhinos to be lifted by their ankles, upside down, as they soar through the air en route to their new home. The photos, republished by the Huff Post Green, are worth a look.

8. New Addition to the Secretive Okapi Family.

   Okapis look like a mix between a zebra and a horse, but are actually related to giraffes. They are rarely seen in their native African habitats because they make exceptional efforts to remain hidden from other animals. For the first six months of its life, an okapi will avoid defecation just to limit its detection by other animals. Approximately 90 okapis are in American zoos, and one of the newest members, an 18-month-old calf named M’bura, made its public debut at the Bronx Zoo recently. Caring for a new-born okapi is especially difficult for zookeepers because of its parents’ secretive disposition. Zoo handlers cannot even give neo-natal exams because human contact with the young animal may cause its parents to reject it.

   Read more at the New York Times.

9. It’s a Bird, No It’s a Dinosaur … Archaeopteryx Continues to Perplex.

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   Whether the winged creature, Archaeopteryx, was more closely related to the dinosaur Velociraptor, of Jurassic Park fame, or to birds’ earliest ancestors, has been the subject of debate among paleontologists. In July of this year, the discovery in China of a chicken-like dinosaur led some paleontologists to suggest that Archaeopteryx, too, was probably a dinosaur with bird-like physical features. However, using an advanced statistical method called, phylogenetic analysis, Dr Michael Lee of the South Australian Museum has found that the creature is indeed more likely related to birds than to dinosaurs. Nevertheless, the fine line between early birds and bird-like dinosaurs will no doubt continue to perplex paleontologists.

   Read more at The Guardian.

10. Can Fish School Us on Driving in Traffic?

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    Hundreds of members of a school of fish can navigate effortlessly in the water, moving in unison, without crashing into each other or causing congestion. How do they communicate the information necessary for such high speed synchronization? It turns out that they follow very simple rules. Every individual fish reacts only to the fish in its immediate vicinity. For example, a fish accelerates or decelerates in order to keep a constant distance from the fish immediately in front of it, behind it and to its sides. This behavior is an example of emergent complexity – the tendency to evolve complex behavior by applying a few simple local rules. City drivers use similar techniques to avoid collisions on crowded urban streets, but much less efficiently. In the future, cars electronically programmed to behave more like schools of fish might make city drivers much safer.

    Read more at Discovery.

“The Dirt: This Week in Nature” curated and written by Robert Raciti.