We already knew that great numbers of sea turtles are killed when they’re caught up in the nets used by fishing operations around the world. But according to a study in Conservation Letters, the actual number of turtles accidentally killed over the last two decades has been vastly underestimated: Rather than counting in tens of thousands, study author Bryan Wallace argues, commercial fishing has probably killed sea turtles in the millions.
The official records show about 85,000 turtles killed by fishing operations from 1990 to 2008. But Wallace, the science adviser for Conservation International’s sea turtle program, says that’s deceptively small accounting. “Because the reports we reviewed typically covered less than 1% of all fleets, with little or no information from small-scale fisheries around the world, we conservatively estimate that the true total is probably not in tens of thousands, but in the millions of turtles taken as bycatch in the past two decades,” said Dr Wallace [BBC News]. Six of the seven sea turtle species are presently listed as in danger. They include loggerheads, leatherbacks, hawksbills, Olive Ridleys, Kemp’s Ridleys and green sea turtles; the flatback, an endemic to Australia, is currently categorized as Data Deficient [CNN].
Some of the weird wildlife on Madagascar—its mammals especially—probably arrived there by rafting from mainland Africa, we reported back in January. But not its blind snakes. According to a study out now in Biology Letters, these funny-looking creatures date back 150 million years to the Gondwana landmass, and have lived on Madagascar since before it broke off from India and drifted away. And, the researchers say, their story of spreading around the world carries many more twists.
Growing to about a foot long, blind snakes act a lot like worms, burrowing under the surface of every continent except Antarctica. Unlike worms, though, blind snakes have backbones and tiny scales [National Geographic]. They earned their moniker by having blurry vision and sensing chemicals through their skin to find their way around. But despite having backbones, there are few blind snakes in the fossil record, making it hard for researchers to study their evolutionary history. So lead researchers Blair Hedges and Nicolas Vidal had to rely on living species. They extracted five nuclear genes, which code for proteins, from 96 different species of worm-like snakes to reconstruct the branching pattern of their evolution, allowing the team to estimate the times of divergence of different lineages using molecular clocks [UPI].
When it comes to picking up clever tricks and learning to do something the way everybody else does it, social animals like humans, birds, and monkeys excel. One individual looks at what others in the group are doing and quickly learns to follow suit—an invaluable skill that scientists previously thought evolved in step with communal living.
But what about an individual that doesn’t live in a group and spends most of its life in solitude–would it still have that ability to watch and learn? Cognitive biologist Anna Wilkinson set out to answer that question by studying the red-footed tortoise, one of the loneliest beasts on the planet. These South American tortoises grow up without parents or siblings, and adults rarely cross paths. If a head-bobbing display determines that a stranger is of the opposite sex, the two will mate perfunctorily–otherwise they just ignore each other [ScienceNOW]. Yet in a new study published in Biology Letters, Wilkinson showed that even these hermits possess the ability to learn by watching others.
Hot, cold, in between, it doesn’t really matter to chameleons: They’re going to snare their prey anyway, according to findings in this week’s Proceedings of the National Academy of Sciences. That’s because their elastic tongues are designed like ballistic weapons.
Chameleons fire their tongues at breakneck speed, says study leader Christopher Anderson. “A chameleon’s tongue travels at accelerations exceeding 400 meters (1,312 feet) per second squared, or about 41 Gs of force,” he added. To put that into perspective, a space shuttle only develops about three Gs of force when it takes off [Discovery News]. Given that muscle performance diminishes when it gets colder, and that these lizards are ectothermic (cold-blooded), one might think their tongue prowess would trial off sharply as temperatures drop.
Not so, Anderson says. He and his team filmed veiled chameleons (Chamaeleo calyptratus) eating crickets, and controlled the temperature as they watched. For other cold-blooded creatures, the researchers say, an 18-degree Fahrenheit drop in the temperature causes a 33 percent decrease in muscle speed, and an even more dramatic drop-off in the speed of tongue movements. But the chameleons had tongue snaps that only slowed by about 10 to 19 percent … with the same temperature decrease [Scientific American]. The chameleons’ tongues also extended to their full glory despite the temperature change.
Take a good look: according to a new study in PLoS Biology, what you see in this image is a snake about to prey on dinosaur eggs, a 67-million-year-old scene frozen in time and finally discovered. It’s the first time that a snake has been seen eating a dinosaur. The snake is that bit of bones on the left, lead researcher Jeff Wilson says. The egg in the top right contains a tiny titanosaur, one of largest dinosaur groups to ever walk the Earth.
“The snake (Sanajeh indicus) probably lived around the nesting ground and preyed upon hatchlings. They all died instantly when they were covered by a big pulse of sediment from a nearby hill loosened by a storm,” says Wilson [New Scientist]. Wilson guesses that a storm or some other malady might have led the enormous adult dinos to leave the nest, opening the door for the snake to slither in, wait for the baby dinos to hatch, and snack on them. But it never got the chance.
Sure, creatures that reproduce asexually get to avoid some of the hangups that come with sex, but the strategy brings its own problems. First and foremost, how do you prevent genetic deterioration without the fresh infusion of new genes that results from the mixing of male and female DNA? For the all-female whiptail lizard, the solution is to hedge its bets.
In a study forthcoming in Nature, researcher Peter Baumann found that each whiptail lizard egg cells contains twice the number of chromosomes you’d expect. In the fertilized egg cell of a sexually reproducing lizard species, you’d expect to see much what you see in humans—23 chromosomes from the father and 23 from the mother combining into 46. (Most human cells contain 46 chromosomes, but egg and sperm cells contain only 23, so that they can combine to give an offspring a compete, but genetically new, set of chromosomes.)
But the whiptail eggs instead begin with two identical copies of each of their mother’s chromosomes, for a total of 92. Those chromosomes then pair with their identical duplicates, and after two cell divisions, a mature egg with 46 chromosomes is produced. Since crossing-over during the cell divisions occurs only between pairs of identical chromosomes, the lizard that develops from the unfertilized egg is identical to its mother [The New York Times].
Alligators breathe like birds, with a one-way tube that flows all the way through their respiratory systems. While that might not seem earth-shattering at first, alligators and birds diverged 246 million years ago. And according to a new study in Science, that means this breathing technique goes way, way back, and could even explain how the ancestors of dinosaurs survived the great Permian-Triassic extinction.
Unlike a mammal’s breath, which exits the lungs from the same dead-end chambers it enters, a bird’s breath takes a loopy one-way street through its lungs [Science News]. This breathing technique allows birds to explore high altitudes where oxygen levels drop off significantly.
Earlier this month DISCOVER covered the 213-million-year-old fossils of the theropod Tawa hallae, a dinosaur ancestor that could show how early dinos spread around the world. Now, in a study (in press) in the Proceedings of the National Academy of Sciences, another research team has uncovered a surprise in the bones of a theropod from almost 100 million years later. By that time, these creatures may have adopted a clever new weapon: venom.
Sinornithosaurus lived 125 million years ago in what’s now China, and while it might have been covered in feathers (and the size of a turkey), the researchers say it attacked like modern rear-fanged snakes. Rear-fanged snakes don’t inject venom. Instead, the toxin flows down a telltale groove in a fang’s surface and into the bite wound, inducing a state of shock [National Geographic].
Say you’re a goat stuck on a Mediterranean island with scarce food and no way to leave. How do you survive? The strange species Myotragus answered that question by getting small, and, most unusually, adopting the cold-bloodedness normally seen in reptiles.
In a paper in this week’s Proceedings of the National Academy of Sciences, researchers say that the now-extinct dwarf goat managed to survive thousands of years of resource scarcity by adjusting its metabolism to match how much food was available. The discovery marks the first time scientists have seen this cold-blooded survival strategy in mammals. The surprising skill likely allowed the goats to endure potentially fatal periods of scarcity on what is now the Spanish island of Majorca [National Geographic News].
What’s worse than having one gigantic-but-relatively-docile python species invading Florida? Finding out that an extremely aggressive python species is moving in as well, and learning that the two species could theoretically interbreed to create a hybrid monster.
Florida wildlife officials have been concerned for some time about the 20-foot-long Burmese pythons that are thought to have been released by irresponsible pet owners and have established a thriving colony in Everglades National Park. But over the past year, four African rock pythons have also been sighted or captured in Miami-Dade county, giving biologists new cause for concern. Says herpetologist Kenneth Krysko: “They are just mean, vicious snakes…. You couldn’t get a worse python to become established. A Burmese python is just a docile snake. These things will lunge at you” [Miami Herald].