Thursday, 27 April 2017

Limited gene flow between two Bengal tiger populations in the western Himalayan foothills


Connectivity could be maintained by relocating villages, and banning sand and boulder mines 

Date: April 26, 2017
Source: PLOS
 
The flow of genes between Bengal tigers in two reserves of the Terai Arc Landscape in western Himalayan foothills is too low, according to a study published April 26, 2017 in the open-access journal PLOS ONE by Surendra Prakash Goyal from Wildlife Institute of India, India, and colleagues.

Tigers are endangered partly due to habitat loss, which can fragment populations and reduce gene flow among them. Gene flow between populations can maintain genetic variation and spread beneficial gene alleles, so understanding the gene flow of isolated tiger populations i.e. in western Himalayan foothills is crucial in developing management strategies for conserving these big cats. Goyal and colleagues analyzed DNA from 71 samples of tissue, blood or scat from Bengal tigers to assess their gene flow in an 1,800-square-kilometer region of the western Himalayan foothills. The region has two main subpopulations of tigers, one in the Rajaji Tiger Reserve and the other in the Corbett Tiger Reserve.
 

Wednesday, 26 April 2017

This caterpillar could be the key to biodegradable plastic


April 25, 2017

by Chuck Bednar

A species of caterpillar that typically consumes honey and the wax from beehives may be the answer to the growing problem of plastic waste, as new research has revealed that it can easily devour a commonly used type of the material and cause it to return to a useful compound.

As Spanish National Research Council (CSIC) scientist Federica Bertocchini and her colleagues reported Monday in the journal Current Biology, the larvae of the greater wax moth (or Galleria mellonella) is capable of causing polyethylene, a type of plastic used in shopping bags and food packaging, to biodegrade into a substance that can be used in various consumer products. Bertocchini discovered that the caterpillars, which are also known as wax worms, had a taste for plastic while removing them from beehives, Sky News and the Los Angeles Times explained. As she extracted them, she placed them in plastic bags, and later found those bags full of holes.

Following that discovery, she and her colleagues observed wax worms placed on a polyethylene film and found that in as little as 40 minutes, the insects had already started boring holes through the plastic material. In fact, each worm was consuming it at a rate of roughly 2.2 holes/hour, and a team of 100 caterpillars consumed 92 milligrams of a plastic shopping bag in 12 hours.

To further test the wax moth larvae, they created a slurry of worms and placed it on polyethylene films, the Times said. Fourteen hours later, 13 percent of the plastic’s mass had degraded, and the research team discovered that the worms had left behind ethylene glycol – a compound used as a coolant, a heat transfer agent, and in the manufacturing of polyester fibers and plastic bottles.

Continued

Baby whales 'whisper' to mothers to avoid predators: study


April 26, 2017 by Valerie Dekimpe

Newborn humpback whales and their mothers whisper to each other to escape potential predators, scientists reported Wednesday, revealing the existence of a previously unknown survival technique.

"They don't want any unwanted listeners," researcher Simone Videsen, lead author of a study published in Functional Ecology, told AFP.

"Potential predators such as killer whales could listen to their conversations and use that as a cue to locate the calf and predate on it."

Whales are known for their loud calls, congregating fellow members of the pod. Male humpback whales also emit reverberating sounds to attract females during the mating season.

But this is the first time scientists have observed a unique, intimate form of communication between humpback mothers and calves.

Researchers from Denmark and Australia tracked each of eight calves and two mothers for 24 hours in Exmouth Gulf, Western Australia, a breeding ground for Antarctic humpback whales seeking warmer waters to mate and give birth.

Using tags attached to the animals, the team of scientists recorded their faint squeaks and grunts.

"These signals between mother and calf are more quiet than those of normal adult humpback whales," Videsen said, noting they were 40 dB lower than the singing of males in the area.

While a male's cry can resound over an area covering several kilometres, the pairs in the study could only hear each others' calls within a distance of less than 100 metres (330 feet), she added.

Read more at: 

Researchers identify genes that help trout find their way home

April 26, 2017 by Robin A. Smith
 
Scientists have identified genes that enable rainbow trout to use Earth’s magnetic field to find their way back to the streams where they were born. Credit: Eric Engbretson, U.S. Fish and Wildlife Service

In the spring when water temperatures start to rise, rainbow trout that have spent several years at sea traveling hundreds of miles from home manage, without maps or GPS, to find their way back to the rivers and streams where they were born for spawning.

In a study published April 26, 2017 in Biology Letters, researchers have identified genes that enable the fish to perform this extraordinary homing feat with help from Earth's magnetic field.

Generated by the flow of molten metal in its core, the Earth's magnetic field ranges from a mere 25 microteslas near the equator to 65 microteslas toward the poles—making it more than a hundred times weaker than a refrigerator magnet.

Diverse animal species can detect such weak magnetic fields and use them to navigate. First identified in birds in the 1960s, this sense, called magnetoreception, has since been documented in animals ranging from bees and salamanders to sea turtles.

But despite more than half a century of research, the underlying molecular and cellular machinery remains a mystery.

To work out the genetic basis, Duke University postdoctoral associate Bob Fitak and biology professor Sönke Johnsen and colleagues investigated changes in gene expression that take place across the rainbow trout genome when the animal's magnetic sense is disrupted.

In a basement aquarium on the Duke campus, they randomly scooped up one fish at a time from a tank into a small holding container, and placed the container inside a coil of wire. The coil was connected to a capacitor, which discharged an electric current to create a split-second magnetic pulse inside the coil, about 10 times weaker than the magnetic field generated by an MRI machine in a hospital.

Next the researchers sequenced all the gene readouts, or RNA transcripts, present in the brains of 10 treated fish and 10 controls to find out which genes were switched on and off in response to the magnetic pulse.

Read more at: 

When Hunting Pythons, It Helps to Dance Like a Monkey—and Carry a Sledgehammer - via Herp Digest


Florida’s Everglades are crawling with nonnative giant snakes, and authorities have hired an elite corps of hunters to track them down; ‘you juke left, you juke right’

By Arian Campo-Flores, Wall Street Journal, April 21, 2017 

THE EVERGLADES, Fla.—For people who prefer to avoid large, scary snakes, Tom Rahill’s routine won’t be of much use.
 
Anyone desiring to get acquainted with a python deep in the wild, though, would do well to learn his “scalded-monkey dance.”
 
That’s the shimmy Mr. Rahill does when he hunts down a fat Burmese python in the Everglades—a bob-and-weave boogie he uses to avoid the snake’s strikes until he can subdue and grab it.
 
“The attractive thing about this,” he said of snake-hunting, “is it’s very primal.”

There are multiple ways to catch a python, and Mr. Rahill employs a good number of them as a member of an elite squad of hunters the South Florida Water Management District pays to track down these interlopers, which biologists estimate to number in the tens of thousands.

The nonnative serpents have spread through the Everglades, gobbling birds and mammals. They grow as thick as telephone poles and as long as 20 feet. They aren’t venomous, killing by coiling around an animal and suffocating it before gulping. There have been reports abroad of pythons swallowing humans.

“I’m feeling good about this,” said Mr. Rahill one morning last month, trudging through dense brush while swatting mosquitoes and avoiding poisonwoods that can trigger rashes.
Mr. Rahill is the 59-year-old founder of Swamp Apes, a group that takes military veterans into the wilderness for various activities including snake hunting. He said it has bagged more than 400 pythons.

“This is perfect python habitat,” he said, approaching an elevated hardwood hammock. He looked for telltale signs—matted grass, shed skin—jabbing his walking stick into crevices.
He sniffed the air for python poop. “Acrid,” he explained, “more biting than gator” variety.

Mr. Rahill, a telecom administrator, is among 25 hunters the agency selected from more than 1,000 applicants to hunt down the beasts. The elite few include three Swamp Apes members and Dusty “The Wildman” Crum, 36, an orchid grower whose hunting team in a 2016 contest nabbed a 15-foot python.
 
The agency pays $8.10 an hour, $50 per python—must be delivered dead—and $25 for each foot over four.

The program is the latest in a string of attempts by state and federal agencies to eradicate the beasts, from deploying dogs trained to pick up their scent to releasing “Judas snakes” outfitted with radio transmitters to lure other pythons.

In January, the Florida Fish and Wildlife Conservation Commission and other parties hired two members of the snake-hunting Irula tribe in India, who the agency says captured 33 pythons over a two-month period.

They began each day with a sort of prayer and “would ask the powers that be for the vision to see these snakes,” said Joe Wasilewski, 64, a conservation biologist who helped arrange the effort.
 
Then they would light up thin Indian “bidi” cigarettes and head out, searching for faint signs of the serpents. “They’re so darn good at it,” Mr. Wasilewski said. “They’re like exterminators.”

None of the initiatives has done much to curb the Everglades-python population. Though the snakes can reach monstrous proportions, their camouflage and tendency to hide in holes and under leaves make them difficult to spot. “You can stand right on top of it in vegetation,” said Bryan Falk, 38, a U.S. Geological Survey research ecologist, “and you wouldn’t know it.”

Pythons, native to Asia, probably entered the Everglades decades ago when they escaped from, or were released by, people who bought them as pets, scientists say. They eat marsh rabbits and wading birds, robbing native predators such as panthers and alligators.

Bobby Hill, 65, whose job is to remove exotic species from land overseen by the water-management district, said he has found deer hoofs, alligator scales and a bobcat claw in pythons’ bellies. Years ago, along local highways, “you’d see road kill—raccoons, possums,” he said. “You don’t see that too much anymore.”
Hunters say the best time to find pythons is after a cold night when the sun begins to bake the ground where the reptiles head to bask. Most of the year, the steam-bath environment sends them searching for cover.

If a hunter locates one, the challenge is catching it. In dense foliage, Mr. Rahill yanks on the body to pull it toward a clearer spot where it can’t coil around anything. Then he tries to subdue it by the neck.

There are dangers at either end: strikes from its head and defensive sprays from its tail of musk and excrement. “They’ll fling white blobs of poop everywhere,” Mr. Rahill said.
Which is where the scalded-monkey dance comes handy. “You juke left, you juke right” to avoid strikes, he said, until the reptile is tired out and provides an opening to pounce.

Another Swamp Ape, he said, does more of a ballet movement. “He’s a joy to watch, so smooth and fluid.”

Mr. Hill prefers a simpler snake-subjugation tactic: He grabs his Winchester 12-gauge shotgun and fires at the python’s head. “A head shot is considered a humane way” to kill a snake, said Mr. Hill, who said he has been involved in capturing more than 700 pythons.

On the recent day in the Everglades, Mr. Rahill found no snake in the brush, so he tried a method he calls “road cruising.” He hugged the roadside in his black Chevy Cavalier—295,000 miles on the odometer, missing a hubcap—searching through the open window for that python-skin glisten.
He ended the day empty-handed, saying “the key to successful pythoning is perseverance.”

Novice hunters often don’t realize how difficult it is to pursue pythons, he said. “Some people think pythons are waiting on levees with signs saying, ‘Welcome to Florida.’ ”
Days later, farther north, he was tramping through brush and glimpsed a python pattern on a mound, he said. He lunged at it, grabbed at the snake midbody and pulled it into the open. The snake tried to strike him several times before he subdued and bagged it.

The 7-footer yielded a $125 bonus. “I earned that snake,” he said.
The snake earned a swift end dealt by Mr. Rahill’s sledgehammer.
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