News and notes: Arctic foxes, drones spying on caribou and what makes hair curly.
THESE ARCTIC FOXES TURNED BLUE. THAT’S A GOOD THING.
Arctic foxes are endangered in Sweden, Norway and Finland, scattered in isolated populations that can fall victim to severe inbreeding, further threatening their survival.
That’s what happened to a group descended from six white foxes that settled in the early 2000s on Helagsfjället, the highest mountain in southern Sweden.
But in 2010, a local ranger noticed something different: slate-colored or “blue” arctic foxes, which had to be newcomers. The immigrants presented a rare opportunity for scientists to study what happens when new genetic material flows into a small, isolated population threatened with extinction.
In a study published recently in Proceedings of the Royal Society B, scientists from Sweden and Norway reported that just three new males dramatically reduced inbreeding and produced a generation of more robust offspring in the Helagsfjället arctic fox population.
The findings lend support to a disputed conservation strategy called genetic rescue, which involves introducing genetic diversity to boost the survival chances of small, inbred populations, said Jennifer Neuwald, an assistant professor of biology at Colorado State University who was not involved in the new study.
“This study showed that having those new individuals bring in new DNA actually had an effect,” she said.
Arctic foxes come in two color morphs. White morphs are snowy in winter and brown-gray in summer, while blue morphs stay a ravishing indigo, brown and charcoal mix year-round.
The blue foxes that arrived in Helagsfjället had come from a captive breeding and restoration program funded by the Norwegian government. In 2009, the program released two blue brothers and another, unrelated white male in southern Norway. The three migrated about 150 miles to the Swedish subpopulation.
Malin Hasselgren, a Ph.D. student in zoology at Stockholm University, led efforts to construct a giant family tree with DNA sampled from 543 foxes, or 105 litters, born in Helagsfjället between 2000 and 2015.
In the five years following the arrival of the new males, the population of the Helagsfjället clan nearly doubled.
Perhaps more important, the first generation of pups born to immigrant fathers was more evolutionarily fit than inbred pups: The former were almost twice as likely to survive their first year of life, and had higher breeding success.
A larger concern is that the benefits of genetic rescue will be short-lived.
Adding new individuals to a threatened population can also introduce disease or swamp local adaptations. Steph Yin
HOW TO SPOT A NUCLEAR BOMB PROGRAM? LOOK FOR GHOSTLY PARTICLES
What are nations like North Korea and Iran really doing at nuclear reactors that are out of sight?
Someday, wispy subatomic particles known as antineutrinos could provide a clear view of what countries with illicit nuclear weapons programs are trying to hide.
Antineutrinos are devilishly difficult to detect, but this quality is precisely what makes them potentially ideal for monitoring international nonproliferation agreements aimed at preventing the spread of atomic weapons.
A collaboration of U.S. and British scientists announced recently that they would build a test antineutrino detector called Watchman in a mine on the northeast coast of England. The project is sponsored by the National Nuclear Security Administration, part of the U.S. Department of Energy.
When completed in 2023, the apparatus is to consist of a cylinder about 50 feet in diameter and 50 feet in height, filled with 7.7 million pounds of water and located about 3,600 feet underground in the Boulby Mine, which produces salt and potash, a fertilizer. Sensors lining the inside of the cylinder will observe the occasional flashes generated when an antineutrino resulting from reactions in the Hartlepool nuclear power plant, about 15 miles away, slams into a particle in the detector liquid. The experiment would run for two years.
“It’s a demonstration of a capability,” said Adam Bernstein, a physicist at Lawrence Livermore National Laboratory in California who is the principal investigator for the project. “Once we’ve operated, then that would give one confidence that you could use this technology for actual monitoring.”
Bernstein said the United States will contribute $30 million over six years to the project.
Neutrinos, particles with no electrical charge and little mass that travel at close to the speed of light, are generated by nuclear fusion, as in the sun, where hydrogen atoms merge into helium, releasing heat and light. Antineutrinos are the antimatter version of neutrinos and are created when atoms fall apart in fission reactions like the decay of uranium. The fission of uranium also produces plutonium, which can be used in nuclear weapons.
— Kenneth Chang
EARLIEST KNOWN HUMAN FOOTPRINTS IN NORTH AMERICA FOUND ON CANADIAN ISLAND
Big feet. Little feet. A heel here. A toe there.
Stamped across the shoreline of Calvert Island, British Columbia, are 13,000-year-old human footprints that archaeologists believe to be the earliest found in North America.
The finding, which was published recently in the journal PLOS One, adds support to the idea that some ancient humans from Asia ventured into North America by hugging the Pacific coastline, rather than by traveling through the interior.
“This provides evidence that people were inhabiting the region at the end of the last ice age,” said Duncan McLaren, an anthropologist at the Hakai Institute and University of Victoria in British Columbia and lead author of the study. “It is possible that the coast was one of the means by which people entered the Americas at that time.”
McLaren and his colleagues
stumbled upon the footprints while digging for sediments beneath Calvert Island’s beach sands. Today, the area is covered with thick bogs and dense forests that the team, which included representatives from the Heiltsuk First Nation and Wuikinuxv First Nation, could only access by boat.
At the close of the last ice age, from 11,000 to 14,000 years ago, the sea level was 6 to 10 feet lower. The footprints were most likely left in an area that was just above the high tide line.
“As this island would only have been accessible by watercraft 13,000 years ago,” McLaren said, “it implies that the people who left the footprints were seafarers who used boats to get around, gather and hunt for food and live and explore the islands.”
The researchers think that after the people left their footprints on the clay, their impressions were filled in by sand, thick gravel and then another layer of clay, which may have preserved them.
Using radiocarbon dating on sediment from the base of some footprint impressions, as well as two pieces of preserved wood found in the first footprint, McLaren and his team found them to be 13,000 years old.
— Nicholas St. Fleur
DRONES SPY CARIBOU ON A TREACHEROUS, ICY CROSSING
Every autumn, caribou gather along the shores of Victoria Island in the Canadian Arctic and wait.
Once the temperature drops and the ice gets thick enough, dozens of them cross together to mainland Canada. There, if they make it, they will spend the winter breeding before heading back to give birth and raise their young on the island.
The Inuit, who share an intimate connection with these caribou, have always said that a few lead and the rest follow along this treacherous Arctic journey. Now, new technology is confirming this centuries-old indigenous wisdom.
In November 2015, scientists led by Andrew Berdahl at the Santa Fe Institute in New Mexico and Colin Torney at the University of Glasgow in Scotland deployed drones to film this migration. With computer vision they analyzed the footage, identifying every individual and tracking their assorted behaviors as they moved together. They found that indeed, caribou paid close attention to the directional cues of their neighbors ahead of them. And despite earlier research models suggesting individuals in migrating groups all act the same, the researchers confirmed what the Inuit knew — some caribou led, while others followed along.
The results, published recently in Philosophical Transactions of the Royal Society B, may help inform conservation efforts for island caribou, which face other pressures that have been exacerbated by warming temperatures and increased ship traffic along their icy migratory routes.
Dolphin and Union caribou, as this endangered population is called, provide an interesting case study because they’re different from other caribou. They’re less social — except during this sea ice migration.
Drone videos offer a more complete view of the varying behaviors of migrating caribou.
The researchers in this study were able to observe how sex or age influenced interactions while traveling, looking at who stayed close to whom and which animals started movements and which copied. They discovered, for example, that calves rely on social cues and stay close to others, but mature bulls were more autonomous.
Berdahl thinks that when these caribou come together, they can better sense and respond to the perilous ice they cross. It’s called collective sensing.
Joanna Klein
WHAT MAKES SOME HAIR CURLY?
Every day is a curly hair day for sheep. Those curls and kinks are part of what makes woolen sweaters so cozy — the maze of fibers helps trap warm air, keeping it close to the body. But wrapped up in those curls may also be answers to a long-standing mystery: exactly how a strand of hair winds itself into a curl on the cellular level.
For many years, there were two competing theories to explain what makes hairs curl in sheep. Research by scientists in New Zealand and Japan published recently in the Journal of Experimental Biology finds that neither theory is exactly correct. But it remains likely that differences between certain cells on a hair may explain what makes a sheep’s wool curly. And while human hair has some crucial differences from wool, understanding why curls happen in one mammal’s hair could eventually shed light on others, including ours.
At first, the cells that will make up a strand of hair are soft and squishy, like little round bags of fluid. But as they grow longer and get extruded through a hair follicle, they get thinner, harder and full of keratin, a protein.
Researchers led by Duane Harland, a scientist at AgResearch in New Zealand, clipped samples from six New Zealand merino sheep.
They were testing two ideas about curliness. The first theory is that as a curling strand is constructed, the cells on one side divide more quickly than those on the other. This would generate a curve in the direction of the side with fewer cells. The other involves the differences between the two types of cells that make up wool fibers: orthocortical cells, which tend to be longer, and paracortical cells, which are shorter. In this theory, a certain proportion of longer cells to shorter cells, arranged on either side of the strand, generates a curl.
They found that there are not fewer cells on the inside of a curve than on the outside, which countered the first theory.
But when they tested the second theory, they found that simply knowing the ratio of long cells to short ones did not allow them to precisely predict a fiber’s curl.
What they did find was that in any given strand, any orthocortical cell will always be longer than any paracortical. That reinforces the idea that the differences between them are linked to the curl.
— Veronique Greenwood