Take a trip to a black hole with Stephen Hawking as a guide, watch glowing bioluminescent earthworms wriggle away from predators and discover the fascinating mathematics of origami — all while cuddled up in front of a laptop. That’s the promise of the online streaming service CuriosityStream, which offers hefty doses of science for viewers who prefer fact-based documentaries over reality TV, sports and the political bickering that dominate today’s television programming.
CuriosityStream, which recently celebrated its second birthday, operates much like Netflix. With plans starting at $2.99 per month, users can browse more than 1,700 commercial-free programs covering science, technology, history and the arts. The service works on computers, mobile devices and streaming players such as Roku and Apple TV. CuriosityStream aims to supplement the media diet of science-starved viewers. “When you look at television … there’s very little science on anymore,” says Steve Burns, CuriosityStream’s chief programming officer. Subscribers, he says, “crave the substance that they’ve been missing on TV for so long.”
Along with a slew of documentaries from the BBC and other public broadcasters, CuriosityStream offers more than 600 original programs that you won’t find anywhere else. One standout is David Attenborough’s Light on Earth, in which the naturalist takes viewers on an engaging survey of bioluminescent life, from flickering fireflies and luminous mushrooms to eerily glowing ocean creatures.
Another enjoyable original is Stephen Hawking’s Favorite Places, in which the famed physicist tours a black hole, exoplanet Gliese 832c, Saturn and other cosmic locales. Computer-generated imagery of the turbulent region around a black hole, for example, provides a brilliant visual background to Hawking’s explanations of relevant research. One episode is currently available, and two new ones are slated to go online later in the year.
Some shows are more engaging than others. Another original, The Hunt for Dark Matter, takes a deep dive into the technology behind the search for the invisible substance thought to pervade the universe. But the show will likely fall flat for many viewers, as its introduction lacks some of the background on the physics of dark matter that is necessary to grasp the relevance of the work.
CuriosityStream provides a wealth of options to choose from, including a variety of shorter shows, each 10 or 15 minutes long. With new programs added regularly, the service should provide enough binge-worthy fodder to keep even the most avid documentary lovers busy
Premature babies, who often develop jaundice because of an excess of bile pigment called bilirubin, can be saved from this dangerous condition by the use of fluorescent light.… The light alters the chemistry of bilirubin so it can be excreted with the bile. Exchange transfusion is the usual treatment when jaundice occurs but this drastic procedure carries a … risk of death. —Science News, June 17, 1967
Update Preemies aren’t the only babies at risk for jaundice. About 60 percent of full-term infants also develop the condition. Severe cases can cause brain damage if untreated. But today, some researchers warn that light therapy, now widely used, may not work for babies whose bilirubin levels are very high. And studies have begun to suggest a link between the therapy and certain childhood cancers (SN Online: 1/30/15). Though the risk of developing cancer is small, doctors should be cautious about prescribing the treatment, researchers wrote in 2016 in Pediatrics.
On June 18, 4-year-old Bentley Thomas Koch fatally shot himself in the face. A few weeks earlier, Harmony Warfield, age 7, was shot and killed by her 2-year-old cousin. And teens Shadi Najjar and Artem Ziberov, both on the eve of graduating from high school, died in a hail of gunfire. Stories like these of kids dying from gunshot wounds are devastating, but, sadly, they aren’t an anomaly.
The most comprehensive look at fatal and nonfatal firearm injuries among children in the United States makes that abundantly clear. Every day, roughly 19 children die or are medically treated in an emergency department for gun-inflicted wounds, a study published June 19 in Pediatrics finds.
The statistics, based on data from 2002 to 2014, are stark:
Nearly 1,300 children, from birth to age 17, die from gunshot wounds each year on average and another 5,790 kids are wounded; Of the deaths, 53 percent are homicides, 38 percent are suicides and 6 percent are accidents; Boys ages 13 to 17 make up the bulk of gunshot victims; Cause of death varies by race — African-Americans are overwhelmingly more likely to die from homicide than suicide; white kids are nearly three times as likely to die from suicide as from homicide; and for American Indian and Asian-American kids, it’s 50-50. But this study doesn’t just lay out the numbers. It starts to dig deeper into the whys. And those whys can have important implications, laying the framework for policies that could ultimately lead to a drop in the numbers.
For the numbers, Katherine Fowler, a behavioral scientist at the U.S. Centers for Disease Control and Prevention, and colleagues started with data from the National Vital Statistics System and the National Electronic Injury Surveillance System.
For the whys, her team looked at cases described in the National Violent Death Reporting System, or NVDRS. That let the researchers fill in details like where an incident took place and whether it involved multiple victims — for instance, a homicide followed by suicide or a multiple victim homicide. The database also includes demographic information about the shooter, evidence of alcohol or drugs at the time of death, and whether the incident was gang-related or involved a boyfriend or girlfriend or parents. Clues to whether relationship, financial or school issues were part of the problem also come to light, as does evidence of depression, anxiety, any previous suicide attempt, treatment for mental health problems and physical health problems. Notes about playing with a gun or thinking the gun was a toy, as well as hunting accidents are also included. This tally of circumstances led Fowler and colleagues to conclude that firearm homicides of younger children, up through age 12, often involve conflict between parents, intimate partners or among family. “This highlights how children can be caught in the cross fire in cases of domestic violence and points to the importance of addressing the intersection of these forms of violence,” she says.
The results also reveal something important about child suicides involving guns. “While mental health factors are important, the findings also show that firearm suicides were also frequently related to situational life stressors and relationship problems with an intimate partner, friend or family member,” Fowler notes.
It’s these kinds of details that can help researchers and lawmakers create more effective policies to prevent such tragic deaths and injuries. It’s worked in other cases. Statistics have shown that tweaks to laws regulating the times of day teens can drive lead to injury prevention. Ditto for access to free swimming lessons when it comes to stopping accidental drownings. But similar data on gun deaths and injuries and the effectiveness of policy to prevent them are harder to come by thanks to lack of funding and political support (SN: 5/14/16, p. 16).
Even so, “we know kids are killing themselves and others with guns,” says David Hemenway, a Harvard University economist and an expert in gun research. When it comes to combatting the problem, “the circumstances help narrow down the policy.”
Fowler says the findings “highlight the need for evidence-based solutions to address this public health problem.” She’s armed with a laundry list of potential policies that could have an impact on the whys of gun violence and make a dent in the stats. School counseling programs could help kids manage their emotions and develop skills to resolve problems in relationships and with peers, she says. Along with therapy, those programs could help to reduce suicidal behavior and youth violence. Street outreach programs may also reduce gang-related violence. Parents and pediatricians talking about storing guns safely — a policy touted by the American Academy of Pediatrics, but one that has met resistance in some states — is another option.
There’s another big need, too: more data.
Despite a better picture of what’s happening when kids get a hold of guns, the data are fragmentary and incomplete, says pediatrician Eliot Nelson of the University of Vermont Children’s Hospital in Burlington. For instance, information from the NVDRS was limited to 17 states, so the numbers aren’t nationally representative. Last year, the database was expanded to 42 states and could eventually be expanded to all 50, but that will take additional funding from Congress.
The way gun injury and death data are coded in databases is another issue. Many unintentional deaths, such as when a child accidentally shoots and kills a sibling or friend, are labeled homicides, Hemenway says. Such misclassifications make it more difficult to create a policy, he says. Take, for instance, encouraging parents to lock up guns in the house. Without correctly coded data to say that younger kids are more likely to be killed by a gun at home while older kids are more likely to be killed by guns at a friend’s house, it’s harder to know how to talk to parents. For parents of young kids, the message might be to lock up their own guns; for parents of older kids, it might be to inquire about guns at the homes of their children’s friends. “We don’t always know who best to target our message to,” Nelson says.
Studies such as Fowler’s are slowly filling in the gaps. But not fast enough for kids like Bentley, Harmony, Shadi and Artem. “We want to keep growing our knowledge to prevent problems,” Nelson says. But, he says, it’s hard to do when money and politics hamper research into the problem. Gun-related deaths ranks third as the leading cause of death in 1- to 17-year-olds in the United States. “Gun death in kids is such a common problem,” Nelson says. “We can’t continue to ignore it.”
In Carl Sagan’s 1985 sci-fi novel Contact, a radio astronomer battles naysayers and funding setbacks to persist in her audacious plan — scanning the skies for signals from aliens. Sagan had real-life inspiration for his book (and the 1997 movie of the same name): astronomer Jill Tarter, who spearheaded the search for extraterrestrial intelligence, or SETI, for decades.
In Sagan’s story, the protagonist, Ellie Arroway, detects mysterious chatter from the cosmos. Tarter had no such luck. But her story, told by journalist Sarah Scoles in Making Contact, still provides insights into what it means to be human in a vast universe potentially harboring other life. Tarter began her career as a typical radio astronomer, studying mainstream topics like stars and galaxies as a Ph.D. student. But after graduating in 1975, she began to focus on SETI, poring over data from radio telescopes, searching for unnatural blips that could be a sign of an intelligent civilization. SETI researchers typically focus on radio waves because those long wavelengths can travel through our galaxy’s dust without being absorbed. Writings about SETI are prone to dreamy romanticism, but Making Contact admirably steers clear of excessive sentimentality. As a child gaping at the stars, Tarter wondered if creatures in the heavens were looking in our direction. Of course, Scoles notes, plenty of kids have wondered the same thing. Though Tarter’s childhood musings might seem special in retrospect, they aren’t what make her stand out.
Instead, Scoles — who has clear affection for her subject — highlights Tarter’s tenacity. In the face of numerous obstacles, Tarter pushed the field forward, seemingly by force of will.
In a detailed portrait of how the science sausage gets made, the book follows Tarter as she faced numerous funding woes. The field of SETI, which has at various points in its history received money through NASA, is an easy target for funding cuts, with some politicians deriding it as a wasteful hunt for “little green men.” Tarter, like the fictional Arroway, fought with Congress for taxpayer dollars SETI received, then scrambled for cash from other sources to keep telescopes and other equipment in operation. Wealthy donors kept SETI afloat — and still do. To maximize their ability to accept funding, Tarter and other SETI pioneers founded the nonprofit SETI Institute, in Mountain View, Calif., in 1984. Throughout, Tarter somehow managed to maintain her passion for a long shot search.
Although it’s a compelling story, the book stumbles in a few places, mainly minor sloppiness with physics facts, which may bother the most astute readers. (Scoles writes, for example, “Light is the only way we can learn about the universe,” neglecting gravitational waves and neutrinos, both of which have revealed secrets of cosmic objects.)
Now retired, Tarter has lost her chance to follow in Arroway’s fictional footsteps — she will never find any alien communiqués. But even if astronomers never hear from E.T., Tarter sees benefits in the search: SETI is an opportunity to make humankind less selfish. Just the thought that other creatures might inhabit the universe can make human squabbles seem less significant.
A strange property of spider silk helps explain how the arachnids avoid twirling wildly at the end of their ropes.
Researchers from China and England harvested silk from two species of golden orb weaver spiders, Nephila edulis and Nephila pilipes, and tested it with a torsion pendulum. The device has a hanging weight that rotates clockwise or counterclockwise, twisting whatever fiber it hangs from. When a typical fiber is twisted, the weight spins back and forth around an equilibrium point, eventually returning to its original orientation. But unlike several fibers the scientists tested — copper wires, carbon fibers and even human hair — the spider silk deformed when twisted. That distortion changed the silk’s equilibrium point and cut down on the back-and-forth spinning, the scientists report in the July 3 Applied Physics Letters. Eventually, scientists might design spin-resistant ropes for mountain climbers, who, like spiders, should avoid doing the twist.
A new type of soft robot can go under the knife and make a full recovery in about a day.
Researchers fashioned a robotic hand, gripper and muscle from self-healing rubbery material. To test their robots’ resilience, the engineers sliced each with a scalpel, then put them in an oven. After cranking up the heat to 80° Celsius, baking the bots for 40 minutes, then cooling them to room temperature, the researchers found that all three bots’ cuts had completely closed up. Twenty-four hours later, the machines had regained at least 98 percent of their original strength and flexibility, the researchers report online August 16 in Science Robotics. Incisions broke bonds between two chemical ingredients that make up the material, furan and maleimide. At higher temperatures, these chemical compounds can also split up, as well as move around more easily. So as the researchers cooled the material, the compounds were able to re-bond with those on the other side of an incision. “This material could heal, in theory, an infinite number of times,” says study coauthor Bram Vanderborght, an engineer at Vrije University Brussels.
The work helps address a major limitation of squishy, flexible robots — which are better suited than their traditional, rigid counterparts for navigating rough terrain and handling fragile objects, but are vulnerable to punctures and tears. Self-healing machines could pave the way for creating more durable, reusable soft bots.
Three days after Bronny James revealed that he had committed to USC, the Trojans have landed another son of an NBA great.
DJ Rodman, the son of five-time NBA champion Dennis Rodman, announced on Tuesday that he will transfer to USC for the 2023-24 season.
Rodman played four seasons at Washington State. He will use his extra year of eligibility to join a USC team that is loading up on talent.
Just how good is Rodman? And what role could he play for the Trojans?
How good is DJ Rodman? Rodman was a reliable starter in 30 out of 31 games for Washington State this past season. He is coming off his most impactful year, posting 9.6 points, 5.8 rebounds, 1.4 assists and 0.7 steals while shooting 38.1 percent from beyond the arc in 2022-23.
Rodman scored in double figures in 12 contests this past year, including a 23-point performance against Eastern Washington in the NIT. He corralled double-digit rebounds in four games and snagged at least two steals in eight games.
Rodman plays on the wing, but he competes on the defensive end and on the glass — just like his father. He's a versatile defender who will take on perimeter assignments and battle big men in the post.
He'll create second-chance opportunities with a nose for the ball as an offensive rebounder, and he's capable of stretching the floor with an improved 3-point shot.
Rodman will add depth to a reloaded USC roster that should compete for a Pac-12 championship next season.
DJ Rodman college stats Rodman played 111 games over four seasons at Washington State. He served as a role player over his first three seasons before being promoted to the starting lineup for his senior season.
You can find his career averages below:
21.7 minutes per game 5.5 points per game 4.0 rebounds per game 0.9 assists per game 0.4 steals per game 0.2 blocks per game 39.8 percent FG 35.2 percent 3PT 77.6 percent FT USC roster for 2023, including DJ Rodman and Bronny James Name Height Position Class Hometown High School Isaiah Collier 6-4 G FR Marietta, Ga. Wheeler HS Bronny James 6-3 G FR Los Angeles, Calif. Sierra Canyon HS Arrinten Page 6-9 F FR Marrieta, Ga. Wheeler HS Kobe Johnson 6-6 F JR Milwaukee, Wis. Nicolet HS Vincent Iwuchukwu 7-1 F SO San Antonio, Texas Southern Calif. Academy Oziyah Sellers 6-5 G SO Hayward, Calif. Southern Calif. Academy Boogie Ellis 6-3 G SR San Diego, Calif. Mission Bay HS Zach Brooker 6-0 G SR Calabasas, Calif. Sierra Canyon HS Joshua Morgan 6-11 F SR Sacramento, Calif. Sheldon HS Harrison Hornery 6-10 F JR Toowoomba, Australia Mater Dei HS Kijani Wright 6-9 F SO Los Angeles, Calif. Sierra Canyon HS DJ Rodman 6-6 F SR Newport Beach, Calif. JSerra Catholic HS Did LeBron James and Dennis Rodman play together? No, they did not.
Rodman retired after the 1999-00 season. James was drafted in 2003, making his NBA debut at the start of the 2003-04 season.
The 28-year-old space telescope, in orbit around the Earth, put itself to sleep on October 5 because of an undiagnosed problem with one of its steering wheels. But once more, astronomers are optimistic about Hubble’s chances of recovery. After all, it’s just the latest nail-biting moment in the history of a telescope that has defied all life-expectancy predictions.
There is one major difference this time. Hubble was designed to be repaired by astronauts on the space shuttle. Each time the telescope broke previously, a shuttle mission fixed it. “That we can’t do anymore, because there ain’t no shuttle,” says astronomer Helmut Jenkner of the Space Telescope Science Institute in Baltimore, who is Hubble’s deputy mission head. The most recent problem started when one of the three gyroscopes that control where the telescope points failed. That wasn’t surprising, says Hubble senior project scientist Jennifer Wiseman of NASA’s Goddard Space Flight Center in Greenbelt, Md. That particular gyroscope had been glitching for about a year. But when the team turned on a backup gyroscope, it didn’t function properly either.
Astronomers are working to figure out what went wrong and how to fix it from the ground. The mood is upbeat, Wiseman says. But even if the gyroscope doesn’t come back online, there are ways to point Hubble and continue observing with as few as one gyroscope.
“This is not a catastrophic failure, but it is a sign of mortality,” says astronomer Robert Kirshner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Like cataracts, he says, it’s “a sign of aging, but there’s a very good remedy.” While we wait for news of how Hubble is faring, here’s a look back at some of its previous hiccups and repair missions.
1990: The blurry mirror On June 27, 1990, three months after the space telescope launched, astronomers discovered an aberration in Hubble’s primary mirror. Its curvature was off by two micrometers, making the images slightly blurry.
The telescope soldiered on, despite being the butt of jokes on late-night TV. It observed a supernova that exploded in 1987 (SN: 2/18/17, p. 20), measured the distance to a satellite galaxy of the Milky Way and took its first look at Jupiter before the space shuttle Endeavour arrived to fix the mirror in December 1993. 1999: The first gyroscope crisis On November 13, 1999, Hubble was put into safe mode after the fourth of its six gyroscopes failed, leaving it without the three working gyros necessary to point precisely. An already planned preventative maintenance shuttle mission suddenly became more urgent. NASA split the mission into two parts to get to the telescope more quickly. The first part became a rescue mission: Astronauts flew the space shuttle Discovery to Hubble that December to install all new gyroscopes and a new computer.
2004: Final shuttle mission canceled After the space shuttle Columbia disintegrated while re-entering Earth’s atmosphere in 2003, NASA canceled the planned fifth and final Hubble reservicing mission. “That could really have been the beginning of the end,” Jenkner says.
The team has known for more than a decade that someday Hubble will have to work with fewer than three gyroscopes. To prepare, Hubble’s operations team deliberately shut down one of the telescope’s gyroscopes in 2005, to observe with only two.
“We’ve been thinking about this possibility for many years,” Wiseman says. “This time will come at some point in Hubble’s mission, either now or later.”
Shutting down the third gyroscope was expected to extend Hubble’s life by only eight months, until mid-2008. In the meantime, two of the telescope’s scientific instruments — the Space Telescope Imaging Spectrograph and the Advanced Camera for Surveys — stopped working due to power supply failures. 2009: New lease on life Fortunately, NASA restored the final servicing mission, and the space shuttle Atlantis visited Hubble in May 2009 (SN Online: 5/11/09). That mission restored Hubble’s cameras, installed new ones and crucially, left the space telescope with six new gyroscopes, three for immediate use and three backups. The three gyroscopes still in operation (including the backup that is currently malfunctioning) are of a newer type, and are expected to live five times as long as the older ones, which last four to six years.
The team expects Hubble to continue doing science well into the 2020s and to have years of overlap with its successor, the James Webb Space Telescope, due to launch in 2021. “We are always worried,” says Jenkner, who has been working on Hubble since 1983. “At the same time, we are confident that we will be running for quite some time more.”
We may truly be led by our noses. A sense of smell and a sense of navigation are linked in our brains, scientists propose.
Neuroscientist Louisa Dahmani and colleagues asked 57 young people to navigate through a virtual town on a computer screen before being tested on how well they could get from one spot to another. The same young people’s smelling abilities were also scrutinized. After a sniff of one of 40 odor-infused felt-tip pens, participants were shown four words on a screen and asked to choose the one that matched the smell. On these two seemingly different tasks, the superior smellers and the superior navigators turned out to be one and the same, the team found.
Scientists linked both skills to certain spots in the brain: The left orbitofrontal cortex and the right hippocampus were both bigger in the better smellers and better navigators. While the orbitofrontal cortex has been tied to smelling, the hippocampus is known to be involved in both smelling and navigation. A separate group of nine people who had damaged orbitofrontal cortices had more trouble with navigation and smell identification, the researchers report October 16 in Nature Communications. Dahmani, who’s now at Harvard University, did the work while she was at McGill University in Montreal.
A sense of smell may have evolved to help people find their way around, an idea called the olfactory spatial hypothesis. More specific aspects of smell, such as how good people are at detecting faint whiffs, could also be tied to navigation, the researchers suggest.
In a broad swath of northwestern Alaska, small groups of recent immigrants are hard at work. Like many residents of this remote area, they’re living off the land. But these industrious foreigners are neither prospecting for gold nor trapping animals for their pelts. In fact, their own luxurious fur was once a hot commodity. Say hello to Castor canadensis, the American beaver.
Much like humans, beavers can have an oversized effect on the landscape (SN: 8/4/18, p. 28). People who live near beaver habitat complain of downed trees and flooded land. But in areas populated mostly by critters, the effects can be positive. Beaver dams broaden and deepen small streams, forming new ponds and warming up local waters. Those beaver-built enhancements create or expand habitats hospitable to many other species — one of the main reasons that researchers refer to beavers as ecosystem engineers. Beavers’ tireless toils — to erect lodges that provide a measure of security against land-based predators and to build a larder of limbs, bark and other vegetation to tide them over until spring thaw — benefit the wildlife community.
A couple of decades ago, the dam-building rodents were hard to find in northwestern Alaska. “There’s a lot of beaver around here now, a lot of lodges and dams,” says Robert Kirk, a long-time resident of Noatak, Alaska — ground zero for much of the recent beaver expansion. His village of less than 600 people is the only human population center in the Noatak River watershed. Beavers may be infiltrating the region for the first time in recent history as climate change makes conditions more hospitable, says Ken Tape, an ecologist at the University of Alaska Fairbanks. Or maybe the expansion is a rebound after trapping reduced beaver numbers to imperceptible levels in the early 1900s, he says. Nobody knows for sure. And the full range of changes the rodents are generating in their new Arctic ecosystems hasn’t been studied in detail. But from what Tape and a few other researchers can tell so far, the effects could be profound, and most of them will probably be beneficial for other species.
In the areas newly colonized by beavers, “some really interesting processes are unfolding,” says John Benson, a wildlife ecologist at the University of Nebraska–Lincoln who studies wolves and coyotes, among other beaver predators. “I’d expect some pretty dramatic changes to the areas they take over.”
Beavers’ biggest effects on Arctic ecosystems may come from the added biodiversity within the ponds they create, says James Roth, an ecologist at the University of Manitoba in Winnipeg, Canada. These “oases on the tundra” will not only provide permanent habitat for fish and amphibians, they’ll serve as seasonal stopover spots for migratory waterfowl. Physical changes to the environment could be just as dramatic, thawing permafrost decades faster than climate change alone would.
The Arctic tundra isn’t the first place beavers have made their mark. Changes seen in beaver-rich areas at lower latitudes may offer some clues to the future of the Alaskan tundra, home to moose, caribou and snowshoe hares.
North through Alaska As Earth’s climate has warmed in recent years, some plants and animals — such as the mountain-dwelling pika, a small mammal related to rabbits — have fled the heat by moving to higher altitudes (SN: 6/30/12, p. 16). Others, from moose and snowshoe hares to bull sharks and bottlenosed dolphins, have moved toward the poles to take advantage of newly hospitable ecosystems (SN: 5/26/18, p. 9).
Arctic environments have changed more than most, Tape says. Polar regions are warming much faster than other parts of the world, he says. Studies estimate that average temperatures in the Arctic have risen about 1.8 degrees Celsius since 1900, about 60 percent faster than the Northern Hemisphere as a whole.
This warming is bringing great change to the Alaskan tundra, Tape says. Winter snow cover doesn’t persist as long as it used to. Streams freeze later in the fall and melt earlier in the spring. Permafrost, the perennially frozen ground, is thawing, allowing shrubs to take hold. New species are moving in, few more noticeable than the beaver. The dams they build and the ponds they create are hard to miss; these newly formed bodies of water even show up on satellite images. Beavers have infiltrated three watersheds in northwestern Alaska in the last couple of decades. Together these drainages cover more than 18,000 square kilometers — an area larger than Connecticut.
On images of the region collected by Landsat satellites in summer months from 1999 through 2014, Tape and colleagues looked for new areas of wetness that covered at least half a hectare (1.24 acres), or about four times the area covered by an Olympic swimming pool.
The researchers then used newer, high-resolution satellite images to verify the presence of beaver ponds. Available aerial photographs taken before 1999 didn’t pick up any signs of beaver activity in the area, Tape says. Kirk notes that beavers were present in the Lower Noatak River watershed before 1999, but in vastly smaller numbers than they are today.
Based on the images at hand, the researchers found 56 new complexes of beaver ponds in the area over the 16-year study period. On average, beavers expanded their range about 8 kilometers per year, Tape and colleagues reported in the October Global Change Biology.
“This is remarkable, but it shouldn’t come as a surprise,” Tape says. “Beavers are engineers that work every day, all summer long.”
The animals have also made their way into western Alaska’s Seward Peninsula and the northern foothills of the Brooks Range, mountains that stretch east to west across northern Alaska, the researchers found. If the animals’ recent rate of expansion continues, beavers could spread throughout Alaska’s North Slope in the next 20 to 40 years, the researchers say. The Lower Noatak River watershed, one of the areas that Tape and colleagues studied, is mostly tundra. By definition that means treeless plain. But the area also is about 3.5 percent forest, mainly concentrated along the river and its tributaries. The watersheds just to the north are completely tundra. So how do the beavers there build dams without trees? In those areas, Tape says, the animals construct smaller dams than they might at lower latitudes, using the branches, twigs and foliage of willows and other shrubs.
“I never expected to see beavers on the tundra,” Roth says, intrigued by Tape’s team’s findings.
Happy place The beavers are not only persisting on the tundra, they’re thriving. The moderately sized streams and flat terrain provide ideal habitat. And once they gain a foothold, these industrious creatures set about making improvements that are probably an overall plus for myriad other species, Tape says.
For instance, frigid conditions in the region cause shallow streams to freeze solid in winter. But when a beaver builds a dam, the water that gathers upstream of the structure becomes deep enough to remain liquid below a sheet of ice that provides insulation from the chilly winter air.
That persistent liquid lets the beavers move about under the ice even in the depths of winter. The water gives them a place to stockpile food, too, Tape notes. That constant supply of liquid water also provides year-round habitat for fish, amphibians and even some insects in their larval stages. None of these species are part of the beaver’s diet, but they could serve as food for other creatures. “All that diversity would add whole new layers to food webs,” Roth says. Ecological changes could extend well beyond the beaver pond. The water impounded by beaver dams sometimes finds its way past the dam, Tape says. The satellite photos that he and his colleagues analyzed revealed that some stretches of river just downstream of beaver dams now remain unfrozen even in winter. That flowing water probably spills over the dam or around its edges, but some may seep through or under the structure.
That liquid water also helps thaw the underlying permafrost. Previous studies have shown that even a shallow pond less than a meter deep can boost sediment temperature by as much as 10 degrees C above the locale’s average air temperature. That kind of warming causes permafrost to thaw decades earlier than it would without the pond. Although scientists are concerned that permafrost thawing will release stored carbon into the atmosphere, no one yet knows how that thawing will affect the balance of carbon emissions to the atmosphere (SN: 1/21/17, p. 15).
Field studies at lower latitudes hint that beavers will probably bring about other ecological changes, too, Tape says, which might shift over time. For example, moose and snowshoe hares eat the same willow shrubs that beavers consume and build their dams with. And ptarmigan, a crow-sized bird in the grouse family, rely on those shrubs for cover, especially during winter. So immediately after beavers move into an area and start clearing that brush, populations of those species may decline.
But the long-term benefits will probably outweigh the short-term impacts on those species, says Matthew Mumma, an ecologist at the University of Northern British Columbia in Prince George, Canada. Permafrost that thaws along the fringe of a beaver pond will probably boost numbers of the shrubs that these species depend on, Tape and colleagues suggest. So in the long run, the overall numbers of moose, hares and ptarmigan may rise. Likewise, Mumma notes, beavers could provide big benefits for salmon and other migratory fish. Beaver dams were once thought to impede the travel of such fish upstream or to reduce the number of places where fish could spawn. But studies in the western United States, among other places, have suggested that the presence of beavers actually helps boost populations of salmon. For instance, the aquatic grasses in beaver ponds offer hiding places for young fish. Also, the languid ponds provide a resting spot for adult fish migrating upstream to spawning sites.
Better-fed wolves Boosting herbivore populations on the tundra would be a boon for local predators, of course. Larger numbers of snowshoe hares, for example, could feed the populations of the arctic foxes that prey upon them, Mumma says. And more moose could mean better-fed wolves.
Beavers themselves make a meal for bears, wolverines and wolves. In areas where wolves and beavers coexist, the rodents make up as much as 30 percent of the wolf diet, Roth says. The presence of a more reliable and more diversified food supply could lead wolves to settle down in smaller territories rather than migrating widely.
Benson and his team have already seen the impact of beaver populations on wolves, coyotes and wolf-coyote hybrids in Ontario’s Algonquin Provincial Park from August 2002 until April 2011.
In that time, 37 of the 105 pups that had been tagged with radio transmitters died, Benson says. The second-highest cause of death was starvation. Every one of those starvation-related deaths took place in the western portion of the park, which has relatively rugged terrain and few beavers. In the eastern portion of the park, where beavers are plentiful, none of the pups starved, Benson and his team reported in 2013 in Biological Conservation. In a separate study, Mumma and colleagues analyzed aerial surveys of beaver populations within seven broad regions in northeastern British Columbia in 2011 and 2012. Proximity to human activity, such as roadbuilding or oil and gas exploration, didn’t seem to affect beavers’ decisions to build at a particular locale. Nor did the presence of wolves in the area, the researchers reported in February in the Canadian Journal of Zoology.
Although having wolves nearby seemed to affect the number of beavers present (quite possibly via consumption), the predators didn’t seem to scare the rodents away entirely, Mumma notes.
More beavers, fewer sick moose Whether the presence of beavers on the Alaskan tundra ends up boosting the numbers of moose and other ungulates, the dam builders could have a big, though indirect, impact on the hoofed browsers’ health.
Roth and parasitologist Olwyn Friesen, now at the University of Otago in Dunedin, New Zealand, recently studied how a wolf’s diet affects the parasites it carries — which can then be passed on to other creatures in the environment. The researchers analyzed 32 wolf carcasses collected by provincial conservation officers in southeastern Manitoba in 2011 and 2012. Those remains came from hunters, trappers and roadkill.
In particular, the team tallied the parasites in the wolves’ lungs, liver, heart and intestines. The group also measured the ratio of carbon-12 and carbon-13 isotopes in the wolf tissues, which provided insight into what sorts of prey each individual wolf had eaten near the time those tissues formed.
Typical prey for wolves in this area are, from most consumed to least: white-tailed deer, snowshoe hare, moose, beaver and caribou, Roth says. Each of these creatures has a distinct ratio of the two carbon isotopes in its tissues. That ratio gets passed along to the predators that eat them.
The wolves with diets heavier in beaver had, on average, fewer intestinal parasites called cestodes. (Tapeworms are the best-known members of that group.)
The implications are clear, Roth and Friesen reported in 2016 in the Journal of Animal Ecology. Beaver-eating wolves are much less likely to excrete parasites into the environment where they could be picked up by ungulates, such as moose and caribou. Wolves don’t seem to be detrimentally affected by such parasites. But ungulates that become infected — especially older animals — may have reduced lung capacity, making escape from predators more difficult. A new resource Although beavers may speed changes in the Arctic, those effects may still take a long time to manifest.
Despite the proliferation of beavers in the Lower Noatak River watershed in the last couple of decades, “things around here grow so slowly, they’re not really having a long-term impact yet,” says local resident Kirk. Shrubs haven’t yet noticeably spread into any areas of permafrost that have been thawed by waters impounded by recent dam-building.
Nor have the beavers made much of a mark on the local economy, he says. “There’s a lot of people harvesting them now, since there’s so many of them around,” he adds. However, the pelts from those rodents are so far used by the trappers themselves, not sold to others.
The beavers haven’t become a big draw on the local food scene, either. Even connoisseurs say the meat has a gamey, greasy taste. As Kirk puts it, “we haven’t adjusted our taste buds to them yet.”
