Human beings take up a lot of real estate — around 50-70 percent of the Earth’s land surface. And our increasing footprint affects how mammals of all sizes, from all over the planet, move.
Mammals living in human-modified habitats move two to three times less far than their counterparts in areas untouched by humans. What’s more, this pattern persists globally: from African forest elephants to white-tailed antelope squirrels in North America, the human footprint infringes upon the footprints of mammal species both big and small. The study, led by Marlee Tucker of the Senckenberg Biodiversity and Climate Research Centre in Germany, is the first of its kind to log movement behaviors for such a wide range of mammals globally.
“All organisms need space,” Bruce Patterson, a co-author of this study and MacArthur Curator of Mammals at The Field Museum in Chicago, explained. “They need space to gather their resources, find mates, and perform their ecological services.” For instance, bats need room to find and consume insects and pollinate plants (which amount to $3.5 to 50 billion worth of agricultural labor annually in the US alone), and apex predators need room to hunt and control other species’ populations.
In the study, more than 100 researchers contributed information on 803 individual mammals representing 57 species in total. Patterson offered up data on the movement of lions in a pristine wilderness area of Tsavo, Kenya. From 2002-09, he followed three lions using high-tech collars that continuously tracked individuals’ movement via GPS — the data he contributed to the Science study. One of those lions, in its natural habitat, patrolled an area twice the size of Chicago (1400 km2) to find food, attract mates, and repel intruders.
But habitat loss and fragmentation disrupt these critical animal behaviors. Clearing rainforest is an example of habitat loss — the destruction and loss of usable area for a given species. Constructing a road through the savannah, on the other hand, constitutes habitat fragmentation — the division of habitat area into smaller, discontinuous spaces. When suitable habitat spaces become too small or too isolated, animals can no longer afford to visit them, changing their space use.
As habitats become compromised, resources like food and living space that animals rely on become scarce. Sometimes, when resources are limited, animals traverse larger areas to get what they need — if there’s not enough food in a five-mile radius, they might move to a ten-mile radius. However, this study shows that on the whole, that sort of additional movement tends not to be an option — if there’s no uninterrupted landscape available, then the affected animals simply can’t live there.
To that end, strong negative effects of the human footprint on median and long-distance displacements of terrestrial mammals.” Patterson put it more simply: “Human dominion over Earth’s landscapes gets in the way of animals doing their thing.” Some species, like mice, can make do with less room, but animals that need lots of space, like lions, tigers, and elephants, simply can’t live in areas with lots of humans.
“It is important that animals move, because in moving they carry out important ecological functions like transporting nutrients and seeds between different areas. Additionally, mammalian movements bring different species together and thus allow for interactions in food webs that might otherwise not occur. If mammals move less this could alter any of these ecosystem functions,” says lead author Marlee Tucker.
Across the wide array of species its data encompasses, the study points to a singular, and grim, conclusion: For mammal species, the effects of habitat loss and habitat fragmentation don’t discriminate by geographic location, body size, or where that species sits on the food chain — the human footprint threatens most other mammals.
“Ultimately, it would be good to know whether there are critical thresholds in the human footprint for the species living around us. Are there specific points beyond which resources become limiting and species are excluded?” he asked. “As we continue to transform the landscape and as the human population expands, we’re limiting the space and resources that other mammals need to live.”
Archaeologists say they may have discovered one of the earliest examples of a ‘crayon’ possibly used by our ancestors 10,000 years ago for applying colour to their animal skins or for artwork.
The ochre crayon was discovered near an ancient lake, now blanketed in peat, near Scarborough, North Yorkshire. An ochre pebble was found at another site on the opposite side of the lake.
The pebble had a heavily striated surface that is likely to have been scraped to produce a red pigment powder. The crayon measures 22mm long and 7mm wide.
Ochre is an important mineral pigment used by prehistoric hunter-gatherers across the globe. The latest finds suggest people collected ochre and processed it in different ways during the Mesolithic period.
The ochre objects were studied as part of an interdisciplinary collaboration between the Departments of Archaeology and Physics at the University of York, using state-of-the-art techniques to establish their composition.
The artefacts were found at Seamer Carr and Flixton School House. Both sites are situated in a landscape rich in prehistory, including one of the most famous Mesolithic sites in Europe, Star Carr.
A pendant was discovered at Star Carr in 2015 and is the earliest known Mesolithic art in Britain. Here, more than 30 red deer antler headdresses were found which may have been used as a disguise in hunting, or during ritual performances by shamans when communicating with animal spirits.
Lead author, Dr Andy Needham from the University of York’s Department of Archaeology, said the latest discoveries helped further our understanding of Mesolithic life.
He commented: “Colour was a very significant part of hunter-gatherer life and ochre gives you a very vibrant red colour. It is very important in the Mesolithic period and seems to be used in a number of ways.
“One of the latest objects we have found looks exactly like a crayon; the tip is faceted and has gone from a rounded end to a really sharpened end, suggesting it has been used.
“For me it is a very significant object and helps us build a bigger picture of what life was like in the area; it suggests it would have been a very colourful place.”
The research team say Flixton was a key location in the Mesolithic period and the two objects help paint a vibrant picture of how the people interacted with the local environment.
“The pebble and crayon were located in an area already rich in art. It is possible there could have been an artistic use for these objects, perhaps for colouring animal skins or for use in decorative artwork,” Dr Needham added.
Happiness is not a warm phone, according to a new study exploring the link between adolescent life satisfaction and screen time. Teens whose eyes are habitually glued to their smartphones are markedly unhappier, said study lead author and San Diego State University and professor of psychology Jean M. Twenge.
To investigate this link, Twenge, along with colleagues Gabrielle Martin at SDSU and W. Keith Campbell at the University of Georgia, crunched data from the Monitoring the Future (MtF) longitudinal study, a nationally representative survey of more than a million U.S. 8th-, 10th-, and 12th-graders. The survey asked students questions about how often they spent time on their phones, tablets and computers, as well as questions about their in-the-flesh social interactions and their overall happiness.
On average, they found that teens who spent more time in front of screen devices — playing computer games, using social media, texting and video chatting — were less happy than those who invested more time in non-screen activities like sports, reading newspapers and magazines, and face-to-face social interaction.
Twenge believes this screen time is driving unhappiness rather than the other way around.
“Although this study can’t show causation, several other studies have shown that more social media use leads to unhappiness, but unhappiness does not lead to more social media use,” said Twenge, author of “iGen: Why Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy — And Completely Unprepared for Adulthood.”
Total screen abstinence doesn’t lead to happiness either, Twenge found. The happiest teens used digital media a little less than an hour per day. But after a daily hour of screen time, unhappiness rises steadily along with increasing screen time.
“The key to digital media use and happiness is limited use,” Twenge said. “Aim to spend no more than two hours a day on digital media, and try to increase the amount of time you spend seeing friends face-to-face and exercising — two activities reliably linked to greater happiness.”
Looking at historical trends from the same age groups since the 1990s, the researchers found that the proliferation of screen devices over time coincided with a general drop-off in reported happiness in U.S. teens. Specifically, young people’s life satisfaction, self-esteem and happiness plummeted after 2012. That’s the year that the percentage of Americans who owned a smartphone rose above 50 percent, Twenge noted.
“By far the largest change in teens’ lives between 2012 and 2016 was the increase in the amount of time they spent on digital media, and the subsequent decline in in-person social activities and sleep,” she said. “The advent of the smartphone is the most plausible explanation for the sudden decrease in teens’ psychological well-being.”
Biologists at the Universities of St Andrews and Edinburgh have discovered why some crows ‘craft’ elaborate hooked tools out of branched twigs.
The new study,explores why crows go the extra mile rather than using simple, unmodified sticks to extract prey it allows them to get at hidden food several times faster than if they used basic (non-hooked) tools.
New Caledonian crows are famous for their use of tools to winkle beetle grubs and other small prey out of hiding places. Although crows are capable of extracting food with straight twigs, in some areas they actively manufacture hooked stick tools before going hunting.
“It’s a painstaking sequence of behaviours,” explains lead author Dr James St Clair, from the School of Biology, University of St Andrews. “Crows seek out particular plant species, harvest a forked twig, and then — firmly holding it underfoot — carve, nibble and peel its tip, until it has a neat little hook.”
Biologists have long assumed that there was some benefit to crows manufacturing hooked tools, but had no idea just how much better they might be. The Scottish team conducted experiments to record how long wild-caught crows took to extract food from a range of naturalistic tasks, using either hooked or non-hooked tool designs.
Depending on the task, they found that hooked tools were between two and ten times more efficient than non-hooked tools. “That’s a huge difference!” says project leader, Professor Christian Rutz from the University of St Andrews. “Our results highlight that even relatively small changes to tool designs can significantly boost foraging performance.”
These new findings help explain why New Caledonian crows have evolved such remarkable tool-making abilities: “In nature, getting food quickly means that birds have more time and energy for reproduction and steering clear of predators. It’s really exciting that we were able to measure the benefits of these nifty crow tools.”
Scientists still don’t know how crows acquire the ‘know-how’ and make hooks; they may inherit the ability from their parents, or learn by observing experienced birds. Either way, because hooked-tool users will live longer and leave more offspring, the skill is expected to spread.
Researchers from North Carolina State University have developed a new technique for directly printing metal circuits, creating flexible, stretchable electronics. The technique can use multiple metals and substrates and is compatible with existing manufacturing systems that employ direct printing technologies.
“Flexible electronics hold promise for use in many fields, but there are significant manufacturing costs involved – which poses a challenge in making them practical for commercial use,” says Jingyan Dong.
“Our approach should reduce cost and offer an efficient means of producing circuits with high resolution, making them viable for integrating into commercial devices,” Dong says.
The technique uses existing electrohydrodynamic printing technology, which is already used in many manufacturing processes that use functional inks. But instead of ink, Dong’s team uses molten metal alloys with melting points as low as 60 degrees Celsius. The researchers have demonstrated their technique using three different alloys, printing on four different substrates: one glass, one paper and two stretchable polymers.
“This is direct printing,” Dong says. “There is no mask, no etching and no molds, making the process much more straightforward.”
The researchers tested the resilience of the circuits on a polymer substrate and found that the circuit’s conductivity was unaffected even after being bent 1,000 times. The circuits were still electrically stable even when stretched to 70 percent of tensile strain.
The researchers also found that the circuits are capable of “healing” themselves if they are broken by being bent or stretched too far.
“Because of the low melting point, you can simply heat the affected area up to around 70 degrees Celsius and the metal flows back together, repairing the relevant damage,” Dong says.
The researchers demonstrated the functionality of the printing technique by creating a high-density touch sensor, fitting a 400-pixel array into one square centimeter.
“We’ve demonstrated the resilience and functionality of our approach, and we’re open to working with the industry sector to implement the technique in manufacturing wearable sensors or other electronic devices,” Dong says.
Using the now-complete Cassini data set, Cornell astronomers have created a new global topographic map of Saturn’s moon Titan that has opened new windows into understanding its liquid flows and terrain.
Creating the map took about a year, according to doctoral student Paul Corlies, first author on “Titan’s Topography and Shape at the End of the Cassini Mission.” The map combines all of the Titan topography data from multiple sources. Since only about 9 percent of Titan has been observed in relatively high-resolution topography, with 25-30 percent of the topography imaged in lower resolution, the remainder of the moon was mapped using an interpolation algorithm and a global minimization process, which reduced errors such as those arising from spacecraft location.
The map revealed several new features on Titan, including new mountains, none higher than 700 meters. The map also provides a global view of the highs and lows of Titan’s topography, which enabled the scientists to confirm that two locations in the equatorial region of Titan are in fact depressions that could be either ancient, dried seas or cryovolcanic flows.
The map also revealed that Titan is a little bit flatter — more oblate — than was previously known, which suggests there is more variability in the thickness of Titan’s crust than previously thought.
“The main point of the work was to create a map for use by the scientific community,” said Corlies; within 30 minutes of the data set being available online, he began to receive inquiries on how to use it. The data set is downloadable in the form of the data that was observed, as well as that data plus interpolated data that was not observed. The map will be important for those modeling Titan’s climate, studying Titan’s shape and gravity, and testing interior models, as well as for those seeking to understand morphologic land forms on Titan.
Other Cornell authors on the paper are senior author Alex Hayes, assistant professor of astronomy, doctoral candidate Samuel Birch and research associate Valerio Poggiali.
The second paper, “Topographic Constraints on the Evolution and Connectivity of Titan’s Lacustrine Basins,” finds three important results using the new map’s topographical data. The team included Hayes, Corlies, Birch, Poggiali, research associate Marco Mastrogiuseppe and Roger Michaelides ’15.
The first result is that Titan’s three seas share a common equipotential surface, meaning they form a sea level, just as Earth’s oceans do. Either because there’s flow through the subsurface between the seas or because the channels between them allow enough liquid to pass through, the oceans on Titan are all at the same elevation.
“We’re measuring the elevation of a liquid surface on another body 10 astronomical units away from the sun to an accuracy of roughly 40 centimeters. Because we have such amazing accuracy we were able to see that between these two seas the elevation varied smoothly about 11 meters, relative to the center of mass of Titan, consistent with the expected change in the gravitational potential. We are measuring Titan’s geoid. This is the shape that the surface would take under the influence of gravity and rotation alone, which is the same shape that dominates Earth’s oceans,” said Hayes.
In graduate school: that Titan’s lakes communicate with each other through the subsurface. Hayes and his team measured the elevation of lakes filled with liquid as well as those that are now dry, and found that lakes exist hundreds of meters above sea level, and that within a watershed, the floors of the empty lakes are all at higher elevations than the filled lakes in their vicinity.
“We don’t see any empty lakes that are below the local filled lakes because, if they did go below that level, they would be filled themselves. This suggests that there’s flow in the subsurface and that they are communicating with each other,” said Hayes. “It’s also telling us that there is liquid hydrocarbon stored on the subsurface of Titan.”
The paper’s final result raises a new mystery for Titan. Researchers found that the vast majority of Titan’s lakes sit in sharp-edged depressions that “literally look like you took a cookie cutter and cut out holes in Titan’s surface,” Hayes said. The lakes are surrounded by high ridges, hundreds of meters high in some places.
The lakes seem to be formed the way karst is on Earth, in places like the Florida Everglades, where underlying material dissolves and the surface collapses, forming holes in the ground. The lakes on Titan, like Earth’s karst, are topographically closed, with no inflow or outflow channels. But Earth karst does not have sharp, raised rims.
The shape of the lakes indicates a process called uniform scarp retreat, where the borders of the lakes are expanding by a constant amount each time. The largest lake in the south, for example, looks like a series of smaller empty lakes that have coalesced or conglomerated into one big feature.
“But if these things do grow outward, does that mean you’re destroying and recreating the rims all the time and that the rims are moving outward with it? Understanding these things is in my opinion the lynchpin to understanding the evolution of the polar basins on Titan,” said Hayes.
Using x-ray lasers, researchers at Stockholm University have been able to map out how water fluctuates between two different states when it is cooled. At -44°C these fluctuations reach a maximum pointing to the fact that water can exist as two different distinct liquids.
Water, both common and necessary for life on earth, behaves very strangely in comparison with other substances. How water’s density, specific heat, viscosity and compressibility respond to changes in pressure and temperature is completely opposite to other liquids that we know.
We all are aware that all matter shrinks when it is cooled resulting in an increase in the density. We would therefore expect that water would have high density at the freezing point. However, if we look at a glass of ice water, everything is upside down, since we expect that water at 0°C being surrounded by ice should be at the bottom of the glass, but of course as we know ice cubes float. Strangely enough for the liquid state, water is the densest at 4 degrees C, and therefore it stays on the bottom whether it’s in a glass or in an ocean.
If you chill water below 4 degrees, it starts to expand again. If you continue to cool pure water (where the rate of crystallization is low) to below 0, it continues to expand — the expansion even speeds up when it gets colder. Many more properties such as compressibility and heat capacity become increasingly strange as water is cooled. Now researchers at Stockholm University, with the help of ultra-short x-ray pulses at x-ray lasers in Japan and South Korea, have succeeded in determining that water reaches the peak of its strange behaviour at -44°C.
Water is unique, as it can exist in two liquid states that have different ways of bonding the water molecules together. The water fluctuates between these states as if it can’t make up its mind and these fluctuations reach a maximum at -44°C. It is this ability to shift from one liquid state into another that gives water its unusual properties and since the fluctuations increase upon cooling also the strangeness increases.
“What was special was that we were able to X-ray unimaginably fast before the ice froze and could observe how it fluctuated between the two states,” says Anders Nilsson, Professor of Chemical Physics at Stockholm University. “For decades there has been speculations and different theories to explain these remarkable properties and why they got stronger when water becomes colder. Now we have found such a maximum, which means that there should also be a critical point at higher pressures.”
Another remarkable finding of the study is that the unusual properties are different between normal and heavy water and more enhanced for the lighter one. “The differences between the two isotopes, H2O and D2O, given here shows the importance of nuclear quantum effects,” says Kyung Hwan Kim, postdoc in Chemical Physics at Stockholm University. “The possibility to make new discoveries in a much studied topic such as water is totally fascinating and a great inspiration for my further studies,” says Alexander Späh, PhD student in Chemical Physics at Stockholm University.
“It was a dream come true to be able to measure water under such low temperature condition without freezing” says Harshad Pathak, postdoc in Chemical Physics at Stockholm University. “Many attempts over the world have been made to look for this maximum.”
“There has been an intense debate about the origin of the strange properties of water for over a century since the early work of Wolfgang Röntgen,” further explains Anders Nilsson. “Researchers studying the physics of water can now settle on the model that water has a critical point in the supercooled regime. The next stage is to find the location of the critical in terms of pressure and temperature. A big challenge in the next few years.”