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To don icy rings, don't be too dense
IN BRIEF
KEN BOHN / SAN DIEGO ZOO GLOBAL
IT MIGHT be the island air. New Caledonian crows are renowned for their ingenious use of tools for extracting hard-to-reach food. Now it turns out that their Hawaiian cousins are equally adept. Like the New Caledonian crow, the Hawaiian crow has large, mobile eyes and a straight bill. Christian Rutz at the University of St Andrews in the UK wondered whether these similarities would make them equally disposed to using tools. Hawaiian crows are extinct in the wild, but 109 birds still live in two captive breeding centres in Hawaii, which meant Rutz was able to test pretty much every member of the species. He stuffed food into holes in a log, and gave the birds a variety of sticks. Almost all of them used the sticks to get to the food, including young ones who had never seen adults use tools. Most extracted the food in less than a minute – even faster than the researchers were able to (Nature, doi.org/bqps). “It’s mind-blowing,” says Rutz. “They’re very good at getting the tool in the right position, and if they’re not happy with it they’ll modify it or make their own.” Rutz thinks islands with few predators or other birds hogging less accessible food gave these two species time and space to evolve the complex behaviour.
16 | NewScientist | 24 September 2016
Glowing protein reveals memory’s building blocks AT LAST, we’ve seen what might be the primary units of memory, lighting up in the brains of mice. Certain cells in our brains keep track of our location and how far we travel. The corresponding neurons in a rat’s brain fire in sequence when the animal is resting, as if it is mentally retracing its path – a process that probably helps memories form. But exactly what happens during these replays was unclear. Researchers have long suspected that the cells might fire together in small groups, but nobody could
watch them, says Rosa Cossart at the Institute of Neurobiology of the Mediterranean in Marseille, France. Using a fluorescent protein that lights up when neurons fire, Cossart and her team have now observed the activity of more than 1000 neurons in each of four mice when they were walking on a treadmill or standing still. As expected, when the mice were running, the neurons that track how far the animal has travelled fired in a sequential pattern. These same cells also lit
up while the mice were resting, but in a strange pattern. As the mice reflected on their memories, the neurons fired in the same sequence as when the animals were running. But rather than firing individually, they fired together in sequential blocks that corresponded to particular segments of the mouse’s run (Science, doi.org/bqpq). “We’ve been able to image the individual building blocks of memory,” Cossart says, each one reflecting a chunk of the mouse’s experience. NASA/JPL/SPACE SCIENCE INSTITUTE
Hawaiian crow is handy with tools
For new stories every day, visit newscientist.com/news
What came first: rattle or shake? SHAKE, rattle and strike. It is one of the most terrifying sounds in the animal kingdom, but how the rattlesnake evolved its chilling warning signal is a mystery. The evolution of the rattle has baffled scientists because, unlike other complex physical traits like eyes or feathers, it has no obvious precursor or intermediate stage. “There is no half-rattle,” says David Pfennig at the University of North Carolina at Chapel Hill. Now his study suggests the rattle evolved long after the tailshaking behaviour. His team prodded 56 species of venomous and non-venomous snakes with a fake rat on a stick and recorded their defensive tail shakes. They found that the more closely related a snake was to the rattlesnake, the more similar its tail shake was in speed and duration (The American Naturalist, doi.org/bqpv). “This suggests the defensive tail vibration came first, perhaps as a physiological response to stress, and that became a reliable cue to predators that the snake was about to strike,” says Pfennig. “When the rattle evolved, it became an even more effective signal.”
To don icy rings, don’t be too dense IT’S a new spin on things. Saturn’s rings might be the result of the planet eating a rotating icy rock. We think rings form when objects such as asteroids or comets pass too close to a planet and are pulverised by its gravity. But that fails to explain why Saturn’s rings are mostly water ice while other gas giants have rocky rings. “The origin of Saturn’s rings remains elusive,” says Ryuki Hyodo at Kobe University in Japan. Hyodo and his team modelled a planet’s gravity snaring objects into orbit. Some tumbled “forwards”, in the same sense as their orbit, and
others backwards. They found that bodies rotating forwards break up more easily, and their fragments are more efficiently sucked into orbit. To see why Saturn and Uranus have different kinds of rings, the team simulated realistic objects with an icy mantle around a hard, rocky core (arxiv.org/abs/1609.02396v1). In some Saturn scenarios, only the fragments from the outer, icy layer of were swept up, creating proto-rings that could evolve into what we see today. Uranus is denser than Saturn, so it seized more fragments from the rocky core to form its rings.
KEN BOHN / SAN DIEGO ZOO GLOBAL
IT MIGHT be the island air. New Caledonian crows are renowned for their ingenious use of tools for extracting hard-to-reach food. Now it turns out that their Hawaiian cousins are equally adept. Like the New Caledonian crow, the Hawaiian crow has large, mobile eyes and a straight bill. Christian Rutz at the University of St Andrews in the UK wondered whether these similarities would make them equally disposed to using tools. Hawaiian crows are extinct in the wild, but 109 birds still live in two captive breeding centres in Hawaii, which meant Rutz was able to test pretty much every member of the species. He stuffed food into holes in a log, and gave the birds a variety of sticks. Almost all of them used the sticks to get to the food, including young ones who had never seen adults use tools. Most extracted the food in less than a minute – even faster than the researchers were able to (Nature, doi.org/bqps). “It’s mind-blowing,” says Rutz. “They’re very good at getting the tool in the right position, and if they’re not happy with it they’ll modify it or make their own.” Rutz thinks islands with few predators or other birds hogging less accessible food gave these two species time and space to evolve the complex behaviour.
16 | NewScientist | 24 September 2016
Glowing protein reveals memory’s building blocks AT LAST, we’ve seen what might be the primary units of memory, lighting up in the brains of mice. Certain cells in our brains keep track of our location and how far we travel. The corresponding neurons in a rat’s brain fire in sequence when the animal is resting, as if it is mentally retracing its path – a process that probably helps memories form. But exactly what happens during these replays was unclear. Researchers have long suspected that the cells might fire together in small groups, but nobody could
watch them, says Rosa Cossart at the Institute of Neurobiology of the Mediterranean in Marseille, France. Using a fluorescent protein that lights up when neurons fire, Cossart and her team have now observed the activity of more than 1000 neurons in each of four mice when they were walking on a treadmill or standing still. As expected, when the mice were running, the neurons that track how far the animal has travelled fired in a sequential pattern. These same cells also lit
up while the mice were resting, but in a strange pattern. As the mice reflected on their memories, the neurons fired in the same sequence as when the animals were running. But rather than firing individually, they fired together in sequential blocks that corresponded to particular segments of the mouse’s run (Science, doi.org/bqpq). “We’ve been able to image the individual building blocks of memory,” Cossart says, each one reflecting a chunk of the mouse’s experience. NASA/JPL/SPACE SCIENCE INSTITUTE
Hawaiian crow is handy with tools
For new stories every day, visit newscientist.com/news
What came first: rattle or shake? SHAKE, rattle and strike. It is one of the most terrifying sounds in the animal kingdom, but how the rattlesnake evolved its chilling warning signal is a mystery. The evolution of the rattle has baffled scientists because, unlike other complex physical traits like eyes or feathers, it has no obvious precursor or intermediate stage. “There is no half-rattle,” says David Pfennig at the University of North Carolina at Chapel Hill. Now his study suggests the rattle evolved long after the tailshaking behaviour. His team prodded 56 species of venomous and non-venomous snakes with a fake rat on a stick and recorded their defensive tail shakes. They found that the more closely related a snake was to the rattlesnake, the more similar its tail shake was in speed and duration (The American Naturalist, doi.org/bqpv). “This suggests the defensive tail vibration came first, perhaps as a physiological response to stress, and that became a reliable cue to predators that the snake was about to strike,” says Pfennig. “When the rattle evolved, it became an even more effective signal.”
To don icy rings, don’t be too dense IT’S a new spin on things. Saturn’s rings might be the result of the planet eating a rotating icy rock. We think rings form when objects such as asteroids or comets pass too close to a planet and are pulverised by its gravity. But that fails to explain why Saturn’s rings are mostly water ice while other gas giants have rocky rings. “The origin of Saturn’s rings remains elusive,” says Ryuki Hyodo at Kobe University in Japan. Hyodo and his team modelled a planet’s gravity snaring objects into orbit. Some tumbled “forwards”, in the same sense as their orbit, and
others backwards. They found that bodies rotating forwards break up more easily, and their fragments are more efficiently sucked into orbit. To see why Saturn and Uranus have different kinds of rings, the team simulated realistic objects with an icy mantle around a hard, rocky core (arxiv.org/abs/1609.02396v1). In some Saturn scenarios, only the fragments from the outer, icy layer of were swept up, creating proto-rings that could evolve into what we see today. Uranus is denser than Saturn, so it seized more fragments from the rocky core to form its rings.