Dinosaurs Great at Growing * Dinosaurs do the Duck Paddle * Monarch Butterflies Navigate Without Map * Shark Tooth Weapons Reveal Lost Species * Humans Caused Bird Extinctions in Pacific Islands * Electric Engines for Aircraft

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This week, we have two exciting dinosaur discoveries involving Canadian researchers, one looking at  how dinosaurs grew, and the other an insight into  how they might have swum. Plus, we'll find out how monarch butterflies manage to keep their course; we'll hear about Pacific islanders who made ferocious weapons from shark's teeth; we'll learn how humans pushed hundreds of bird species to extinction; and we'll hear about the latest idea for airplane propulsion.

 

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Dinosaurs Great at Growing

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Reconstruction of an embryonic dinosaur inside an egg by D. Mazierski.  Click to enlarge
The discovery of a new bed of bones from embryonic dinosaurs is helping to reveal part of how they managed to grow so large.  Professor Robert Reisz, a paleontologist in the Department of Biology at the University of Toronto, Mississauga, and a large group of colleagues from several countries, have been studying bones that seem to have been deposited from a flood that destroyed a colonial nesting site.  The eggs in the site were broken open, and the bones buried for 200 million years.  These embryonic bones show incredibly rapid growth - far faster than any other vertebrate.
          
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Dinosaurs do the Duck Paddle

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Artist's impression of swimming dinosaur by N. Rogers.  Click to enlarge

Just when you thought it was safe to go back in the water, a team of scientists, including paleontologist Scott Persons, a PhD student at the University of Alberta, has found evidence of swimming in carnivorous dinosaurs.  The team found sets of scratches on a preserved river bottom that corresponded to the rear toe-claws of a bipedal carnivore.  The animal had been swimming in water of just the right depth, so that the claws of its paddling feet had cut through the sand at the bottom of the river bed. 

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Monarch Butterflies Navigate Without Map

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When monarch butterflies make their four-thousand-kilometre journey from eastern North America to their over-wintering grounds in Mexico, they use external cues, such as the Sun, as a compass.  This guides them in the necessary south-west direction to reach their destination.  But researchers, including Rachael Derbyshire, a Masters student from the Department of Integrative Biology at the University of Guelph, wanted to find out if monarchs could also use a 'map' if they experienced displaced longitude.  They discovered that monarchs from Ontario will also fly south-west when experimentally displaced in Calgary, and not south-east as a map would dictate.  This suggests they are not true navigators, instead using landmarks like the Rocky Mountains and bodies of water like the Gulf of Mexico to funnel their way to Mexico.

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Shark Tooth Weapons Reveal Lost Species

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Shark Tooth Weapon from The Gilbert Islands, Courtesy J. Drew
The Gilbert Islands, part of the island nation of Kiribati since 1979, are a chain of islands and atolls in the Central Pacific Ocean.  Because the waters around these islands are home to many species of shark, the people who live there have made sharks a significant part of their social customs and rituals for centuries.  One such custom has been to use shark teeth as adornments for weapons, including spears, lances, clubs, even a version of what we know as brass-knuckles.  Dr. Joshua Drew, a Lecturer in the Department of Ecology, Evolution and Environmental Biology at Columbia University in New York, studied the teeth from the weapons and discovered they come from two species of shark no longer located near those islands.  The dusky and spottail sharks likely became locally extinct as a result of visitors to the islands engaging in the shark fin trade.  The teeth from the two missing species are examples of shadow biodiversity; glimpses of the past that help guide conservation efforts for the future.

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Humans Caused Bird Extinctions in Pacific Islands

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Extinct Hawaiian Rail, by John Gerrard Keulemans. Click to enlarge
Human colonization of many Pacific islands, over a period of 800 to 3500 years ago, has proven to be a catastrophe for many species of non-perching birds.  A team of international scientists, including Dr. Alison Boyer, a Research Assistant Professor of Ecology and Evolutionary Biology at the University of Tennessee, studied fossils from 41 Pacific islands, including Hawaii and Fiji, and estimated that 983 species of birds have disappeared.  Some species were known to have existed, while many more in their estimate are still unknown.  The reasons for the extinction are directly related to human habitation, including over-hunting, loss of forest habitat and the introduction of  other species that preyed on birds.  Flightless birds - which were generally larger - were at the greatest risk of extinction.  Smaller islands lost more species because they were more easily deforested and provided fewer places for birds to hide.

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Electric Engines for Aircraft


Students testing hobby-type ion thruster
Dr Steven Barrett is hoping that a common science fair project might be the key to the first new idea in aircraft propulsion systems in decades.  Dr. Barrert, from the Department of Aeronautics and Astronautics at the Massachusetts Institute of Technology, has been testing the ionic wind thruster.  This device uses a high voltage to ionize air molecules, which are then attracted to an electrode.  The ionized air molecules push on neutral air molecules, producing thrust.  Dr. Barrett has found that this is a very efficient way to produce thrust - on the lab-bench, it's far more efficient than a jet engine.  His next step is to determine if the apparatus can be constructed in a way that might make it useful for aircraft.

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Theme music bed copyright Raphaël Gluckstein, Creative Commons License by-nc-nd-2.0