- Not Exactly Rocket Science
Pocket Science – belly-flopping frogs, and fattening marmots
Not Exactly Pocket Science is a set of shorter write-ups of new stories with links to more detailed takes by the world’s best journalists and bloggers. It is meant to complement the usual fare of detailed pieces that are typical for this blog.
Frogs evolved to jump before they perfected landings
Most frogs are can leap large distances in a single bound, jumping forward with a thrust of their powerful hind legs and landing gracefully on their front ones. But it wasn’t always like this. A study of one of the most primitive groups of frogs suggests that the first frogs landed in an awkward belly-flop. These animals evolved to jump before they perfected their landings.
Virtually all frogs jump and land in the same way. But Richard Essner Jr from Southern Illinous University discovered a unique leaping style in the Rocky Mountain tailed frog. This species belongs to a group called the leiopelmatids, more commonly (and accurately) known as the “primitive frogs”. Using high-speed video footage, Essner showed that the tailed frog’s landings are an awkward mix of belly-flops, face-plants and lengthy skids. Only when it grinds to a halt does it gather its outstretched limbs together. By contrast, two more advanced species – the fire-bellied toad and the northern leopard frog – rotate their limbs forward in mid-air to land gracefully. The tailed frog managed to jump a similar distance, but its recovery time was longer.
These results support the idea that frogs eventually evolved their prodigious jumping abilities to escape from danger by rapidly diving into water. Landings hardly matter when you’re submerged and the ability to pull them off elegantly only evolved later. Essner thinks that doing so was fairly simple – if the tailed frog starts pulling its legs in just slightly earlier, it would land with far more poise. This simple innovation was probably a critical one in frog evolution. The primitive frogs never got there, but they have other ways of coping with their clumsy crash-landings. They’ve stayed very small to limit the injuries they sustain, and they have large shield-shaped piece of cartilage on their undersides to protect their soft vital organs.
Reference: Naturwissenschaften http://dx.doi.org/10.1007/s00114-010-0697-4; Video by Essner; soundtrack by me.
More on frogs: Tree frogs shake their bums to send threatening vibes, pesticide-stricken frogs, ‘Wolverine’ frogs, a lungless frog, and seven habits of highly successful toads
Changing climate fattens marmots
The media is rife with tales of animals from polar bears to corals suffering as a result of climate change. But some species stand to gain from the rising global temperatures. In Colorado’s Rocky Mountains, warmer climes allow the yellow-bellied marmot to awaken from its winter hibernation earlier. With more time available to eat, they become bigger and so do their populations. In just three decades, their numbers have tripled.
Arpat Ozgul from Imperial College London studied a 33-year census of Colorado’s marmots, where individuals have been tracked over their entire lifetimes. These rodents spend the winter hibernating in their burrows. But since 1976, they have been waking up earlier and earlier in the year, presumably because of a rise in warm days. That gives them more time to eat and grow before their next hibernation, and the adults have become around 10% heavier. Ozgul found that being fatter offers many advantages for a marmot – females are more likely to breed, youngsters grow more quickly, and adults are more likely to survive their next bout of hibernation.
It’s no surprise that their population has shot up dramatically, although surprisingly, this wasn’t a gradual process. Their numbers seemed to be fairly stable but they passed a tipping point in 2000 and have skyrocketed ever since. By modelling the changes in their bodies over time, Ozgul concluded that the marmots haven’t changed much genetically – their extra pounds are the result of their response to environmental changes. For example, the bluebells that they like to eat declined after 2000, which might have prompted them to seek other fattier foods.
But Ozgul worries that this boom period has a bust on the horizon – it’s a short-term response to warmer climate. These are animals that are adapted to chilly mountainous temperatures and they don’t fare well in heat. If temperatures continue to rise and summers get longer and drier, their health might suffer and their populations might crash.
More on this story from Jess McNally at Wired and Lucas Laursen at Nature
Reference: Nature http://dx.doi.org/10.1038/nature09210; image by Ben Hulsey
More on climate change and animal populations: The rise of “weedy” mice, the mystery of the shrinking sheep, lost clownfish, marching emperor penguins, and declining amphibians and reptiles
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