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Sea Creatures Are Getting Bigger

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While some animals—like dragonflies and penguins—have gotten smaller over time, sea creatures seem to be getting bigger. 

This news may not be particularly shocking—after all, living creatures started out as microscopic, and have evolved into things like the blue whale, currently the largest creature on Earth. Sure, it took a couple billion years to make that progress, but it happened. 

The idea that animals are always getting bigger is known as Cope's rule. Named after paleontologist Edward Drinker Cope, the rule suggests that animal lineages increase in body size over time. The hypothesis is based off the scientist's observations after looking at various fossils. The rule has been tested and documented for over a century, but a recent report published by Science provides the most convincing evidence yet.

A team led by Stanford University's Noel Heim analyzed more than 17,000 fossils of various marine animals, some as old as 542 million years. The study found that marine animals were, on average, 150 times larger than their Cambrian era counterparts.

"That's the size difference between a sea urchin that is about 2 inches long versus one that is nearly a foot long," said Noel Heim, a postdoctoral researcher in Payne's lab. "This may not seem like a lot, but it represents a big jump."

What's interesting is that not all the animals are getting bigger; this trend is being driven by larger animals surviving and diversifying to create more species.

"That's also something we didn't know before. For reasons that we don't completely understand, the classes with large body size appear to be the ones that over time have become differentially more diverse," said Jonathan Payne, a paleobiologist at Stanford School of Earth, Energy & Environmental Sciences.

The data leads scientists to believe that larger animals are evolutionarily favored, as there are many advantages to being greater in size. Larger size makes for a more formidable opponent, that can swim faster, burrow deeper, and eat larger prey. 

"As time marches forward, each species is assigned some probability of producing a new species, of remaining the same, or of going extinct, at which point it drops out of the race," Heim said.

The study will hopefully encourage other scientists to look for other trends in evolution. If size is a clear driving force, then perhaps evolution moves in other directional ways.

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Big Questions
What's the Difference Between Gophers and Groundhogs?
Gopher or groundhog? (If you chose gopher, you're correct.)
Gopher or groundhog? (If you chose gopher, you're correct.)
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Gophers and groundhogs. Groundhogs and gophers. They're both deceptively cuddly woodland rodents that scurry through underground tunnels and chow down on plants. But whether you're a nature nerd, a Golden Gophers football fan, or planning a pre-spring trip to Punxsutawney, Pennsylvania, you might want to know the difference between groundhogs and gophers.

Despite their similar appearances and burrowing habits, groundhogs and gophers don't have a whole lot in common—they don't even belong to the same family. For example, gophers belong to the family Geomyidae, a group that includes pocket gophers (sometimes referred to as "true" gophers), kangaroo rats, and pocket mice.

Groundhogs, meanwhile, are members of the Sciuridae (meaning shadow-tail) family and belong to the genus Marmota. Marmots are diurnal ground squirrels, Daniel Blumstein, a UCLA biologist and marmot expert, tells Mental Floss. "There are 15 species of marmot, and groundhogs are one of them," he explains.

Science aside, there are plenty of other visible differences between the two animals. Gophers, for example, have hairless tails, protruding yellow or brownish teeth, and fur-lined cheek pockets for storing food—all traits that make them different from groundhogs. The feet of gophers are often pink, while groundhogs have brown or black feet. And while the tiny gopher tends to weigh around two or so pounds, groundhogs can grow to around 13 pounds.

While both types of rodent eat mostly vegetation, gophers prefer roots and tubers (much to the dismay of gardeners trying to plant new specimens), while groundhogs like vegetation and fruits. This means that the former animals rarely emerge from their burrows, while the latter are more commonly seen out and about.

Groundhogs "have burrows underground they use for safety, and they hibernate in their burrows," Blumstein says. "They're active during the day above ground, eating a variety of plants and running back to their burrows to safety. If it's too hot, they'll go back into their burrow. If the weather gets crappy, they'll go back into their burrow during the day as well."

But that doesn't necessarily mean that gophers are the more reclusive of the two, as groundhogs famously hibernate during the winter. Gophers, on the other hand, remain active—and wreck lawns—year-round.

"What's really interesting is if you go to a place where there's gophers, in the spring, what you'll see are what is called eskers," or winding mounds of soil, Blumstein says [PDF]. "Basically, they dig all winter long through the earth, but then they tunnel through snow, and they leave dirt in these snow tunnels."

If all this rodent talk has you now thinking about woodchucks and other woodland creatures, know that groundhogs have plenty of nicknames, including "whistle-pig" and "woodchuck," while the only nicknames for gophers appear to be bitter monikers coined by Wisconsin Badgers fans.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Watch Christmas Island’s Annual Crab Migration on Google Street View
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Every year, the 45 million or so red crabs on the remote Australian territory of Christmas Island migrate en masse from their forest burrows down to the ocean to mate, and so the female crabs can release their eggs into the sea to hatch. The migration starts during the fall, and the number of crabs on the beach often peaks in December. This year, you don’t have to be on Christmas Island to witness the spectacular crustacean event, as New Atlas reports. You can see it on Google Street View.

Watching the sheer density of crabs scuttling across roads, boardwalks, and beaches is a rare visual treat. According to the Google blog, this year’s crabtacular finale is forecasted for December 16, and Parks Australia crab expert Alasdair Grigg will be there with the Street View Trekker to capture it. That is likely to be the day when crab populations on the beaches will be at their peak, giving you the best view of the action.

Crabs scuttle across the forest floor while a man with a Google Street View Trekker walks behind them.
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Google Street View is already a repository for a number of armchair travel experiences. You can digitally explore remote locations in Antarctica, recreations of ancient cities, and even the International Space Station. You can essentially see the whole world without ever logging off your computer.

Sadly, because Street View isn’t live, you won’t be able to see the migration as it happens. The image collection won’t be available until sometime in early 2018. But it’ll be worth the wait, we promise. For a sneak preview, watch Parks Australia’s video of the 2012 event here.

[h/t New Atlas]

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