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Swimming with Giant Sloths

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Wikimedia Commons

Sloths aren’t the most impressive swimmers. When today’s two- and three-toed sloths take a dip, they bob along in an awkward doggy paddle. But there used to be sloths that evolution had specifically adapted to be at home in the water. Over the course of four million years, one lineage of giant sloth shuffled into the seas.

The classic image of a giant sloth is of a bulky mammal lazily plucking leaves in an Ice Age forest. But the swimming sloths—named Thalassocnus—lived along the beaches of Peru between 8 and 4 million years ago. There were no tree stands here for the sloths to waddle among. The sea met the desert, and it was in the waves that the sloths found their food.

Since these sloths were first described from Peru’s Pisco Formation in 1995, paleontologists have identified five Thalassocnus species that lived along the same seaside one right after the other. And, paired with the fact that they were found with marine animals, the skeletons of these sloths suggested that the herbivores were at home foraging in the shallows. From the first species to the last, Thalassocnus looked like a seaside sloth.

But how did Thalassocnus go where no sloth had gone before? In a paper published in the Proceedings of the Royal Society B, paleontologist Eli Amson and colleagues at the Muséum national d'Histoire naturelle, Paris reveal that the secret of Thalassocnus lies inside the beast’s bones.

Compared to other mammals, sloths have unusually dense bones. This was true of the extinct giant sloths, too, and the successive species of Thalassocnus took this feature much further. After cutting into the ribs and limb bones of the first four Thalassocnus species, Amson and coauthors found that the bones of these sloths became increasingly dense until, in cross section, they had almost entirely lost their hollow central cavity. This condition is called osteosclerosis. And more than that, the sloth species show a swelling of some bones called pachyostosis that allowed the mammals to pack more bone tissue on.

Paleontologists have seen these features in other amphibious mammals. The bones of the earliest whales and sea cows—mammals that were caught transitioning into a fully aquatic life—show the same characteristics. And these changes to bones were not pathological. They track the evolution of skeletons as bone ballast.

While lungs filled with air are vital to keep swimming mammals from drowning, they can also be a liability for diving. Big, air-filled lungs buoy submerged animals up. Denser, swollen bones allowed early whales, sea cows, and, yes, giant sloths to more easily achieve neutral buoyancy underwater and therefore use less energy to stay beneath the surface.

Thalassocnus was far from being the Michael Phelps of the sloth world, though. The sloth still retained the familiar, bulky body shape of its ancestors. Instead of becoming a streamlined swimmer, Thalassocnus probably favored a method used by marine iguanas today. Anchored down by hefty bones, the sloth gripped the bottom with huge claws and scooped up soft plants as it wafted in the surf. Sloths slurped seaweed by the sea shore.

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Animals
Elusive Butterfly Sighted in Scotland for the First Time in 133 Years

Conditions weren’t looking too promising for the white-letter hairstreak, an elusive butterfly that’s native to the UK. Threatened by habitat loss, the butterfly's numbers have dwindled by 96 percent since the 1970s, and the insect hasn’t even been spotted in Scotland since 1884. So you can imagine the surprise lepidopterists felt when a white-letter hairstreak was seen feeding in a field in Berwickshire, Scotland earlier in August, according to The Guardian.

A man named Iain Cowe noticed the butterfly and managed to capture it on camera. “It is not every day that something as special as this is found when out and about on a regular butterfly foray,” Cowe said in a statement provided by the UK's Butterfly Conservation. “It was a very ragged and worn individual found feeding on ragwort in the grassy edge of an arable field.”

The white-letter hairstreak is a small brown butterfly with a white “W”-shaped streak on the underside of its wings and a small orange spot on its hindwings. It’s not easily sighted, as it tends to spend most of its life feeding and breeding in treetops.

The butterfly’s preferred habitat is the elm tree, but an outbreak of Dutch elm disease—first noted the 1970s—forced the white-letter hairstreak to find new homes and food sources as millions of Britain's elm trees died. The threatened species has slowly spread north, and experts are now hopeful that Scotland could be a good home for the insect. (Dutch elm disease does exist in Scotland, but the nation also has a good amount of disease-resistant Wych elms.)

If a breeding colony is confirmed, the white-letter hairstreak will bump Scotland’s number of butterfly species that live and breed in the country up to 34. “We don’t have many butterfly species in Scotland so one more is very nice to have,” Paul Kirkland, director of Butterfly Conservation Scotland, said in a statement.

Prior to 1884, the only confirmed sighting of a white-letter hairstreak in Scotland was in 1859. However, the insect’s newfound presence in Scotland comes at a cost: The UK’s butterflies are moving north due to climate change, and the white-letter hairstreak’s arrival is “almost certainly due to the warming climate,” Kirkland said.

[h/t The Guardian]

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Animals
Plagued with Rodents, Members of the UK Parliament Demand a Cat
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Members of the United Kingdom’s Parliament want a cat, but not just for office cuddles: As The Telegraph reports, the Palace of Westminster—the meeting place of Parliament’s two houses, the House of Commons and the House of Lords—is overrun with vermin, and officials have had enough. They think an in-house feline would keep the rodents at bay and defray skyrocketing pest control costs.

Taxpayers in the UK recently had to bear the brunt of a $167,000 pest control bill after palace maintenance projects and office renovations disturbed mice and moths from their slumber. The bill—which was nearly one-third higher than the previous year’s—covered the cost of a full-time pest control technician and 1700 bait stations. That said, some Members of Parliament (MPs) think their problem could be solved the old-fashioned way: by deploying a talented mouser.

MP Penny Mordaunt tried taking matters into her own hands by bringing four cats—including her own pet kitty, Titania—to work. (“A great believer in credible deterrence, I’m applying the principle to the lower ministerial corridor mouse problem,” she tweeted.) This solution didn’t last long, however, as health and safety officials banned the cats from Parliament.

While cats aren’t allowed in Parliament, other government offices reportedly have in-house felines. And now, MPs—who are sick of mice getting into their food, running across desks, and scurrying around in the tearoom—are petitioning for the same luxury.

"This is so UNFAIR,” MP Stella Creasy said recently, according to The Telegraph. “When does Parliament get its own cats? We’ve got loads of mice (and some rats!) after all!" Plus, Creasy points out, a cat in Parliament is “YouTube gold in waiting!"

Animal charity Battersea Dogs & Cats Home wants to help, and says it’s been trying to convince Parliament to adopt a cat since 2014. "Battersea has over 130 years [experience] in re-homing rescue cats, and was the first choice for Downing Street, the Foreign and Commonwealth Office, and the Cabinet Office when they sought our mousers to help with their own rogue rodents,” charity head Lindsey Quinlan said in a statement quoted by The Telegraph. “We'd be more than happy to help the Houses of Parliament recruit their own chief mousers to eliminate their pest problem and restore order in the historic corridors of power."

As of now, only assistance and security dogs are allowed on palace premises—but considering that MPs spotted 217 mice alone in the first six months of 2017 alone, top brass may have to reconsider their rules and give elected officials purr-mission to get their own feline office companions.

[h/t The Telegraph]

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