Climate Change Is Making Nearly All Sea Turtles Born on These Beaches Female


Climate change can wipe out a species's food source and destroy its habitat, but rising temperatures are having a more surprising effect on green sea turtles that's no less devastating. According to a report in Current Biology [PDF], up to 99.8 percent of the green sea turtles born on certain beaches in Australia are female, a direct result of the area's warmer-than-average temps.

A turtle's sex is determined by its environment. As The Washington Post reports, a clutch of eggs that incubates in sand that's roughly 85°F will produce about 50 percent females and 50 percent males. A few degrees cooler and the batch skews male; a bit hotter and it's majority female.

This evolutionary mechanism tends to balance itself out, but on beaches in northeast Australia, it's being hijacked by climate change. In order to gauge the size of the impact, researchers with the National Oceanic and Atmospheric Administration sampled the nesting beaches along the coast of Australia adjacent to the Great Barrier Reef, the part that has seen the most dramatic temperature rises and coral bleaching. What they found on the warmer northern beaches was the worst-case scenario: 99.1 percent of juveniles, 99.8 percent of subadults, and 86.8 percent of the overall population was female. Data taken from the southern beaches are only slightly less alarming: Turtles hatched in the relatively cooler sands there were still 65 to 69 percent female. According to the study's authors, "the complete feminization of this population is possible in the near future." That would affect the species' future population growth.

Green sea turtles aren't the only species vulnerable to huge sex shifts by way of climate change. Many other reptiles also rely on temperature-dependent sex determination to keep populations balanced. But above-average temperatures can do more harm beyond messing with sex development: It can also kill embryos before they have the chance to hatch. The authors emphasize that figuring out how to regulate sand temperatures at key rookeries will be essential moving forward. If not, the species could face "a population collapse—or even extinction."

Lítla Dímun: The Smallest of the Faroe Islands Has Its Very Own Cloud

While some islands are known for their unusual geography or unique history, Lítla Dímun is notable for its weather. The island, which is the smallest of Denmark's Faroe Islands chain, is often capped by a lens-shaped cloud, making it resemble a scene from a fairytale.

According to Mental Floss's own Kerry Wolfe writing for Atlas Obscura, the cloud floating above Lítla Dímun is a lenticular cloud. This type of cloud forms when moist air flows over a protruding geological feature, like a mountain top. When the wind moving up the landmass hits the air current directly above it, a sort of wave is created on the downwind side of the mountain. The moist air falling down this wave evaporates and then condenses into a large, flying-saucer-shaped cloud atop the mountain peak as a result.

Another factor that makes Lítla Dímun distinct is that it's the only one of the 18 main Faroe Islands without human inhabitants. Visitors to the mystical location will instead find a thriving population of sheep. Originally, Lítla Dímun was home to a group of feral sheep likely dating back to the Neolithic era. But they were hunted to extinction in the 19th century. Domesticated sheep were introduced there around the same time, and today, farmers visit the island once a year to round up their flocks.

One of the few signs of human life are the ropes farmers use to scale the cliff faces bordering the island. Even if you have rock-climbing skills, Lítla Dímun may be dangerous to visit. A boat ride to the rocky shore is only possible when the surrounding sea is calm.

[h/t Atlas Obscura]

Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

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