The complex nature of the squirrels’ nests

How do squirrels build their nests so that they don’t fall apart and dump the baby squirrels? Squirrels’ nests, also called dreys, may look like haphazard clumps of leaves but are actually fairly complex in their construction, with several layers of different materials.

Tree squirrels also seek out advantageous locations with built-in support, like the juncture of several branches emerging from a tree trunk or a tangle of grape vines. Some squirrels build nests in tree cavities rather than among the high branches. The squirrel begins by roughly weaving a platform of live green twigs.

On top of this, soft, compressible materials like moss and damp leaves are added. Then an outer skeleton of twigs and vines is built around the insulated core, and finally, additional material fills in and strengthens the shell.

For the familiar grey squirrel, Sciurus carolinensis, the central cavity is about 6 to eight inches across. Smaller species build proportionally smaller nests. One study of nest materials used by European ground squirrels found that damp leaves and moss provided better insulation than dry lining materials.

A 2013 German hidden-camera study of a red squirrel filmed a nest being built in work periods totaling more than 3 1/2 hours over three days. The squirrel carried materials to the site with its mouth and front paws; bent stiffer twigs with its head and face; pushed other materials into place with its legs; shredded lining components by holding them with the front paws and chewing; and shaped the inner cavity by lying in it and turning around.

C Claiborne Ray

Deep-sea fishes are built to eat big
It’s cold and dark in the deep ocean. You eat what you can get. Here, big mouths help predators eat big prey. That may be why barbeled dragonfish have special head joints that allow them to open up their mouths 120 degrees and swallow big prey whole.
This flexible joint, described for the first time in a study recently, allows the fish to move its head to move up and out, permitting it to engulf large prey that can sustain it for long periods without additional food. Like the moray eel, barbeled dragonfish use a second set of teeth to pull the victim into their bodies for digestion.
Joanna Klein

Prehistoric ancestor unearthed
About 540 million years ago, our ancestors were insignificant creatures no more than one millimetre in size. They wriggled around in the sediments of shallow seas, gulped prey into their minuscule, baglike bodies and expelled the water through cone-shaped spouts around their mouths. Animals this small do not fossilise well, which is why this stage of the distant evolutionary past is so little known.

But a cache of 45 individuals has now been unearthed in Shaanxi province, in central China, in rock strata said to be some 540 million years old. The creatures are the oldest known members of an ancient group called deuterostomes, which are ancestral not just to humans but to a wide array of animals. Although slightly older animal fossils are known, they lie on branches of the tree of life that do not lead to humans.

Nicholas Wade

Ice that sparkles like diamonds
Large lumps scatter across a beach at the mouth of River Tokachi on Hokkaido, the northern island of Japan. They shine like diamonds beneath evening moon beams and glow like amber under a setting sun. At first glance, the scene looks like the remnants of a giant’s jewel heist gone wrong. But these glistening gems are just ice chunks, spit out by the river and tumbled by ocean waves.

They are called Tokachi river ice, jewellery ice or jewel ice, and they appear only here, and only during the coldest winter months. After locals began posting pictures, Japanese jewel ice went viral. When temperatures are well below freezing, the mouth of the crystal-clear river freezes over. The ice breaks into chunks that float out into the frigid ocean and then wash up on shore. There, the polished blocks accumulate and eventually melt into the sand. It’s the same type of hexagonal ice that snow crystals are made of.

“I had never heard of this type of ice and have never seen any sea ice like it,” wrote Peter Wadhams, an ocean physicist at the University of Cambridge who studies polar oceans and sea ice. “It’s just river ice, which is transparent because it has no salt in it.”
Joanna Klein

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