Curio Cabinet

It's Flashback Friday! In honor of Squirrel Appreciation Day, enjoy these bushy-tailed, nature-focused curios.
 
You might call them nature’s summer soundtrack. Last year’s emergence of Brood X cicadas guaranteed that just about everyone in the midwestern and southwestern U.S. got to hear these insects’ songs. Cicadas are some of the noisiest creatures in the entire animal kingdom, but how can something so small be so loud, and why do they leave those odd-looking shells everywhere? To understand that, one must understand cicadas’ unique anatomy and life-cycle.
 
There are more than 3,000 species of cicada, all belonging to the superfamily Cicadoidea. They occupy the same suborder (Auchenorrhyncha) as bugs like leafhoppers, and can be found on every continent on earth other than Antarctica. Male cicadas are best known for gathering in treetops to sing a thrumming, undulating song that can reach 90 decibels–about the same noise-level as a lawn mower. This song has two purposes: it attracts female cicadas to the area and repels predatory birds, which are sensitive to loud noises. Groups of male cicadas can also use a special “alarm” call to alert others to danger. That’s not to say that female cicadas don’t also make noise. They produce a more subtle clicking sound to let males know where they are. Because of this, confused male cicadas are sometimes drawn to other loud clicking noises, like those produced by power tools. Luckily, adult cicadas don’t bite or sting!
 
Cicadas have evolved to be as loud as possible. Their bodies are similar to the bodies of some musical instruments, like guitars, in that they’re full of empty air pockets which act as resonating chambers. The real secret to the male cicada’s song, however, are special organs on the underside of their abdomens called tymbals. Each tymbal is made of a thin membrane which connects to thicker sections called ribs. When a male cicada uses its muscles to buckle the tymbals, the ribs are pulled together to make a sharp clicking sound. They make the same sound again when they snap back to their original position. Incredibly, male cicadas are able to repeat this motion around 300 to 400 times per second, producing their characteristic thrum. Individual cicadas even time their thrums slightly out of sync with one another, so that the group doesn’t start or stop all at once. This makes their song seem continuous, even when some individuals are taking a break.
 
If all goes well, the cicadas’ song will help males and females find one another and mate. The female then lays around 200-400 eggs under the bark of trees or bushes using a special, needle-like organ on her abdomen. She dies shortly thereafter, since adult cicadas live for less than two months. After four to six weeks, her eggs hatch, and cicada nymphs emerge. A nymph is an immature, wingless form which will change as the cicadas grow. Cicada nymphs burrow underground shortly after hatching, where they feed on tree roots and grow slowly. Just how slowly depends on whether they belong to an annual or periodic species. While annual cicadas emerge every one to two years, periodic cicadas can stay underground for a whopping 15 to 17 years. Such is the case with this year’s famed Brood X. Annual and periodic cicadas have other notable differences, such as their overall color and size. Periodic cicadas are up to half an inch shorter than annual cicadas. They have black with red eyes while annual cicadas tend to be brown or green. Whether annual or periodic, however, once cicada nymphs emerge from the ground, they climb nearby objects and shed their exoskeletons, taking on their winged, adult forms. The empty exoskeletons they leave behind are sometimes mistaken for dead cicadas, but are merely empty "shells." Once their wings unfurl and dry, they take to the treetops and the whole, noisy cycle starts all over. Play it again, cicadas!
 
[Image description: A group of Brood X cicadas, with black bodies and red eyes, gather on a green plant.] Credit & copyright: Dan Keck, Wikimedia Commons, Public Domain

It's Flashback Friday! In honor of Squirrel Appreciation Day, enjoy these bushy-tailed, nature-focused curios.
 
Think this little guy knows he's famous? In late December, news broke that biologists working in Kenya's tropical Taita Hills had discovered a new species of tree hyrax. These small, furry African mammals bear a resemblance to rabbits and squirrels, though strangely they are more closely related to elephants. They are evasive, nocturnal, and quite noisy. Much of the hyrax's time is spent making complex vocalizations which can carry for miles. In late 2020, scientists set out to record these sounds. Previously, there were only three known species of tree hyrax: the Southern, Eastern, and Western hyraxes. However, along with calls from known hyrax species, other unknown-but-similar calls were recorded. Eventually, scientists even managed to snap a photo of the hyrax in question, which seemed to confirm that it was a previously unknown species. The new hyrax's call was unlike that of other hyraxes, which usually sound like sustained screams and can reach over 100 decibels. Scientists described the new sound as a "strangled thwack". Then again, who are we to judge a new species' singing voice?
 
Image credit & copyright: Hanna Rosti
 

It's Flashback Friday! In honor of Squirrel Appreciation Day, enjoy these bushy-tailed, nature-focused curios.
 
In the summertime, when the weather is hot, you might see a squirrel spread eagle in a prone position and wonder, "is that squirrel okay?" More likely than not, the squirrel is splooting. Also called pancaking or heat dumping, splooting is something that many mammals (koalas, bears, cats, dogs, raccoons, and foxes) do to cool down. No doubt you've seen a dog splay out on tile! For tree squirrels in hot climates, any surface will do: a bench, a railing, a shaded pathway. But not all squirrels sploot. Squirrels are one of the most diverse taxonomic families. The Sciuridae family—from the ancient Greek "skioros," meaning "shade tail")—has 278 species and 51 genera. It includes flying squirrels, tree squirrels, chipmunks, marmots, and prairie dogs. They live in North and South America, Africa, Europe, and Asia. Most sciurids are active during the day; they're diurnal. Tree squirrels are most common in cities, and spend their days gnawing at nuts, leaves, seeds, and small insects. Their four front teeth never stop growing, so they rely on this constant chewing to keep them a manageable size. Unlike other members of their family, tree squirrels do not estivate (go dormant) in summer. Instead, their bodies adapt to the changing temperatures. They're homeotherms, warm-blooded animals that can maintain a stable body temperature through different metabolic processes like shaking. In the winter, tree squirrels' belly hair thickens, making a lovely insulating coat. In the summer, their undercoat thins, revealing a nearly bare belly. When squirrels sploot, they press their chest against a cold surface to transfer excess heat. So refreshing after a day spent keeping those front teeth in check. Sploot on, (tree) squirrels!
 

Image credit & copyright: Natsuko, 2010
 

There’s magic in the air, scientifically speaking. On January 6, two groups of scientists published papers showcasing methods to collect DNA straight from the air. The teams came up with the idea independently and developed them concurrently, but didn’t know about each other until they were ready to publish their findings. One team was led by Elizabeth Clare of York University in Toronto, and the other by Kristine Bohmann of the University of Copenhagen in Denmark. While it has been possible for years to collect environmental DNA (eDNA) from water to monitor aquatic life, scientists believed that air wouldn’t be a good conductor of eDNA, since cells released into the air were assumed to drift too far too fast.
 
However, once researchers began testing for eDNA in the air, they found that they were able to collect a shocking amount of it. Both teams tested their methods in zoos, where they were sure to find non-native fauna that would stand out in their samples. At the Copenhagen Zoo in Denmark, Bohmann’s team was able to collect eDNA from 49 different animal species using relatively simple devices. They even tested a commercial vacuum cleaner and found that it worked, and they built a homemade vacuum with a small fan and some 3D printed parts to use in their experiments. Their results provided proof that this new method of eDNA collection could be used to monitor populations of land animals. Bohmann told NPR, "We even detected the guppy that was living in the pond in the rainforest house. It was just absolutely mind-blowing." In the end, neither team was upset when they found out that someone else was working on the same thing. Clare told NPR, "I think, we both thought, the papers are stronger together." Great minds think alike!

[Image description: A mother and baby elephant walk inside their zoo habitat.] Credit & copyright: Pixel-mixer, Pixabay
 

Want to know how old a fossil is? Have you tried ashing it? On January 12, a team of scientists led by volcanologist Céline Vidal published a study in the journal Nature showing that human life may be older than previously thought. The study centered around the age of Omo I, the skull fragments of a Homo sapiens individual who once lived in the Omo Kibish Formation in southwestern Ethiopia. When Omo I was discovered in 1967 by Richard Leakey, scientists used freshwater mollusk shells present around the fossil to date it, concluding that the skull was around 130,000 years old. But as technology improved, the fossil was tested again. In 2005, a new test measuring the decay of radioactive argon in nearby rocks showed that Omo I was around 196,000 years old.
 
For decades since its discovery, the fossil was considered to be the oldest Homo sapiens skull. But just how old? Vidal and her team took a new approach when looking into Omo I’s true age. Vidal is an expert on the impact of ancient volcanic eruptions and their effect on climate and civilizations. In an interview with Smithsonian Magazine, she explained, “Each eruption has a unique geochemical composition, a kind of fingerprint which we can use to try to figure out exactly which eruption on the Ethiopian Rift would have created a layer of volcanic ash.” This knowledge led her to analyze the geochemical composition of the ashes left on the layer on top of where Omo I was found. She concluded that they came from an eruption from the Shala Volcano 233,000 years ago. That means that the oldest confirmed human fossil is at least that old—nearly 40,000 years older than previously thought. As exciting as the discovery is, Vidal isn’t done with her work yet. If the volcanologist and her team can find a layer of ash below where Omo I was found, they might be able to figure out the maximum age of the fossil using the same technique.Amazing how a blast from the past is rewriting prehistory.

 
[Image description: A reproduction of the Omo Remains, of which Omo I is a part, at the Museum of Black Civilizations in Dakar.] Credit & copyright: GuillaumeG, Wikimedia Commons, image cropped for size.