How Bugs From Australia Settled African Islands

When the Mascarene islands—Mauritius, Réunion, and Rodrigues—were born, they were blank slates. Unlike some other islands, they didn’t break off from a larger landmass, taking plants and animals with them. Instead, they rose right out of the water, formed by volcanic activity in the Indian Ocean off the coast of East Africa. Life there had to start from scratch. 

The islands collected colonizers and wayward travelers—a seed here, an egg there—over about 10 million years. Some of these species, like the islands’ most famous resident, the dodo, are no longer around, but, German zoologist Sven Bradler says, the Mascarenes are still home to a “remarkably diverse, endemic, and threatened concentration of flora and fauna.”

The islands’ location led scientists to assume that the plants and animals there arrived from nearby Madagascar and the African mainland. That’s the case for most of them, but Bradler’s research, recently published in the journal BMC Evolutionary Biology, has revealed that at least some traveled from much farther away: Australia.  

Among the Mascarenes’ animals are several types of Phasmatodeans, commonly called stick bugs or walking sticks. These large insects mimic plants for camouflage. The Mascarene stick bugs are diverse in appearance and behavior, but share some similarities with other African stick bugs. Traditionally, they’ve been placed in four different groups and descend, the thinking goes, from different, unrelated lineages of African stick bugs that all found their way to the islands at different times. 

When Bradler and his team mapped out the evolutionary histories and relationships of 120 stick bug species from around the world (including, for the first time, the ones on the Mascarenes and elsewhere in the Indian Ocean), though, they found that this traditional view was way off the mark. 

Their results suggest that the Mascarene stick bugs aren’t the descendants of several types of African bugs that made separate journeys to the islands; in fact, they don’t appear to be closely related to African stick bugs at all. Instead, they descend from a lone species of stick bug that originated in Australia, some 3000 miles away. This common ancestor was a member of bug group Lanceocercata, from which they diverged around 22 million years ago. Over time, the Mascarene insects evolved and diversified, and converged on some of the same traits and features as their African neighbors, leading to confusing similarities. 

The trip from Australia to the Mascarenes would be a long, perilous one for most animals, and stick bugs seem to be at a distinct disadvantage when it comes to such long-distance travel. While many species have wings, they’re poor flyers and can usually only use their wings to slow their descent from trees to the ground. They’re not cut out for trans-oceanic journeys—but with some luck, their eggs could pull it off. Stick insect eggs are hard-shelled and seed-like, and can survive for months at a time floating on water. The researchers think that the eggs of the Masacarene bugs’ Australian ancestor floated on a strong ocean current to get to the islands, maybe attached to a stick (how apt) that acted like a raft for them.

If you’ve been paying attention to the numbers, you might have noticed that something is amiss with this explanation: These bugs are far older than the islands they call home. While the Mascarenes’ founding stick bugs appear to have arrived around 22 million years ago, the oldest of the islands only formed 8–10 million years ago.

There's a possible explanation for this mismatched timeframe. There’s evidence that the Mascarenes had sibling islands, formed from the same volcanic hot spot, that rose above sea level around 30 million years ago and have since sunk back under the ocean. Bradler thinks that the Australian stick bug’s eggs likely landed on one of these lost islands and the bugs used them as stepping stones to get where they are now. When the colonists hatched, they evolved and speciated before moving on to the newly formed Mascarenes. 

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How Does Catnip Work?
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If you have a cat, you probably keep a supply of catnip at home. Many cats are irresistibly drawn to the herb, and respond excitedly to its scent, rubbing against it, rolling around on the floor, and otherwise going nuts. There are few things that can get felines quite as riled up as a whiff of catnip—not even the most delicious treats. But why does catnip, as opposed to any other plant, have such a profound effect on our feline friends?

Catnip, or Nepeta cataria, is a member of the mint family. It contains a compound called nepetalactone, which is what causes the characteristic catnip reaction. Contrary to what you might expect, the reaction isn’t pheromone related—even though pheromones are the smelly chemicals we usually associate with a change in behavior. While pheromones bind to a set of specialized receptors in what’s known as a vomeronasal organ, located in the roof of a cat's mouth (which is why they sometimes open their mouths to detect pheromones), nepetalactone binds to olfactory receptors at the olfactory epithelium, or the tissue that lines the mucus membranes inside a cat’s nose and is linked to smell.

Scientists know the basics of the chemical structure of nepetalactone, but how it causes excitement in cats is less clear. “We don’t know the full mechanisms of how the binding of these compounds to the receptors in the nose ultimately changes their behavior,” as Bruce Kornreich, associate director of the Cornell Feline Health Center, tells Mental Floss. Sadly, sticking a bunch of cats in an MRI machine with catnip and analyzing their brain activity isn’t really feasible, either from a practical or a financial standpoint, so it’s hard to determine which parts of a cat’s brain are reacting to the chemical as they frolic and play.

Though it may look like they’re getting high, catnip doesn’t appear to be harmful or addictive to cats. The euphoric period only lasts for a short time before cats become temporarily immune to its charms, meaning that it’s hard for them to overdo it.

“Cats do seem to limit themselves," Michael Topper, president of the American Veterinary Medical Association, tells Mental Floss. "Their stimulation lasts for about 10 minutes, then it sort of goes away.” While you may not want to turn your house into a greenhouse for catnip and let your feline friend run loose, it’s a useful way to keep indoor cats—whose environment isn’t always the most thrilling—stimulated and happy. (If you need proof of just how much cats love this herb, we suggest checking out Cats on Catnip, a new book of photography from professional cat photographer Andrew Martilla featuring dozens of images of cats playing around with catnip.)

That said, not all cats respond to catnip. According to Topper, an estimated 70 percent of cats react to catnip, and it appears to have a genetic basis. Topper compares it to the genetic variation that causes some individuals to smell asparagus pee while others don’t. Even if a cat will eventually love the smell of catnip, it doesn’t come out of the womb yearning for a sniff. Young kittens don’t show any behavioral response to it, and may not develop one until several months after birth [PDF].

But some researchers contend that more cats may respond to catnip than we actually realize. In one 2017 study, a group of researchers in Mexico examined how cats might subtly respond to catnip in ways that aren’t always as obvious as rolling around on the floor with their tongue hanging out. It found that 80 percent of cats responded to catnip in a passive way, showing decreased motor activity and sitting the “sphinx” position, an indicator of a relaxed state.

There are also other plants that have similar effects on cats, some of which may appeal to a wider variety of felines than regular old catnip. In a 2017 study in the journal BMC Veterinary Research, researchers tested feline responses to not just catnip, but several other plants containing compounds similar in structure to nepetalactone, like valerian root, Tatarian honeysuckle, and silver vine. They found that 94 percent of cats responded to at least one of the plants, if not more than one. The majority of the cats that didn’t respond to catnip itself did respond to silver vine, suggesting that plant might be a potential alternative for cats that seem immune to catnip’s charms.

Despite the name, domestic cats aren’t the only species that love catnip. Many other feline species enjoy it, too, including lions and jaguars, though tigers are largely indifferent to it. The scent of the plant also attracts butterflies. (However, no matter what you’ve heard, humans can’t get high off it. When made into a tea, though, it reportedly has mild sedative effects.)

The reason Nepeta cataria releases nepetalactone doesn’t necessarily have to do with giving your cat a buzz. The fact that it gives cats that little charge of euphoria may be purely coincidental. The chemical is an insect repellant that the plant emits as a defense mechanism against pests like aphids. According to the American Chemical Society, nepetalactone attracts wasps and other insect predators that eat aphids, calling in protective reinforcements when the plant is in aphid-related distress. That it brings all the cats to the yard is just a side effect.

Because of this, catnip may have even more uses in the future beyond sending cats into a delighted frenzy. Rutgers University has spent more than a decade breeding a more potent version of catnip, called CR9, which produces more nepetalactone. It’s not just a matter of selling better cat toys; since catnip releases the compound to ward off insects, it’s also a great mosquito repellant, one that scientists hope can one day be adapted for human use. In that case, you might be as excited about catnip as your cat is.

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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12 Furry Facts About Red Pandas
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Red pandas have always lived in the shadow of the other, more famous panda. But now it's time to give the little guy its due.

1. THEY HAVE TWO EXTINCT RELATIVES.

Red panda in a tree.
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Currently, red pandas live in the Eastern Himalayas. But the first red panda fossil was found a little bit further afield than that—in the United Kingdom. In 1888, a fossil molar and lower jaw of a cougar-sized animal called the Giant Panda (unrelated to the modern giant panda) were discovered. More fossils have been found in Spain, Eastern Europe, and even the United States. Around 5 million years ago, Tennessee was home to a giant red panda that probably went extinct with the arrival of raccoons.

2. THEY'RE VEGETARIAN CARNIVORES.

Red panda eating bamboo.
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It might seem like an oxymoron, but carnivore in this case doesn't mean meat eater. Carnivore is a biological order that includes groups like bears, dogs, and cats, and while these animals are generally carnivores, some are omnivores, and some are vegetarians. Red pandas are classified as carnivores because they're descended from the same ancestors as the other carnivores, but they rarely eat anything other than bamboo and a few insects. And while giant pandas eat all of a bamboo plant, red pandas eat only the young leaves. Because this is such a nutritionally poor food source, they need to spend 13 hours a day eating and looking for food and can lose upwards of 15 percent of their body weight in winter.

3. THEY'RE SLIGHTLY BIGGER THAN A DOMESTIC CAT.

Red panda sleeping on a branch.
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But their tails add as much as 18 inches to their length. Red pandas live solitary lives in trees, high up in the mountains, so they wrap those big, bushy tails around themselves to keep warm. (They also use them for balance.)

4. THEY HAVE A FALSE THUMB.

Red panda perched on a log.
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This is another feature (along with diet) that red pandas and giant pandas share. Because both pandas have false thumbs—which is actually an extended wrist bone—it was thought that it must be an adaption to eating bamboo. But the red panda's more carnivorous ancestors had this feature as well. According to a 2006 study, what happened was "one of the most dramatic cases of convergence among vertebrates." Convergent evolution is when two unrelated animals faced with similar circumstances evolve to look similar. In this case, the red panda's false thumb evolved to help it climb trees, and only later became adapted for the bamboo diet, while giant pandas evolved this virtually identical feature because of their bamboo diet.

5. THEY'RE ESCAPE ARTISTS.

Red panda climbing across a tree.
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Rusty the red panda had been at the Smithsonian National Zoo for just three weeks when he made a break for it in June 2013. His method of escape? A tree branch that was pushed down over his enclosure's electric fence by heavy rains. The ensuing panda hunt (and endless bad jokes about panda-monium) captivated Twitter (tweeters used the hashtag #findrusty) until he was found in a nearby neighborhood. Soon after his daring escape, Rusty became a father, forcing him to put his wild youth behind him and settle down. But it could have been worse. After a similar escape in Dresden, Germany, the authorities got another red panda down from a tree by using a fire hose to spray it with water. The panda fell 30 feet to the ground, giving it a concussion. (Ultimately, the animal was OK.)

Red pandas have also escaped from zoos in London, Birmingham, and Rotterdam. The Association of Zoos and Aquariums even warn in their official care manual "beware: red pandas are escape artists" [PDF].

6. ONE ESCAPE LED TO SOMETHING CALLED THE RED PANDA EFFECT.

Red panda peeking out from behind some tree branches.
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Sadly, the red panda involved in the 1978 Rotterdam escape was found dead not long after the search for it began. But the event led to a very peculiar psychological observation. Even after the body of the panda was found, more than 100 people reported seeing it, very much alive. These sightings were clearly mistaken; there's no reason to think that multiple red pandas were loose in Rotterdam, and red pandas are distinctive enough that mistaking them for a dog or cat was unlikely. It's believed that people expected to see a red panda, so they saw one, even though there wasn't one there; researchers called it the Red Panda Effect.

7. THERE'S AN INTERNET BROWSER NAMED AFTER THEM.

The Mozilla Firefox logo.
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Mozilla's flagship browser, Firefox, means red panda. Originally, Mozilla wanted to name the browser Firebird, but found that another open source project was using that name. Not wanting to upset anyone, they decided to go with Firefox, another name for the red panda. And in a true example of adorableness, in 2010 Mozilla adopted two baby red pandas that had been born at Tennessee's Knoxville Zoo.

8. THERE IS ONLY ONE TRUE PANDA—AND YOU CAN PROBABLY GUESS WHICH ONE IT IS.

Engraving of a parti-colored bear.
Engraving of a parti-colored bear, from The New Natural History Volume II by Richard Lydekker, 1901.

After the red panda was discovered in the 1820s, it was just called the panda (the origin of the name is controversial, but it probably comes from the Nepali word ponya, meaning "bamboo or plant eating animal"). Forty years later, Europeans found a new animal in China and called it the Parti-Colored bear—because unlike polar bears, black bears, or brown bears it was multi-colored.

9. THERE HAS BEEN A 140-YEAR TAXONOMIC MIX-UP.

A red panda walking toward the camera.
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Prepare to be confused: In the late 19th century, scientists noticed that the parti-colored bear and the (red) panda were very similar. Their jaws were more like each other than they were like any other animal, they lived near each other, they both had false thumbs, and their diets were similar. The decision was made to officially consider the (red) panda as a type of bear.

By the early 20th century, that decision was reversed: Parti-colored bears were declared bears, and (red) pandas were classified as cousins of the raccoon.

Then, in the 1910s, it was decided that parti-colored bears weren't actually bears at all, but were actually large pandas, and also distant relatives of the raccoon. But because parti-colored bears weren't classed as bears anymore, they had to have a name change. They became giant pandas, while the one true panda was renamed the red or lesser panda (to quote a 1920 issue of Popular Science: "Zoologists reverently refer to this rare beast as the "giant panda." Its more popular cognomen is the 'bear-raccoon'").

10. BUT RED PANDAS ARE THEIR OWN THING.

Two red pandas touch noses.
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By the 1980s, genetic evidence indicated that giant pandas actually were a type of bear, and red pandas belonged in their own family, the Ailuridae. They might seem similar, but they're not related.

All of this means that if you're the type of person who rolls their eyes when someone calls a bison a buffalo, or a koala a bear, you need to stop calling the bear a panda and instead refer to it as a "parti-colored bear," the original English name (but if you wanted to call it the bear-raccoon, no one would stop you). Giant pandas are not pandas. There is only one true panda.

11. BUT THIS DOESN'T AFFECT KUNG FU PANDA 3.

Red panda with teeth bared.
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There's still a kung fu panda in the series: Shifu, a red panda.

12. THEY'RE ENDANGERED.

Red panda laying down and sticking his tongue out.
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According to the World Wildlife Fund, there are fewer than 10,000 red pandas left in the wild. Habitat destruction increases the species' chances of extinction.

This story originally ran in 2015.

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