6 Animals That Are Rapidly Evolving

istock
istock

We sometimes think of evolution as a thing of the past, but it continues today, especially as environmental pressures force humans and animals to adapt to survive. Here, a few examples of animals evolving in real-time.

1. The lizard with extra sticky feet

The native green lizards that occupy the lower branches and trunks of Florida’s trees got a rude awakening when their invasive cousins, the brown lizards, moved in. Faced with limited resources and double the competition, the green lizards made a move: they abandoned the lower branches for the treetops. Up there, the limbs are thinner and smoother, so the green lizards’ bodies had to adapt to the environmental shift. To better cling to the smooth branches, their toepads grew bigger and their scales got stickier—in just 15 years and about 20 generations. “The degree and quickness with which they evolved was surprising," said Yoel Stuart, a postdoctoral researcher in the College of Natural Sciences at The University of Texas at Austin and lead author of the study. "If human height were evolving as fast as these lizards' toes, the height of an average American man would increase from about 5 foot 9 inches today to about 6 foot 4 inches within 20 generations." 

2. The shrimp that lost its eyes

In the process of evolutionary change, you either use it or you lose it—and this is certainly true for a group of cave-dwelling crustaceans. These crabs and shrimp live underground where there is no light, and the sense of sight doesn’t do much good. As a result, they’ve gone blind, relying on smell and touch to navigate the cavernous depths. When researchers compared the brains of these spelunkers to their land-dwelling relatives, they found that not only are these creatures sightless, they’re actually losing the parts of their brains associated with vision. Meanwhile, the areas that control touch and smell are getting bigger. "It's a nice example of life conditions changing the neuroanatomy," the study’s lead author, Dr. Martin Stegner, from the University of Rostock in Germany, told the BBC. It’s taken about 200 million years for the brain changes to occur, which may not seem “rapid,” but as the Washington Post’s Rachel Feltman says, it’s “a relatively short time, in the evolutionary scheme of things.”

3. The owls that are changing color

Climate change is forcing many animals to adapt to survive. The tawny owl in Finland is a good example. These creatures come in two colors, brown or pale grey. The cold white winters have traditionally favored the grey owls, which can hide from predators by blending into a snowy color scheme. But as the winters have become more mild over the last 50 years, researchers noticed a shift: grey owls are on the decline and the brown birds are thriving, better suited to blending into the bare brown branches of the forest. As more brown owls survive, more brown genes get passed down through generations. Until now, the researchers say, “an evolutionary response to a quantified selection pressure driven by climate change has not been empirically demonstrated in a wild population.”

4. The fish that’s migrating earlier

Climate change is also the driving force behind a recent behavioral shift in pink salmon. As water temperatures rise, the fish are migrating from the ocean to the river to spawn about two weeks earlier than they did 40 years ago. And this isn’t just a new behavior—it’s actually a change at the genetic level. Between the 1980s and 2011, the number of late-migrating salmon declined by 20 percent, according to Ryan Kovach, a population ecologist at the University of Alaska in Fairbanks. The change happened over just one or two generations, which suggests organisms can adapt to climate change very quickly. “We show that there has been a genetic shift towards earlier migration timing through what appears to be natural selection against the late-migrating individuals in the population,” Kovach says

5. The bedbugs with super-strength

Unfortunately, our long-running battle with these bed-hopping pests has backfired, producing bedbugs with thicker shells and nerve cells of steel to resist the harsh chemicals we lob at them. Bedbugs in New York City are now 250 times more resistant to pesticides than the bedbugs in Florida, according to researchers at the University of Massachusetts in Amherst. "Insect resistance is nothing more than sped-up evolution," says insect toxicologist John Clark. 

6. The mouse that’s immune to poison

Bad news for anyone with a fear of mice: researchers have discovered a house mouse with an immunity to Warfarin, a type of poison typically deployed to fight infestations. The super mice were discovered in Germany, where the lowly house mouse bred with its poison-resistant distant cousin the Algerian mouse. The result? A hybrid mouse with a very useful genetic mutation that gives it a leg up over its rodent relatives. Usually hybrid animals can’t reproduce, but "sometimes there is the occasional odd hybrid that has just about the right novel combination of genomes from two species that renders them, at least temporarily, superior over the pure species," says the study’s lead author Michael Kohn. “We’ve caught evolution in the act.” 

All images courtesy of iStock unless otherwise noted.

Why Do Dogs Sniff Each Other's Butts?

Chloe Effron // Dogs: iStock
Chloe Effron // Dogs: iStock

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

We might giggle when we see dogs sniffing each other’s rear ends, but there’s a good reason why dogs stick their noses in private places. It lets them find out all kinds of things about each other to help them get along and survive. A butt sniff for dogs is like a handshake for humans.

Dogs’ amazing sense of smell is 10,000 to 100,000 times better than humans. They also have a special part of their noses called the Jacobson's organ that lets them ignore the smell of poop when they sniff another dog’s rear. Instead, the organ detects something more important. On the sides of a dog’s anus (AY-nuss)—the place where poop comes out—are special glands that release chemicals telling the body how to grow and work properly. This is what interests dogs the most about each other’s butts. 

The chemicals tell dogs a lot about each other. They help a dog to know if another dog is male or female, how old it is, what it eats, how healthy it is, and even what kind of mood they’re in. The chemicals also help it to know if other dogs are strangers or if they’ve met before. All of this helps dogs decide how they should behave. It's how dogs first get to know each other!

To sniff out more information about dogs and their noses (and their butts!), see this video by Reactions.

Do Lobsters Really Mate for Life?

iStock
iStock

It's a pop culture trope that mated lobsters stay together until they die. But is it true?

Nope. While plenty of animals practice long-term monogamy, lobsters are not among them. Lobsters actually mate by a weird system of serial monogamy. It's not exactly a one-night stand, but it's not a lifelong commitment either. Instead, a bunch of females take turns having a fling with the local dominant male that lasts a week or two and, if they're not happy with the amount of genetic material he's provided, then seek a little extra action.

It works like this: A female lobster who's ready to mate (which they can only do right after they've molted) hangs out near the den of the local dominant male and fans her pheromone-laced urine into his home. This relaxes the male, making him less aggressive and more receptive to mating. Then there's a brief courtship, and the male allows the female into his den.

Anywhere from a few hours to a few days later, the female slips into something a little more comfortable by shedding her exoskeleton. (Shacking up with the neighborhood tough guy guarantees her protection during this vulnerable time.) The pair mates, and the male deposits his sperm in the female. Once her new shell has hardened a week or two later, she takes off, and another female can have her turn. Often, the females in an area will stagger the timing of their molts to make their reproductive conga line more efficient. As soon as one female is done with the stud, the next one is already waiting to pee on his doorstep.

Sometimes, the male doesn't provide enough sperm to fully fertilize all of a female's eggs. In these cases, she'll leave before her new shell finishes forming to find and mate with another male (or males) until she collects enough sperm. Usually this requires just an extra dalliance or two, but as many as 10 have been reported.

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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