Anyone who’s seen the 1986 musical comedy, Little Shop of Horrors, is familiar with Audrey II. Audrey II looks like a towering, blood-eating Venus flytrap plant, even mimicking the jaw-like, snapping pod of real carnivorous plants. But while Venus flytraps consume insects, Audrey II feeds on humans. 

Thankfully, people-eating plants are fictional, says Kenny Coogan, the owner of Carnivorous Plants by Kenny Coogan, a well-known nursery in North Carolina’s Piedmont Triad area. 

On the other hand, plants that trap and digest bugs and, on occasion, small rodents are not only real, but actually quite diverse. Popular Science turned to Coogan to find out why some plants are carnivorous, while others simply soak up their necessary nutrients straight from the soil. We also asked Coogan to dig into all the details behind what makes these plants deadly, at least to birds and other small animals.

What are carnivorous plants?

Carnivorous plants are predatory flowering plants that attract, catch, and absorb animals for their nutrients. They’re both autotrophs, which are organisms that make their own food using light or chemical energy, and heterotrophs. This means that they also have to eat animal prey to survive. 

“Carnivorous plants photosynthesize,” says Coogan. “They can use the sun to convert carbon dioxide and water into sugar,” he says, for substance. “They’re just getting some extra minerals or nutrients from the bugs or the organisms that they eat.”

Meat-eating plants exist on every continent save Antarctica, and grow in sun-filled places with extremely poor, acidic, and nutrient-free soil. For instance, the bogs, swamps, and marshes of North Carolina and Florida, with their unique combination of sunlight and wetlands, allow these uniquely adapted flora to thrive. This includes Venus flytraps, which are native only to the U.S. Carolinas, and Tracy’s sundew, with its long, thread-like leaves that grow in spirals. It’s often seen blooming alongside carnivorous pitcher plants in the Florida Panhandle. 

“Carnivory is primarily an adaptation for plants to get nutrients in low nutrient environments,” says Coogan. Carnivorous plants feed on insects to obtain the nitrogen, phosphorus, and other organic nutrients they need to survive, but are unable to absorb from the soil. 

This isn’t to say that all plants that grow within poor-soil wetlands are carnivores. Take wiregrass, which is quite prominent in the southeast. “It has really heavy root systems,” says Coogan, which have formed a symbiotic or long-term relationship with mycorrhizal fungi. These fungi attach to the wiregrass roots and help them form nutrients from the region’s poor, sandy soils. 

“There’s only a certain number of niches to be filled in an ecosystem, so some plants went one way,” meaning they became carnivores, “and then some plants went the other way.”

How did carnivorous plants evolve?

There are an estimated 800 to 860 species of carnivorous plants worldwide, with new species constantly being discovered. In fact, in the more than 140 million years that flowering plants have been around, carnivory has evolved independently at least a dozen times. 

Carnivory is not inherited from a single meat-eating plant ancestor. Instead, carnivorous plants’ highly adapted leaf structures, which include sticky traps, snap traps, and pitfall traps for catching insects, have evolved and diversified more recently, largely between eight and 72 million years ago.

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Carnivorous plants are a classic example of convergent evolution. This means that unrelated lineages have all developed similar traits separate from one another to adapt to their sunny, waterlogged, and nutrient-poor environments. 

For example, “There are many different kinds of pitcher plants,” carnivorous plants that have hollowed-out pitcher-shaped leaves that act as pitfalls, says Coogan, and they’re completely unrelated. You’ve got low-growing Australian pitcher plants, which are evolutionarily closer to roses, beans, and broccoli, Asian pitcher plants that hang from tropical vines, and upright, trumpet-like North American pitcher plants. Despite their completely different DNA, they’ve all evolved the exact same, tube-shaped “pitfall trap,” says Coogan, to catch and digest insects. 

Through convergent evolution, unrelated carnivorous plants like Venus flytraps, sundews, and pitcher plants have also independently repurposed ancient self-defense genes into ingenious digestive tools. While noncarnivorous plants have long used enzymes, called chitinases, to fight off fungal infections, carnivorous plants do the opposite. They use chitinases to break down the tough, chitin-rich exoskeletons of trapped insects. This then allows them to absorb vital nutrients like nitrogen and phosphorus, transforming what were originally passive, protective enzymes into active weaponry.

Are carnivorous plants harmful to larger organisms? 

“I would say ‘no,’’ says Coogan. Almost all carnivorous plants feed exclusively on small insects like flies, mosquitoes, and spiders. 

While there are some, like giant pitcher plants, that grow large enough to trap and digest small animals like rats and shrews, “the relationship is more mutualistic,” meaning both species benefit from each other. 

Basically giant pitcher plant species produce a sweet, aromatic nectar on the underside of their pitcher lids that attracts small mammals. These mammals “sit on the lid of the pitcher plant to drink the exudate, which is a thick nectar-like substance,” says Coogan. 

They’ll often defecate into the plant while feeding, and the giant pitcher absorbs nutrient-rich nitrogen and phosphorus directly from the droppings. It’s a win-win for both parties. “And one of many examples of mutualism in carnivorous plants.” If a small animal accidently falls in, the pitcher plant will then use its acidic digestive enzymes to consume it. 

Some incredible carnivorous plants

Coogan’s favorite carnivorous plants run the gamut from small, semi-aquatic Genlisea, commonly known as corkscrew plants, to bladderwort, tiny, bladder-shaped traps that catch small, aquatic creatures and often resemble orchids. 

“There are over 200 species of them,” he says, “and they come in three different habitat types. You have fully aquatic bladderwort that are floating in water. You have terrestrial ones that live in kind of soggy soils, and then you also have epiphytic ones that are living in trees and in moss.” They all use ultra-quick, vacuum-driven suction traps to capture prey. 

In fact, bladderwort is one of the fastest predatory plants on Earth, and can suck in its prey in less than one millisecond. “The real reason I like them is because they are proliferous, meaning they flower en masse.”

Also popular: butterwarts. “Especially the Mexican butterworts or Pinguicula,” says Coogan. “The reason is that they’re excellent house plants. They look like succulents, but their leaves are sticky and they eat fruit flies and fungus gnats.” They act as a natural form of pest control.

What’s the largest carnivorous plant? 

The world’s largest carnivorous plant by trap volume is the giant montane pitcher plant. It’s endemic to Malaysian Borneo and features massive urn-shaped traps that can grow up to 16 inches tall and eight inches wide. While lizards, frogs, and birds do occasionally fall victim to the plant’s digestive enzymes and acids, most wildlife is in the clear. 

Humans can also count themselves safe, Audrey II aside. 

In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.

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Ecuador’s Galapagos Islands are home to an incredible array of wildlife. Amid landscapes of black lava fields, scattered prickly pear cacti, lush highlands, and green mangrove fringes, you’ll spot lumbering land iguanas in striking shades of yellow, orange, and red, comical blue-footed boobies, and some of the pinkest flamingos around. But it turns out that these magnificent creatures aren’t born with their vibrant hues. They actually have to work for them! 

To find out why some wildlife changes color according to their diets, and what these various tones and tints mean for survival, Popular Science turned to Jorge Alex Gutierrez Guerrero, an expedition leader on the Galapagos Islands’ Yacht Isabela II. Guerrero says it all comes down to naturally occurring pigments that play a major role in an animal’s immune system. They can even change the color of your skin!

What are carotenoids? 

The colorful displays of Galapagos wildlife, including the bright cyan feet of blue-footed boobies and the impressive red throat pouch of magnificent frigatebirds that they inflate during courtship, are a direct result of their diet. Specifically, they result from the digestion of nature’s own punchy dyes known as carotenoids. 

“Basically, carotenoids are natural pigments produced by plants, algae, and phytoplankton,” says Gutierrez. These organic chemical compounds play a vital role in nature. They help capture light for photosynthesis, which is how plants use sunlight to make their own food. They act as powerful antioxidants that can protect cells from damage. And they provide the vibrant colors that many animals, birds, and fish need to survive. 

For instance, flamingos gradually lose their red pigmentation when their diet lacks carotenoids. According to Gutierrez, this is a perfect example of the “direct relationship between dietary carotenoids and coloration.” 

How Galapagos animals get their colors

Wildlife in the Galapagos gets carotenoids primarily through their diets, since these are pigments that they can’t produce naturally. The archipelago’s land iguanas eat cactus flowers and leaves to obtain carotenoids, while blue-footed boobies consume fresh fish like sardines and anchovies to acquire them. Pink flamingos get their fill of carotenoids through algae and brine shrimp. 

Once the wildlife digests and metabolizes these natural pigments, the colors of carotenoids, which primarily produce shades of red, orange, and yellow, begin to show in everything from skin and shells to feet and feathers. In many cases, the more brilliant the shades, the healthier the creature. While carotenoids don’t naturally create the color blue, the archipelago’s iconic blue-footed boobies get their turquoise feet from a mix of yellow carotenoid pigments and the collagen structure of their skin. 

How other animals get their vibrant hues

Examples of the power of carotenoids even exist in our own backyards. 

The sunny yellow coloring of an American goldfinch is a direct result of its carotenoid-rich diet of summer weeds and sunflowers, while northern cardinals get their brilliant red hue through carotenoid-heavy foods such as honeysuckle, hackberries, and seeds.

Why do animals need carotenoids? 

Carotenoids aren’t a core nutritional necessity. However, they are an important source of vitamin A, a key component in reproductive health, good vision, and a strong immune system. 

While the bulk of birds and animals get carotenoids through their diets, a few rare invertebrates, like spider mites and gall gnats, can create their own carotenoids. They do so through a rare genetic accident, likely caused by a virus or parasite. An ancestor of the spider mite and an ancestor of the gall gnat had close encounters with ancient fungi, causing a horizontal gene transfer. Essentially, horizontal gene transfer is the transmission of DNA between different organisms—and, in this case, species.

Every animal processes these pigments slightly differently. For some animals, carotenoids completely change the color of their features. Others simply absorb carotenoids without changing color at all. 

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But all animals use carotenoids to fight off disease, such as boosting immune cells to destroy any harmful bacteria. Only healthy wildlife can spare excess carotenoids for bright skin, beaks, or feathers. So the more vibrantly hued birds, reptiles, and fish are, the healthier their immune system. They have enough carotenoids to spare for flashy colors.

For instance, blue-footed boobies with electric, turquoise-blue feet tend to be healthiest. In fact, boobies that go without food for a couple of days can end up with dull-colored feet. When animals get sick, they also lose their hue. First, their bodies divert carotenoids away from exterior features, like skin and feathers, and use them for fighting illness. Second, absorbing nutrients such as carotenoids becomes more difficult. Without carotenoids, an animal’s bright pigments will quickly fade. 

Bright colors also come in handy during mating rituals 

Carotenoids also play vital roles in mating rituals. When it comes to blue-footed boobies, “It’s very important for a female to find a male with the brightest blue feet, because she is choosing the best provider” for her offspring, says Gutierrez. 

It’s a feature that these marine birds show off frequently in their oh-so-quirky mating dance, which includes an elaborate high-step strut. The bluer the feet, the more attractive males appear to their female counterparts. 

What’s more, a famous 2006 scientific study on blue-footed boobies showed that females lay smaller eggs for males with duller feet. Basically, a female will put in less reproductive investment if her male isn’t up to par. 

Why are animals in the Galapagos so colorful? 

“Carotenoids are prominent all over the world,” says Gutierrez. “But they’re especially visible among wildlife in the Galapagos, because it’s a limited environment where the ecosystems are well-marked.” What Gutierrez means is that the archipelago is so geographically isolated and far from the coast of Ecuador, many species—like marine iguanas—have nowhere else to go. Even within the Galapagos, a large percentage of wildlife stick closely to their specific islands. 

Another reason the animals here are so colorful? Because an overall lack of predators has allowed the wildlife to evolve without needing dull or camouflage coats to protect them. 

Most of the archipelago’s carotenoids come from the ocean, or in the case of land iguanas and yellow-beaked Darwin’s finches, through cactus nectar and pollen. 

Further afield, the iconic pink-orange flesh of Pacific Northwest salmon is a direct result of their carotenoid-rich diet—in their case, chowing down on krill and small shrimp. Roseate spoonbills, found across the mangrove swamps, mudflats, and wetlands of the U.S. Gulf Coast, get their rosy pink sheen from dining on crustaceans, crabs, and crayfish. 

Can carotenoids make people change colors?

As to whether eating carotenoid-rich foods will change a person’s skin color, it’s definitely possible. 

The best known example comes from consuming carrots. These vegetables are loaded with a red-orange carotenoid called beta-carotene, which our bodies convert into vitamin A. 

But when we consume more beta-carotene than we need, the excess pigment starts circulating in our bloodstream and leads to a yellow or orange glow. “It’s mostly visible in your palms,” says Gutierrez. 

Still, he says, don’t worry if you have a penchant for sardines and anchovies—the main diet of blue-footed boobies. Since humans process and metabolize these compounds differently, “you’re not going to turn blue, too.”

In Ask Us Anything, Popular Science answers your most outlandish, mind-burning questions, from the everyday things you’ve always wondered to the bizarre things you never thought to ask. Have something you’ve always wanted to know? Ask us.

The post Why are some animals so colorful? Blame this pigment. appeared first on Popular Science.