A Student Discovered The First Meat-Eating Plant In North America – And It Feasts On Salamanders

Image: M. Alex Smith

It’s the summer of 2017, and a bunch of undergrads are visiting a Canadian park. Something catches one of the students’ eye when he looks into one of the pitcher plants that are common there. He has stumbled on a new discovery which will capture the imagination of scientists and public alike.

Image: Facebook/Teskey Baldwin

That student, Teskey Baldwin, then shares what he has seen with his University of Guelph biology professor, M. Alex Smith. At which point, Smith’s excitement is palpable. Indeed, he has what he will describe in 2019 as a “WTF moment” to U.K. newspaper The Guardian.” And that’s because he’s witnessing something that many did not believe possible.

Image: YouTube/National Geographic

Indeed, Baldwin found something inside the plant that no one anticipated. The vegetation is a species known commonly as “turtle socks” because of its looks. More usually, it goes by “purple pitcher plant,” because of the bell-shaped receptacle that it catches insects and other small invertebrates in. It also, however, carries the more imposing Latin name of Sarracenia purpurea purpurea.

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Image: M. Alex Smith

The discovery prompts scientists, including Smith, Baldwin and others from Guelph and Toronto universities, into research that will lead to a paper two years later. And when word gets out, the world turns out to be just as interested. Stories about Baldwin’s find spread across the print media, not just in Canada, but all around the world.

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The purple pitcher plant can be discovered in all sorts of places in the east of North America. Its range stretches from Florida’s Gulf Coast right up to Canada’s Nova Scotia. And you’ll find them across to the west as far as the Rockies. It’s the most commonly found plant of its type, and the sole Sarracenia that will grow in chillier climates.

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Meat-eating plants aren’t actually that rare globally, with close to 600 different varieties on the planet. While some also have pitchers, others deploy traps. Still more, such as the sundews, covering close to 200 species, work like living flypaper, capturing insects with their stickiness. Meanwhile, the bladderwort, as its name suggests, sucks unwary invertebrates into a bladder that they can never escape from.

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The pitcher plant family, Sarraceniaceae, and particularly the type that surprised Baldwin, the purple pitcher, has caught the attention of naturalists for a couple of centuries. And meat-eating vegetation even attracted none other than Charles Darwin, who studied a type of sundew in England in 1860. Indeed, he later wrote, “I care more about Drosera than the origin of all the species in the world.”

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Darwin didn’t stop at the sundew, though, as he went on to study other types of carnivorous vegetation as well. Finally, he wrote a book about them in 1875, called Insectivorous Plants. The great scientist adored them and would dub the Venus flytrap, which he hugely admired, “one of the most wonderful [plants] in the world.”

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Despite Darwin’s great reputation, however, some people couldn’t believe that it was possible for plants to behave in the ways that he described. One botanist would even describe the author’s work on carnivorous plants as “scientific garbage.” This statement put that particular dissenter in the tradition of Carl Linnaeus. Indeed, the famed Swedish biologist once described meat-eating plants as “against the order of nature.”

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The plant found in Canada is just one type of pitcher plant, a member of the “New World” group, which also includes cobra plants. They grow on the ground and have specialized leaves to capture prey in. “Old World” pitchers, however, in the genus Nepenthes, differ. Indeed, some are climbers and they have developed pitchers using only part of a leaf, rather than the whole thing.

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Usually, the purple pitcher plant eats nothing but invertebrates. They’re not too fussy about what type – any wasp, fly or beetle that lands in a Sarracenia purpurea trap will find itself eaten. Indeed, scientists found representatives of more than 40 insect families in pitchers in Ontario and around 115 in North Carolina.

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So how does it all work? Well, the leaves of the plant are shaped to catch and keep rainwater, which it fills with enzymes. Captured prey are then digested by those enzymes, but, interestingly, the pitcher plant also houses lots of small organisms that help dissolve food. Indeed, the bowl contains a huge array of insect larvae, bacteria and mites, among others.

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Many of those small beings can only live in the pitcher. The larger beasts grind the prey into pieces, and the littler ones eat the bits. This in turn provides nutrients for the plant. As The University of Vermont’s Nicholas Gotelli told National Geographic magazine in 2010, “Having the animals creates a processing chain that speeds up all the reactions. And then the plant dumps oxygen back into the pitcher for the insects. It’s a tight feedback loop.”

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However, even though it’s possible that eating meat is good for the plants – when fed more, they grow bigger – it doesn’t work the way it does for humans. If you eat meat, you extract carbon and fat from it to use in muscles and for energy. But the carnivorous plants use the chemicals that they draw from their food – such things as phosphorus and nitrogen – to build enzymes that harvest light. So they gain energy in the same way as all vegetation.

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So it’s likely that when Baldwin peeked into a pitcher plant in 2017, he expected to see insects dissolving in the liquid. He was in Algonquin Provincial Park as part of a course set up by University of Guelph. The park originated in 1893, making it Canada’s longest-established public park. And the wildlife there has been heavily studied, which is not a surprise, given the park’s proximity to Ontario’s big cities.

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But no researcher had previously seen what Baldwin encountered. It turned out that the pitcher plant he was examining had taken on a far bigger meal than usual. In fact, this Sarracenia was chowing down on a salamander. And when the undergrad’s professor took a look, he, too, was stunned. It seems that this was indeed an astonishing find.

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Although it was stunning to find this behavior in northern pitcher plants, it’s not unheard of for carnivorous plants. The tropical Nepenthes will, in fact, also devour animals. Researchers who have studied these plants have found that they actually have schemes for hunting small beasts such as birds and rats, much as vertebrates do.

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With that in mind, Japanese ecologist Kazuki Tagawa told National Geographic magazine in 2019 that finding animals such as rats and frogs in the plants was, in his opinion, rather unusual. He said that they were “thought to be a rare prey trapped accidentally.” So Smith, shocked by what Baldwin had discovered, talked about it with the University of Toronto’s Peter Moldowan.

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Moldowan operated as an expert in salamanders at the park, and hearing about the find piqued his interest, so he went to look for himself. And as he told National Geographic magazine in 2019, “The very first plant that I kneeled down and peered into had captured a salamander and it was alive and swimming.” He looked further and found that one in five of the pitchers contained salamanders.

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Smith would later tell The Guardian that Moldowan’s find had been “the second WTF moment.” The professor then went on to share his reflections on what the salamander expert had seen. He said, “This crazy discovery of previously unknown carnivory of a plant upon a vertebrate happened in a relatively well-studied area on relatively well-studied plants and animals!”

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Consequently, a research effort kicked into gear. Scientists from the universities of Toronto and Guelph looked into plants in their hundreds in four separate efforts, focusing their work on one particular pond. They would go on to report the outcome of their study in an article for the journal Ecology.

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In that article, the researchers said, “In total, eight individual salamanders were found trapped in pitcher plants during survey efforts in 2017 and an additional 35 individuals were recorded with increasing survey effort in 2018.” These figures represent nearly a fifth of the plants the team looked at. So, it seemed that the salamanders might form a part of the pitcher’s diet.

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Moldowan then looked at the plants over the end of summer and the start of fall. And he found lots of trapped amphibians. It’s entirely possible, however, that this isn’t a coincidence. In fact, it’s the same time of year that salamanders that have recently completed their metamorphosis, part of their development into adults, emerge from a lake close to the location of the survey.

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It seems that the reason no one had previously known the pitchers to eat salamanders lies in the timing. Usually, the plants are studied a little earlier in the year. But now scientists were looking during the period in which the young salamanders become land-based. And it seemed that the carnivorous greenery was gobbling them up when they did.

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These newly formed salamanders, then, make a great snack for the plants, since they are small enough to fit into their trap. That’s because the juveniles are only about as long as one of your fingers. The species discovered in the pitchers, Ambystoma maculatum, or the spotted salamander, is named for the distinctive yellow splotches on its body.

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Once fully grown, though, the salamanders are much bigger, around eight inches long. They like to live in forests and in hilly areas near water. When it’s breeding time, they head to places that are not always underwater and consequently don’t house any fish. When not procreating, they prefer darker, gloomier habitats, such as the underside of logs.

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The salamander’s breeding season is early in the springtime, when ponds might even still be frozen. Females will deposit hundreds of eggs in a clump stuck to underwater greenery. A couple of months later, tiny larvae come out and swim into the water, developing over the next couple of months until they are ready to leave the pond.

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So there may actually only be a small window in which the salamanders can be spotted in the pitchers, between coming out of the water and disappearing into the woodland. And there may be another factor in explaining why they hadn’t been seen there before Baldwin’s discovery. Indeed, the young amphibians tend to swiftly decay in the gooey liquid of the traps.

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This timing has suggested to scientists an explanation for why the salamanders end up in the pitchers. In this conception, the amphibians, appearing freshly on land, find the pitchers appeal as places to hide. However, they aren’t short of places to shelter on the pond verge, so the researchers consider this explanation unlikely.

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Instead, the scientists consider it more probable that the baby salamanders had simply followed insects into the pitchers. After all, the amphibians are themselves carnivorous, both as larvae and as adults. And they enjoy a diet that includes the kinds of creatures that are attracted to the plants’ repositories of nectar.

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However, the scientists also thought it was possible that the salamanders sometimes just fall in the traps by accident. How? This can happen if the pitcher is level with the peat moss that the plants grow in. From time to time, though, the baby amphibians are able to escape, perhaps helped by a downpour. But if they don’t, the outlook is grim.

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Image: M. Alex Smith via Science News

The researchers also found that the amphibians could survive in the pitcher for around three weeks. The team wasn’t sure what caused the salamanders to die, however, with suggestions ranging from overheating to changes in the acidity level of the pitchers’ water. In addition, infections that the babies, without a fully developed immune system, may be prone to could also cause death. In the end, though, they might just run out of food.

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Now the researchers are looking into these questions, hoping to figure out how the amphibians end up within the pitcher plant’s deadly embrace. What’s certain, though, is that when they do die, their bodies quickly disappear. Indeed, the pitchers take no more than a fortnight to digest them. This suggests that the plants may produce a chemical that actually hastens the salamander’s end.

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Given their size, though, the salamanders may represent sizeable snacks for the plants. After all, there isn’t much to eat in the boggy lands that the plants inhabit. This led the team to more interesting questions about this find. Do the pitchers even eat the amphibians? Or is the supply of nutrients simply too much?

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While it’s clear that the plants gain size when they eat bugs, it’s not certain that eating salamanders is even good for the pitchers. Indeed, it may be that a big animal could decay and rot before they’ve finished eating it. And this could bring about their own untimely end.

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However, it might be that the salamanders keep the pitcher plants going over winter, which can start early in Ontario. Moldowan told National Geographic magazine about their potential as a supply of cold-weather feed. He said, “Compared to any sort of invertebrate life that these plants might capture, salamanders offer hundreds to thousands of times more in nutrient inputs ‒ things like nitrogen and phosphorus.”

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Whether it turns out that eating salamanders is good for plants or not, it’s definitely bad for the junior amphibians. As many as one in 20 of the babies coming out of the pond might find themselves as plant food. This level of threat would mark the pitchers down as one of the bigger predators the salamanders face.

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Indeed, it seems that there are plenty of mysteries around the salamander-munching plants. Smith shared a few of them with The Guardian in 2019. He said, “Are plants a significant form of mortality for the salamanders? Are the salamanders a significant form of nutrition for the plants? Are the salamanders, in fact, not a good thing for the plants?”

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Meanwhile, Moldowan intends to find some answers. He’ll be measuring the pitcher plants to see whether they grow bigger after capturing a salamander. And he’s curious whether other beasts also fall into the plants’ trap. He hadn’t yet seen a toad or frog in trouble, but that might just be an outcome of looking at the wrong time. As he told National Geographic magazine, “This year, I’ll more specifically try to address that by sampling over a wider period of time.”

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And Moldowan expects his searches to turn up a lot of new information. He said, “This is probably a much more widespread phenomenon than we currently recognize.” Which leads Smith to share with The Guardian a dream that he has. He imagines the day when the park’s promotional material warns kids to stay on the boardwalk because “here be plants that eat vertebrates!”

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