Meat-eating pitcher plants feast on baby salamanders | Science News for Students

Meat-eating pitcher plants feast on baby salamanders

Once trapped in the plants, the young amphibians can take more than two weeks to die
Sep 27, 2019 — 6:45 am EST
a photo of a baby salamander trapped in a pitcher plant

Once trapped, baby salamanders rarely escape the northern pitcher plant. The inside of the plant’s leaves has a slippery coating that makes it hard for the amphibians to climb out.

Patrick D. Moldowan

Carnivorous plants in Ontario’s Algonquin Park don’t eat just bugs. These Canadian pitcher plants also snack on young salamanders.

Until now, scientists hadn’t thought that meat-eating plants in North America ate vertebrates. Those are animals with a brain, two eyes and a backbone. Vertebrates includes amphibians, reptiles, birds, mammals and fish.

Pitcher plants in Asia do eat vertebrates. Some make a meal of small birds and mice. But those in Canada and the United States feed mostly on insects and spiders. Those creatures fall into the plant’s bell-shaped leaves and then gradually decompose in the small pools of rainwater that these plants collect.

a photo of a cluster of pitcher plants
Pitcher plants grow in bogs, where the soil has few nutrients. Scientists think the plants evolved to eat insects, spiders — and salamanders — to gain necessary nutrients, such as nitrogen.
P. D. Moldowan

Scientists had recorded seeing the odd baby salamander trapped in a northern pitcher plant. Until now, however, no one had looked carefully enough to realize these plants might regularly dine on them. That’s probably because most biologists study pitcher plants in the spring and early summer, before it starts to get too cold, says Patrick Moldowan. He’s a graduate student at the University of Toronto in Canada.

He headed a team that went into the field to study these plants in late summer and early fall. It’s when young yellow spotted salamanders end their larval stage. They now begin crawling out of ponds and onto land.

One in every five pitcher plants in a small pond near the Algonquin Park Wildlife Research Centre contained a young salamander. Each was about two to three centimeters (0.8 to 1.2 inches) long. Moldowan and his team described their findings on June 5 in the journal Ecology

Caught while stalking lunch?

The pitcher plants here grow some 8 to 10 centimeters (about 3 to 4 inches) tall. Moldowan and his team think the salamanders may climb up the plant in search of tasty insects. If they’re not careful, young amphibians may slip on the waxy leaves. Few that fall into the pitcher’s collected rainwater make it out, he says. The insides of the leaves are just too slick.

a photo of Algonquin Park bog
This photo shows the Algonquin Park bog where Patrick Moldowan’s team surveyed pitcher plants. One in five of the plants held at least one baby salamander.
Alex Smith

“The first time I saw a trapped salamander, my heart went out to it,” recalls Moldowan. “It looked like it was struggling.” He thought about rescuing the salamander. Then he changed his mind. “It got caught fair and square,” he says. In ecology, it’s often eat or be eaten. And these guys were about to become lunch — and dinner and breakfast — for quite a while.

Moldowan and his team found trapped salamanders took anywhere from three to 19 days to die. They are not certain how the salamanders die, but they may starve or succumb to exhaustion as they struggle to escape. Or they might get eaten alive, Moldowan says. Pitcher plants produce enzymes. These are molecules made by living things to speed up chemical reactions. Some enzymes help plants break down a meal into digestible components.

“Another theory is equally grisly,” Moldowan admits. The young salamanders “may essentially get cooked.” There is very little water inside the plant, so “standing in the sun, it will heat up.”

A rotten discovery

In the summer of 2017, Teskey Baldwin, a student at Canada’s University of Guelph, was studying whether pitcher plants near water capture more insects than those farther away. During his fieldwork, Baldwin spotted a salamander rotting in a pitcher plant. He scooped it into a jar.

That evening, over dinner at the Algonquin Wildlife Research Station, he showed the jar to Moldowan.

This video shows two young Spotted Salamanders (Ambystoma maculatum) trapped in the pitcher of a Northern Pitcher Plant (Sarracenia purpurea). It’s a carnivorous plant that lives in nutrient-poor bogs. Salamanders for supper? Yes!
Algonquin Wildlife Research Station/YouTube

“It was hard to tell what it was because it was pretty decomposed,” Moldowan recalls. But then Baldwin found other salamanders in pitcher plants, and these were immediately recognizable.

Last year, Moldowan decided to take a closer look. That’s when he saw how many of the amphibians were losing their lives this way. He now thinks salamanders may be an important source of nitrogen for the plants. Nitrogen is an essential nutrient for all living things. But the bogs and ponds where pitcher plants grow have very little of this nutrient.

“When they catch salamanders, it’s close to the end of the growing season,” says Moldowan. “Our hunch is that the plants bank the nutrient pulse for the next year. It’s like nutritional money in the bank.”

Unanswered questions abound

Like any piece of science, this study leads to new questions, says Stephen Heard. A biologist, he studies plant-insect interactions in eastern Canada at the University of New Brunswick in Fredericton.

“I wonder how much nutrition the plants are actually getting from the captured salamanders,” he says. “Does a plant that's lucky enough to catch a salamander grow more quickly or make more seeds than a less lucky plant?”

Heard also wonders about the salamanders. Are enough getting caught in pitcher plants to drive the salamander population down?

These are all good questions, says Moldowan. And he hopes to answer them over the next few years. “It’s not a lion chasing down a gazelle on the Serengeti,” he says. Still, he notes, salamander-eating plants is “a pretty cool predator-prey interaction.”

a photo of a baby yellow spotted salamander
This baby yellow spotted salamander has so far avoided being trapped in a pitcher plant. Researchers wonder if enough salamanders are being eaten by pitcher plants to affect their population.
P. D. Moldowan

Power Words

(more about Power Words)

amphibians     A group of animals that includes frogs, salamanders and caecilians. Amphibians have backbones and can breathe through their skin. Unlike reptiles, birds and mammals, unborn or unhatched amphibians do not develop in a special protective sac called an amniotic sac.

biologist     A scientist involved in the study of living things.

bog     A type of wetland that forms peat from the accumulation of dead plant material — often mosses.

bug     The slang term for an insect. Sometimes it’s even used to refer to a germ. (in computing) Slang term for a glitch in computer code, the instructions that direct the operations of a computer.

carnivorous plant     A plant that trap animals, usually insects, as food.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemical reaction     A process that involves the rearrangement of the molecules or structure of a substance, as opposed to a change in physical form (as from a solid to a gas).

component     Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).

ecology      A branch of biology that deals with the relations of organisms to one another and to their physical surroundings. A scientist who works in this field is called an ecologist.

enzymes     Molecules made by living things to speed up chemical reactions.

field     A term to describe a real-world environment in which some research is conducted, such as at sea, in a forest, on a mountaintop or on a city street. It is the opposite of an artificial setting, such as a research laboratory.

graduate student     Someone working toward an advanced degree by taking classes and performing research. This work is done after the student has already graduated from college (usually with a four-year degree).

insect     A type of arthropod that as an adult will have six segmented legs and three body parts: a head, thorax and abdomen. There are hundreds of thousands of insects, which include bees, beetles, flies and moths.

mammal     A warm-blooded animal distinguished by the possession of hair or fur, the secretion of milk by females for feeding their young, and (typically) the bearing of live young.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2); water is made of two hydrogen atoms and one oxygen atom (H2O).

nitrogen     A colorless, odorless and nonreactive gaseous element that forms about 78 percent of Earth's atmosphere. Its scientific symbol is N. Nitrogen is released in the form of nitrogen oxides as fossil fuels burn. It comes in two stable forms. Both have 14 protons in the nucleus. But one has 14 neutrons in that nucleus; the other has 15. For that difference, they are known, respectively, as nitrogen-14 and nitrogen-15 (or 14N and 15N).

nutrient     A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

nutrition     (adj. nutritious) The healthful components (nutrients) in the diet — such as proteins, fats, vitamins and minerals — that the body uses to grow and to fuel its processes. A scientist who works in this field is known as a nutritionist.

pitcher plant     A carnivorous plant that traps bugs in traps filled with fluid and shaped like pitchers.

population     (in biology) A group of individuals from the same species that lives in the same area.

predator     (adjective: predatory) A creature that preys on other animals for most or all of its food.

prey     (n.) Animal species eaten by others. (v.) To attack and eat another species.

spider     A type of arthropod with four pairs of legs that usually spin threads of silk that they can use to create webs or other structures.

vertebrate     The group of animals with a brain, two eyes, and a stiff nerve cord or backbone running down the back. This group includes amphibians, reptiles, birds, mammals and most fish.

Citation

Journal: P. Moldowan et al. Nature's pitfall trap: Salamanders as rich prey for carnivorous plants in a nutrient‐poor northern bog ecosystem. Ecology. Published online June 5, 2019. doi: 10.1002/ecy.2770.