I find the urge to explore bogs and boggy habitats difficult to resist. Other people avoid them, which gives me space to be alone. They’re mucky, which is often a fun and challenging substrate underfoot. They contain unique species, which I find fascinating. They are full of life. And they offer surprises.
On an unseasonably warm late October day, I found myself poking around the edges of Little Messer Pond, an approximately 27-acre pond in Katahdin Woods and Waters National Monument, Maine.
While exploring the pond’s northern flank, on a shelf of sphagnum peat that cups the pond’s shore, I found several purple pitcher plants (Sarracenia purpurea), one of the most iconic bog species in this area. The purple pitcher lives an uncommon, carnivorous lifestyle for a photosynthesizing organism. Pitcher plants supplement their growth by capturing small animal prey, typically insects. Unlike Venus fly-traps, however, which ensnare prey using a trigger-like mechanism, pitcher plants use a passive, gravity-driven process. Their leaves form bell or cone-shaped bowls that fill with rainwater. The top of the each leaf has a flaring lip lined with nectar glands to attract insects. If a hapless insect falls inside, downward pointing hairs resist its escape attempts.
Pitcher plants can’t move, so they have unsurprisingly indiscriminate tastes. To cite just one example, a study from Newfoundland documented 12 insect orders serving as prey in pitcher plants. Prey eventually drowns in the pitcher’s water where enzymes as well as inquilines (microorganisms adapted to live in the pitchers such as midge larvae, nematodes, bacteria, protozoa, and rotifers among others) break down the trapped prey, releasing nitrogen and phosphorus for the plant. Purple pitcher plants, in particular, seem to be particularly rich in inquilines, hosting at least 165 different species across its range. Pitchers are habitats of their own making and their adaptations allow them to live in nutrient poor soils where competition from tall plants in minimal.
Looking at the pitchers on the edge of Little Messer, I found ants, beetles, flies, dragonflies, various bits of unidentified insects, and a sludge of the leftovers in their bowls.
They’d eat me if I were small enough.
None of the prey was unusual or unexpected until I stumbled upon a curious sight—a spotted salamander inside a pitcher.
I was taken aback by the sight. I had never seen something like this before, and I remember exclaiming “What the?” even though I was alone. Was this a big payday for the plant or was the salamander only a temporary resident?
Small vertebrates are exceedingly scarce as a prey item for purple pitcher plants. In the scientific literature, I couldn’t find much documentation of it. A study from Massachusetts documented red-spotted newts as a food source for pitcher plants. A more recent study from an Ontario bog found that spotted salamanders are a potentially rich prey for pitcher plants. (One of the researchers leading that study described his sighting of a salamander in a pitcher plant felt like a “WTF moment” so I guess I wasn’t alone in my surprise.) In August 2017, researchers at that study site searched the contents of 144 pitcher plants. They found, as expected, mostly insects but also several recently metamorphosed spotted salamanders. In August 2018, they investigated 58 plants and found three spotted salamanders. The physical condition of the salamanders varied. Some were in an advanced state of decay while others were lively and were able to swim to the bottom of the pitcher when disturbed.
Plenty of uncertainty surrounds pitcher plants and the importance of small vertebrate prey to them like salamanders and newts. No one has yet tested what might attract a salamander into a pitcher since a salamander has to climb up to get into one. If the salamander can escape, then pitchers could be a refuge for salamanders who have recently emerged from the water onto the land. Perhaps salamanders are attracted to the pitcher by small insects visiting to feed on the plant’s nectaries. Their apparent capture could be random too, although, dead salamanders apparently break down quickly inside pitcher plants so maybe their true rate of capture is greater than anyone realizes.
I wonder if it might happen only in places with the right combination of habitats. Purple pitcher plants typically (but not exclusively) grow in nutrient poor bogs, places that don’t always support breeding populations of spotted salamanders. Adult spotted salamanders migrate en masse during spring to vernal pools where they breed. They may also use permanent ponds for reproduction as long as those don’t contain fish, which eat salamander eggs and larval salamanders. Newts, in contrast, breed in a greater variety of wetlands including ponds and lakes that contain fish.
At the Ontario study site, pitcher plants grow on bog islands in permanent and fish free ponds where spotted salamanders gather to breed every spring. This seems to provide a combination of habitats that increase the likelihood of pitcher plants capturing salamanders later in the year when the juvenile salamanders metamorphose and begin their terrestrial lives. Little Messer Pond, in contrast, is home to fish, snapping turtles, and presumably other salamander predators.
A salamander or newt, even a juvenile, is a significant catch for a pitcher plant. A newt of about 500 mg of dry mass contains about 5 mg of nitrogen, which is several orders of magnitude more than an ant, a pitcher’s most common prey. That’s enough nitrogen to increase the probability of the plant flowering the next summer. If the salamander I saw had indeed perished in the pitcher, maybe it’ll dignified in death by a marvelous pitcher plant flower next summer.
Pitcher plants are wonderfully adapted to secure nutrients and survive in habitats that most plants cannot tolerate. If they’re lucky enough to capture something as large and nutrient rich as a salamander, then their physical structure can hinder escape. Their acidic water (often lower than pH 4 by mid summer) can weaken salamanders through electrolyte imbalance. And, the water within them might contain compounds that inebriate or paralyze small prey.
The fate of the salamander that I found remains unknown. I returned a week later with the intention of relocating it, but I could not find it despite my best efforts. Although I can’t be sure, I think it is unlikely that I missed it since the boggy area with the pitcher plants isn’t large and the pitchers are easy to locate. If it were still alive, perhaps it fled to the bottom of the pitcher upon my approach. However, if it were still in the pitcher after seven days, then it should’ve been dead. Did it escape the trap that so many other victims of pitcher plants could not? I wish I knew the end of this story—a drama of uncertainty, survival, life, and death.