Insectivorous Plants That Eat Salamanders

In the western peat-bog forests of Algonquin Provincial Park in Ontario, Canada, researchers documented an unusual ecological interaction. The region consists of acidic wetlands that lack fish but support relatively dense amphibian communities. Among the vegetation growing in this environment is a carnivorous plant, the purple pitcher plant, Sarracenia purpurea. Carnivorous plants are typically known for capturing small arthropods and extracting nutrients such as nitrogen and phosphorus from them. However, in this particular ecosystem the purple pitcher plant has been found to capture and consume the spotted salamander, Ambystoma maculatum.

During an initial survey, researchers examined 144 pitcher plants and unexpectedly discovered eight recently metamorphosed spotted salamanders inside the pitchers. Six of these individuals were still alive and swimming within the water collected in the plant's trap. When the survey was expanded the following year, a total of 35 metamorphosed salamanders were found trapped in pitcher plants, indicating that this phenomenon was not merely accidental. Field observations showed that nearly 20% of the surveyed pitcher plants had captured salamanders, suggesting a consistent ecological interaction between the plant and amphibians in this region.

The captured salamanders represent a particularly rich nutrient source for the plant. On average, a recently metamorphosed spotted salamander has a dry mass of about 155 milligrams, of which approximately 11.9% consists of nitrogen. For plants growing in nutrient-poor soils such as bogs, this represents a highly valuable nutritional resource.

Ambystoma maculatum trapped inside a pitcher of Sarracenia purpurea（Courtesy of M. Alex Smith）

How do these salamanders end up inside the pitchers of Sarracenia purpurea? Researchers have proposed several possible explanations.

First, the leaves of pitcher plants sometimes lie partially against the ground. Salamanders moving across the mossy surface may accidentally fall into the opening while searching for shelter or simply passing by.

Second, salamanders that enter the pitchers appear to dive downward and hide near the bottom, especially when they sense a threat. This behavior suggests that the pitcher may sometimes be mistaken for a temporary refuge.

Third, pitcher plants possess nectar glands that attract numerous insects. Salamanders may approach the pitchers to hunt these insects and inadvertently fall into the trap while foraging.

Once inside the pitcher, some salamanders are able to escape, but others remain trapped. Observations indicate that trapped individuals may survive for as little as three days or as long as nineteen days before dying within the pitcher fluid. The variation in survival time likely reflects differences among individuals, including their physiological tolerance to the acidic digestive fluid, whether they had recently fed before falling in, or whether weakened individuals become infected by microorganisms living within the pitcher fluid.

Although carnivorous plants occasionally capture vertebrates, it remains relatively rare for vertebrate prey to be a regular component of their diet. In this bog ecosystem, however, salamanders appear frequently enough that they may play a meaningful role in the nutrition of the pitcher plants. At the same time, the plants themselves may represent a non-trivial source of mortality for newly metamorphosed salamanders dispersing into the surrounding forest.

This interaction reveals an unexpected ecological relationship: in certain nutrient-poor wetlands, a carnivorous plant and an amphibian may become linked through a predator–prey interaction that benefits the plant while shaping the survival of the salamander population.

Video:

https://www.youtube.com/watch?v=pbNFgZS3dt0

Author: Shui-Ye You

Reference:

Moldowan PD et al. (2019). Nature's pitfall trap: salamanders as rich prey for carnivorous plants in a nutrient-poor northern bog ecosystem. Ecology.