Have you ever wondered, how do carnivorous plants digest insects? One moment you see them, the next, they’re gone, rolled up in a trap or stuck in digestive fluids.

While most carnivorous plants take more time than we do to digest their meal, it’s not uncommon to find a little curiosity in the process.

In this article from HerbSpeak, you’ll learn everything you need to know about carnivorous plants and their mealtime habits, from how they digest their prey based on the trap type, to why they require carnivory in the first place.

How Do Carnivorous Plants Digest Their Prey?

Carnivorous plants’ nutrients do not come in the form of soil nutrients or whole food. Rather, the nutrients are absorbed once the food has been properly broken down by the enzymes in their ‘digestive tract.’

In carnivorous plants, however, the digestive “tract” is often more of a “pit” or chamber. These enzymes are there to help break down the body of the trapped prey into molecules that the plant can better absorb. (1)

In some cases, however, the plant doesn’t use enzymes at all to digest their prey. (2) Instead, they utilize a bacteria-based strategy for breaking down food into the nutrients they need, absorbing nutrients from the remains.

Unlike animals, plants cannot move, and therefore cannot physically hunt for their prey. Instead, they rely on their prey to come to them. The plant has evolved clever ways of tricking its prey into the traps. This linked HerbSpeak article on carnivorous plant types breaks down traps by their individual type.

Why Do Carnivorous Plants Eat Insects?

Carnivorous plants eat insects as a way to compensate for poor soil nutrients in washed out or sandy areas where they grow. Instead of succumbing to the malnutrition of a region, they evolved a new survival strategy.

Specifically, the native soil many carnivorous plants grow in is low in nitrogen, among other nutrients. It just so happens that a lot of insects have flesh that is high in nitrogen that the plants need to thrive. So, nature finds a way.

Why Are Insects Attracted to Carnivorous Plants?

To attract pollinators and prey, carnivorous plants must offer something in return – or at least, make the prey think that they have something to offer in return. A lot of flowers dupe pollinators into carrying their pollen to another flower by providing nectar.

Carnivorous plants have a variety of methods for attracting insects, and it often changes with the type of prey the plant is trying to attract. It could be a mix of flower-like visual appearances, volatile oils to give it a fragrant scent, or a sugary nectar.

In Borneo, there is a species of pitcher plant (Nepenthes spp.) that exudes a nutritious nectar. It exudes this nectar on the underside of the leaf that covers the pitcher. This is a perfect adaptation to the local tree shrews which come up and position themselves over the trap.

In most cases, the shrew is too big, or too dexterous to fall into the trap itself. Instead, this shrew licks the nectar off the plant and defecates into the pitcher like it was a toilet bowl. That defecation then feeds the pitcher plant.

Sometimes, the arrangement isn’t so mutualistic. (3) It is believed that insects are attracted to the Venus Flytrap because of fragrant oils, called volatile oils, that make it smell like food or flowers to nearby insects. Once the insects land on it, however, it snaps shut and traps the insect inside, secreting enzymes and slowly digesting the insect.

How Do Carnivorous Plants Absorb Nutrients?

In most cases, the plant contains a gland that secrets digestive acids and enzymes that can dissolve the captured prey. (4) This isn’t always the case, however. Carnivorous plants may also let the food rot, using bacteria to help them break down the food so it can absorb into the plant material.

Once broken down into small enough molecules, the nutrients become simpler and can more readily pass into the plant’s tissues, where it is taken up by plant’s cells.

This process is strikingly similar to how we digest food to break it down into smaller pieces (using both digestive acids and enzymes, as well as a microbiome of gut bacteria.) In our own digestive system, the nutrients absorb into our bodies after they become small enough, and we utilize those nutrients in the function and creation of cells throughout the body.

Do Carnivorous Plants Defecate?

No, carnivorous plants do not defecate in the traditional sense, but in many cases, the undigestible bones and husks of their prey remains in the trap.

In the case of flytraps and drosera, the trap opens back up and the insect husks are either washed away with rain, or microorganisms eat away at the husks until it dissipates. In pitcher plants, the enzymes and microorganisms may continue to break down the insect husks until it is either absorbed or washed out with an abundance of rainfall.

Do Carnivorous Plants Photosynthesize?

Yes, carnivorous plants do still photosynthesize. Plants that don’t photosynthesize becomes parasitic or symbiotic with another plant, rather than carnivorous. Plants evolved carnivorous behaviors because they adapted to live in soils that are nutritionally poor; that doesn’t meant they avoid those nutrients. See the linked article for more information on carnivorous plant photosynthesis!

Can Carnivorous Plants Eat Any Meat, or Just Insects?  

We’ve all been there as kids, having gotten this brand new venus flytrap knowing it eats meat, and deciding to feed it some ground beef from dinner. Except… That’s really bad for your carnivorous plant. (In fact, you shouldn’t even feed them raw meat. If you really want to give your carnivorous plant a treat, give them a cricket.)

The cooking oils and spices particularly aren’t great for the plant. While most carnivorous plants are actually insectivorous, meaning they consume insects alone, some larger plants have been known to digest reptiles and small mammals. It’s really a matter of what fits in the trap.

Conservation Threats to Carnivorous Plants

Carnivorous plants are a precious part of our world, and they’re under threat by habitat loss, pesticide pollution, poaching, and a changing climate:

Habitat loss caused by human development, whether for agricultural or urbanization purposes, can put a strain on carnivorous plant populations. Habitats around recent development can also change, which results in loss of suitable habitat for these plants as well.  

Pesticide pollution from agricultural farms and home maintenance practices wash into the water ways and into the bogs where many carnivorous plants flourish, killing the plants along with many of their pollinators and prey.

Poaching isn’t something that a lot of people think about when it comes to plants, but it is by far one of the most prevalent conservation threats of any endangered, rare, or even novelty plant. Orchids and carnivorous plants are among the most popular plants for poaching. Because carnivorous plants can be time consuming or difficult to grow in a nursery setting, they are often poached from the wild, which leads to a strong decline in their population overall.

Rapid changes in the weather pattern and temperature can be too much for plants’ natural adaptation. A volatile climate is disastrous not because plants cannot adapt to it, but because they don’t have the natural timeline to adapt to changes. Human-caused climate changes are happening at an exceedingly quickening rate that threaten both plant and animal species.