HerbalEGram: Volume 14, Issue 5, May 2017

In his book Insectivorous Plants, which was first published in 1875, English naturalist and evolutionary biologist Charles Darwin wrote that the Venus flytrap (Dionaea muscipula, Droseraceae) “is one of the most wonderful [plants] in the world.”¹ Now, that “wonderful” plant is still being threatened in the wild by a combination of poaching (and overharvesting in general), habitat loss, fire suppression, wetland drainage, seed collection, and other factors.^2-4

Based on information from the North Carolina Natural Heritage Program’s database, it is estimated that approximately 73,000 to 158,000 individual plants remain in the wild. “This may sound like a lot, but these populations are very imperiled and the threats to these populations are high,” wrote Laura Robinson, a botanist with the Natural Heritage Program (email, April 4, 2017).

The Venus flytrap is native to a small area in southeastern North Carolina and northeastern South Carolina,⁵ but it has reportedly been naturalized in other states, including Florida and New Jersey.⁶ Specifically, it is found within an approximately 75-mile radius of the port city of Wilmington, North Carolina.² The colonial governor of North Carolina, Arthur Dobbs, who may have been the first to document the species, noted the plant’s limited geographical range in a 1759 letter to his friend, English botanist Peter Collinson: “We have a kind of Catch Fly Sensitive which closes upon anything that touches it. It grows in this latitude 34 but not in 35°.”⁷

According to the book Dionaea: Venus’s Flytrap (Redfern Natural History Productions, 2012), the Venus flytrap has been entirely eliminated from about 1.5 million acres of habitat across the northeastern part of its natural range, and has also been eliminated from south and central parts of its range. Although a few populations persist along the extreme western periphery of the plant’s range in the Sandhills region of North Carolina, these populations are separated by more than 50 miles from all other Venus flytrap sites. Furthermore, most of the limited remaining populations include less than 500 individual plants, and the authors consider it unlikely that these populations will be viable in the long term.⁴

In addition to capturing insects, arachnids, and, occasionally, even small frogs and snails,⁸ the Venus flytrap, like other carnivorous plants, has captured the imagination of many people for years. Exaggerated depictions of carnivorous plants, often oversized and man-eating, have been featured prominently in fictional works, such as Sir Arthur Conan Doyle’s 1880 short story The American’s Tale: An Arizona Tragedy, John Wyndham’s 1951 novel The Day of the Triffids, and the 1960 film and subsequent musical The Little Shop of Horrors⁹ (and the 1986 film adaptation of the musical). Fascination (propelled by Darwin’s 1875 book), and perhaps often obsession, with carnivorous plants in general and with the Venus flytrap in particular have led to extensive harvesting of the plant in the wild, and this is one of the main causes of its decline.

Current Outlook

Poaching

The Venus flytrap became officially protected by North Carolina legislation in 1956, but overharvesting has remained a problem for decades.² In 1981, it was estimated that between 1.4 million and 4.5 million plants were sold annually within the United States, the majority of which were thought to be of wild origin. In 1990, 1,077,227 plants (mostly bulbs, but also 200,000-300,000 whole plants) were exported from North Carolina , and none were exported from South Carolina.¹⁰

On December 1, 2014, it became a felony in North Carolina for any person to dig up, pull up, take, or aid in taking or carrying away a Venus flytrap plant, or the seed thereof, growing on the land of another person, or from the public domain, without a permit signed by the landowner. Previously, this was a misdemeanor, punishable by a maximum fine of $50, but offenders can now face up to two years or more in prison.^2,11

In South Carolina, it is a misdemeanor to “cut, collect, break or otherwise destroy” Venus flytrap plants on private or public property without the owner’s consent. If convicted, offenders “shall be fined not more than two hundred dollars or imprisoned not more than thirty days nor less than five days. Each violation shall constitute a separate offense.”¹² In the past, Venus flytrap poaching has apparently been “minimal” in South Carolina, where a small percentage of the plants occur.¹⁰

The Venus flytrap grows in boggy areas with moist, acidic soil that is usually poor in nutrients.⁶ “People find them in their backyards occasionally,” wrote Debbie Crane, director of communications for the North Carolina chapter of The Nature Conservancy (TNC), a nonprofit conservation organization that works around the world to protect ecologically important lands and waters for nature and people (email, March 28, 2017). “And we know of a couple of spots where they are likely, but the property is in private hands. It is fair to say that most of the flytraps are on property owned by TNC, other land trusts, the government [state and federal], and the US Department of Defense.”

In January 2015, four men were arrested for poaching Venus flytraps on the Holly Shelter Game Land preserve. Although TNC originally protected much of what now makes up this 63,494-acre preserve, it is now owned by the North Carolina Wildlife Resources Commission, a state government agency created to conserve and sustain the state’s fish and wildlife resources. The men had 970 plants in their possession and became the first people charged with a felony for poaching the Venus flytrap. Two of the men were sentenced to 24 months of supervised probation, one was sentenced to 12 months of supervised probation, and the other, who was the only one to not plead guilty, was sentenced to six to 17 months in prison.^2,3

The Venus flytrap, which can be smaller than a US dime, can be found in Croatan National Forest, on land owned by the North Carolina Division of Parks and Recreation, and on Wildlife Resources Commission game lands in Pender, Brunswick, Onslow, and New Hanover counties.¹³ The plant also occurs on several preserves owned by TNC, but the only one of these that is open to the public is the Green Swamp in Brunswick County, according to Crane.

“We’ve had flytraps poached on our land,” Crane told Scientific American, adding that thefts of a thousand plants at a time were all too common.³ “What makes poaching so sad and stupid is that the people who are doing it are local folks,” she continued. “They’re not making much money off of it. They’re selling the bulbs for maybe 25 cents.”

Other sources, however, indicate that the poaching can be lucrative.^10,13 Poachers reportedly often sell to out-of-state distributors, and a single plant typically fetches between $7 and $10 at a store.¹³

In the past, the Wildlife Resources Commission made about 10 to 20 arrests per year for poaching on land it controls, but the arrests usually amounted to nothing more than a slap on the wrist before poaching became a felony.¹³ “A lot of guys we catch—it’s sad to say—it’s a family tradition,” Sergeant Brandon Dean, of the law enforcement division of the Wildlife Resources Commission, was quoted as saying. “We caught their dad and their dad’s dad.” Dean also reportedly estimated that one person might be caught for every 200 instances of poaching.²

Previously, some offenders continued to poach Venus flytraps even after as many as 20 encounters with law enforcement. The results of poaching could also be seen at depleted and extirpated sites.¹⁰

According to Dean, when poachers are caught it is often because authorities have been tipped off by other poachers who are protecting “their turf,” or by others, such as bird watchers or hikers.²

It is too soon to determine whether the stiffer penalties for poaching have helped mitigate the situation. “But [they] certainly [haven’t] done any harm,” Crane wrote. “The first arrests got lots of attention, which is a good thing.”

In The New York Times, Dean was quoted as saying, “I would like to think with it being a felony, it put a damper on it. The teeth have definitely been sharpened.” He is, however, reportedly doubtful that the poaching will stop completely. He noted that the burden is on enforcers to prove that plants were poached, which is difficult because, according to him, there is no way to distinguish between a plant that was poached from the wild and one that was legally raised in a greenhouse.²

However, according to a 2010 National Geographic article, the North Carolina Department of Agriculture, at the time, had been dabbing Venus flytraps in the wild with a harmless, invisible dye that glows in ultraviolet light to allow authorities to determine whether flytraps being sold were poached.¹⁴

Interestingly, in 2013, Kurup et al. discovered that in the presence of ultraviolet radiation the Venus flytrap (specifically the inside portion of the lobes of the traps) and some other carnivorous species (e.g., pitcher plants in the genus Nepenthes [Nepenthiaceae]) can attract prey by naturally emitting fluorescent blue light that is clearly visible to insects and other arthropods.¹⁵ According to Baby Sabulal, PhD, principal scientist at the Jawaharlal Nehru Tropical Botanic Garden and Research Institute in Kerala, India, and co-author of the study, the Venus flytrap that was analyzed was collected from their garden collection and had not been treated with any dye (email, March 31, 2017). Furthermore, the team consistently found even stronger fluorescent emissions in the Nepenthes species that were analyzed, he wrote.

Conserving the Venus flytrap may also have implications for tourism and, consequently, the economy in North Carolina. “We’ve had people from all over the world come here to see flytraps,” Crane was quoted as saying. “If the plants are gone, [some] tourists are not going to visit.”³

Also according to Crane, poaching isn’t necessary because the plants can easily be cloned (e.g., by cutting). “Flytraps love cloning,” Crane was quoted as saying. “You can create them in a greenhouse very easily, and it’s being done all over the world. They are being sold legally in a lot of places because they are cloned.”³ The Venus flytrap can also be grown from seed, but it usually takes several years.¹⁶

According to TNC, there is a good chance that plants sold at a flea market, on the roadside, or online were poached. To help protect Venus flytraps, TNC recommends buying from reputable dealers that do not sell poached stock.⁵

Development and Other Threats

“Poaching is a big problem, but so is development,” Crane wrote. Many Venus flytrap habitats have been lost over the last century to development.³ According to Dionaea: Venus’s Flytrap, a 2005 follow-up survey of South Carolina Venus flytrap sites found that 70% of the recorded sites had been replaced with golf courses and parking lots.⁴

Protecting flytrap habitats from development and other threats may also have implications for other rare species. One Venus flytrap site was found to support as many as 42 other rare plant species within 25 square meters.⁴

“TNC and the North Carolina Coastal Land Trust have done a lot of work to protect flytrap territory,” Crane wrote. “Protecting and restoring habitat is probably more important than efforts focused on poaching.” (One expert peer reviewer of this article noted that poached habitat can still feasibly regrow flytraps while paved habitat obviously cannot.)

The mission of the North Carolina Coastal Land Trust is “to enrich the coastal communities of North Carolina through conservation of natural areas and working landscapes, education, and the promotion of good land stewardship,” according to its website.¹⁷ It has become the largest land trust, geographically, in the state, and it is qualified to accept and hold conservation agreements. Landowners who are interested in protecting their land from development may choose to enter into a conservation agreement with a qualified conservation organization or government body. This legally binding agreement permanently limits the uses of all or part of a property in exchange for tax savings, charitable contributions deductions, income tax credits, and lower property taxes for the landowner.¹⁸

The Coastal Land Trust holds conservation agreements on two properties with flytraps. In addition, it has purchased in fee title three properties with flytraps; it owns and manages two of these as nature preserves, and it transferred the other (which abuts part of the Croatan National Forest) to the Wildlife Resources Commission to be managed as game land (email from Janice Allen, deputy director of the Coastal Land Trust, April 3, 2017).

Although many of the remaining known Venus flytraps occur on protected lands, development is still a significant concern for at least two reasons, according to Crane. First, TNC, which manages preserves in all 50 US states and has protected more than 700,000 acres in North Carolina alone (from the Outer Banks to the Southern Blue Ridge Mountains),¹⁹ suspects the plants also occur on some unprotected private lands because those lands are similar to the public lands where the plants are known to occur. “If those lands are developed, then the plants [that TNC suspects grow there] will be lost as well,” she wrote. Second, “development can have a negative effect on nearby lands that may already be protected by draining them, causing runoff, or preventing the use of fire to restore land. When you have neighborhoods close by, it is really hard to put controlled burns on the ground.”

Fire is particularly important for the Venus flytrap. Without it, shrubs take over and shade out the sun-loving plants, which need an open understory (the layer of vegetation, especially the trees and shrubs, between the canopy and the ground cover) to survive. Fire suppression may help protect human developments, but it has affected large swathes of land that Venus flytraps inhabit, including the Green Swamp. TNC is working to restore these habitats through controlled, or prescribed, burns that mimic natural fires.^5,6

“We do use controlled burning to manage habitat for flytraps and other plants,” Crane wrote. “Ideally, the fires should be put on the land in a regular interval.”

There is evidence that with a fire return interval (i.e., the time between fires in a specified area) of more than five years, Venus flytrap populations decline precipitously. In addition, some data show that the largest and densest remaining flytrap populations occur in places with the longest and most regular history of burning.⁴*

In the future, rising sea levels may also pose a concern. “[Venus flytraps] only occur in low-lying areas near the coast, so, yes, over time, sea level rise will likely affect them,” Crane wrote.^†

Changing soil fertility may also affect the Venus flytrap. The soil of bogs typically contains little nitrogen and phosphorus. So, the Venus flytrap, like other carnivorous plants, has adapted to obtain these nutrients in other ways, thereby compensating for the deficiencies of the soil. However, pollution from power plants and agricultural runoff has added extra nitrogen to many bogs in North America, and this can prove fatal to carnivorous plants, presumably including the Venus flytrap, which are so attuned to low levels of nitrogen.¹⁴

Conservation Status and Regulations

The Venus flytrap is considered vulnerable^‡ according to the Red List criteria of the International Union for Conservation of Nature (IUCN).²⁰ Version 3.1 of the Red List Categories and Criteria states that a taxon is vulnerable “when the best available evidence indicates that it meets” at least one of the listed criteria, “and it is therefore considered to be facing a high risk of extinction in the wild.”²¹ The Venus flytrap was among 250 rare and threatened species included in the first IUCN Plant Red Data Book, published in 1978. The publication arose from pioneering work by botanists at the Herbarium at the Royal Botanic Gardens, Kew in England, who recognized that the plights of many plant species in danger of extinction were less publicized than the plights of some rare and charismatic animals.⁸

The IUCN’s Red List of Threatened Species is the world’s most comprehensive information source on the conservation status of plant, animal, and fungal species. The Red List Categories and Criteria provides an explicit, objective framework for classifying species at high risk of global extinction, based on parameters such as population reduction and restricted geographic range.²²

The Venus flytrap is also currently listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).²³ CITES, which came into effect in 1975, is an international agreement intended to ensure that international trade of certain animal and plant species does not threaten the survival of those species. Currently, 183 countries, or Parties, including the United States, have voluntarily agreed to adhere to the Convention. CITES is legally binding for the Parties, but it does not take the place of national laws. Instead, each Party must adopt domestic legislation to ensure that CITES is implemented at the national level.²⁴ Currently, more than 35,000 species of animals and plants, including the Venus flytrap, are listed among the three CITES appendices, which afford varying degrees of protection.^24-25 

Appendix II includes species that are not necessarily threatened with extinction but for which trade must be controlled to avoid overexploitation. For these species, including the Venus flytrap, “an export permit or re-export certificate issued by the Management Authority of the State of export or re-export is required. An export permit may be issued only if the specimen was legally obtained and if the export will not be detrimental to the survival of the species. A re-export certificate may be issued only if the specimen was imported in accordance with the Convention.”  However, import permits are not needed for species listed in Appendix II “unless required by national law.”²⁵

In October 2016, a petition filed with the Secretary of the Interior requested the United States Fish and Wildlife Service (USFWS) to immediately protect the Venus flytrap as a recognized endangered species under the Endangered Species Act (ESA) of 1973.** The ESA states that a species shall be determined to be endangered or threatened based on any of five factors, and the petitioners wrote that the Venus flytrap is threatened by at least four of those factors (i.e., curtailment of habitat, overutilization, inadequacy of existing regulatory mechanisms, and other natural or manmade factors). “The decision by the [USFWS] not to list the Venus Flytrap as Threatened or Endangered in 1993 has led to continuing declines in its range and abundance since then,” the petitioners wrote.²⁷

Benefits for plants and animals that are listed as endangered or threatened under the ESA include the following: protection from being jeopardized by federal activities, protection from having critical habitat destroyed or adversely modified, restrictions on take and trade, a requirement that the USFWS develop and implement recovery plans for listed species under US jurisdiction, authorization to seek land purchases or exchanges for important habitat, and federal aid to state and commonwealth conservation departments with cooperative endangered species agreements. Listing can also encourage conservation efforts by other agencies, independent organizations, and individuals.²⁸

“We have reached a situation in which there are more flytraps in captivity than in the wild,” Donald Waller, PhD, a professor of botany at the University of Wisconsin-Madison who co-authored and signed the petition, was quoted as saying. “That might be construed as good news, if it assures they will survive in captivity, but it's distressing for ecologists and conservation biologists. A population can only persist and evolve in its native habitat, and we've already seen the disappearance of 90 percent of wild plants. We have lost whole bogs, populations and individuals.”²⁹

Medicinal Properties of the Venus Flytrap

The Venus flytrap contains compounds that can benefit human health, including naphthoquinones, phenolic acids, and flavonoids.³⁰ 

According to a 2013 review by Gaascht et al., more than 15 compounds have been isolated from the Venus flytrap, although most of these are also found in other plants. At the time of the review, only one compound thought to be unique to the Venus flytrap with medicinal potential had been isolated: diomuscipulone. This naphthoquinone, however, has apparently not been tested for its biological activity.³⁰

Many of the compounds found in the Venus flytrap, including the naphthoquinone plumbagin (also present in Plumbago zeylanica [Plumbaginaceae] and other plants) and the phenolic acids ellagic acid (also present in pomegranate [Punica granatum, Lythraceae] and many other plants) and salicylic acid (also present in Salix spp. [Salicaceae]), have been shown to modulate the NF-ĸB cell-signaling pathway. This may be significant because this pathway is involved in the development and progression of many types of cancers.³⁰

Several of the compounds found in the Venus flytrap, including salicylic acid and the flavonoids quercetin and kaempferol (which are both present in Ginkgo biloba [Ginkgoaceae] and many other plants), have been the subjects of pharmacokinetic studies and clinical trials. Though most studies show that these compounds have poor bioavailability, it has been shown that co-treatment with a natural compound like quercetin or kaempferol and a chemotherapeutic drug like cisplatin or etoposide is more efficient than a single treatment, probably because of the ability of the natural compounds to block a specific drug resistance mechanism used by cancer cells.³⁰

Plumbagin may be one of the most promising anticancer compounds present in the Venus flytrap.³⁰ It has demonstrated anticancer and antiproliferative activities in animal models and cell cultures and has been shown to target a wide range of cancer types, including breast cancer, lung cancer, ovarian cancer, acute promyelocytic leukemia, and prostate cancer.³¹

In addition, plumbagin and its derivatives appear to have antibacterial properties. A 2013 in vitro study showed that the plumbagin derivatives maritinone and 3,3’-biplumbagin (isolated from a plant other than the Venus flytrap) were 32 times more potent than the antimycobacterial drug rifampicin against a strain of Mycobacterium tuberculosis that was pan-resistant (i.e., resistant to all five first-line anti-tuberculosis drugs). The authors concluded that these two derivatives have the potential for development as new anti-tuberculosis drugs, especially against resistant strains.³²

In the 1970s, the German physician Helmut Keller, MD, observed a Venus flytrap while in a flower shop in Maine and wondered if the plant contained substances that could be used selectively against tumor cells. He eventually developed a patented extract of the Venus flytrap called Carnivora.³³ Although some anecdotal evidence suggests that Carnivora may be an effective cancer therapy,³⁴ it does not appear to have been the subject of any human clinical trials. According to the Carnivora website, its manufacturing process does not use any Venus flytraps from wild habitats.³⁵

Daniel Moerman’s Native American Ethnobotany, a highly respected compilation of the ethnobotanical uses of North American plants by Native American peoples, does not indicate that the Venus flytrap was used medicinally by Native Americans, but it does state that the Cherokee used a “small piece of plant chewed and spat on bait for fishing.”³⁶

Although the Venus flytrap does not seem to be a major part of the commercial herb trade, the plant does contain compounds with demonstrated anticancer effects and other potentially beneficial biological activities.

Botany and History of the Venus Flytrap

The Venus flytrap is an herbaceous perennial that, from a rhizome, produces a low-growing rosette (which can be five inches tall and eight inches wide) of up to eight or more bristly, spreading, basal leaves (traps) that can each be five inches long. White flowers bloom in spring, from about May to June, on leafless stems that rise above the foliage up to about one foot tall.¹⁶

The plant belongs to a monotypic genus (i.e., it is the only species in the genus Dionaea). It is closely related to the waterwheel plant (Aldrovanda vesiculosa), which also belongs to a monotypic genus in the Droseraceae family (though there are extinct Aldrovanda species).⁸ The waterwheel plant is a rootless, free-floating, freshwater carnivorous plant that consumes aquatic invertebrates and has been called the “aquatic sister” of the Venus flytrap. Unlike the Venus flytrap, the waterwheel plant is considered endangered according to IUCN Red List criteria because, even though it is widely distributed geographically, it has declined over the last century to only 50 confirmed extant locations.³⁷

Phylogenetic analysis based on DNA sequence data has shown that the Venus flytrap and the waterwheel plant, which are the only known snap traps (a kind of active trap), are descended from a common sticky “flypaper” trap ancestor (i.e., one that captures prey using a sticky mucilage). This ancestor would have been in the Droseraceae family and would have been similar to sundew (Drosera) species, but it is presumed extinct. According to Gibson et al., the snap traps adapted to catch and retain larger prey, resulting in disproportionate rewards, compared to the sticky traps, which allow larger prey to escape. It has also been shown that the king sundew (Drosera regia, Droseraceae), a flypaper trap, is the closest known living relative of the two snap traps.³⁸ 

Because there is some disagreement in the scientific community about what exactly constitutes carnivory in plants, there is also disagreement about how many carnivorous plant species there are. For example, in 2009, Chase et al. proposed that some species not widely considered to be carnivores, such as species in the genus Stylidium (Stylidiaceae), and some species in the genera Potentilla (Rosaceae), Proboscidea (Martyniaceae), and Geranium (Geraniaceae), are just as carnivorous as other carnivorous species.³⁹

Regardless how many carnivorous plant species there are, and most sources indicate there are more than 600, the Venus flytrap may be the most famous of them all, probably largely because of its ability to snap shut so quickly.⁴⁰ Other active traps use mechanisms that are different from the two snap traps to capture prey. For example, aquatic bladderwort species (i.e., aquatic species in the genus Utricularia [Lentibulariaceae]) pump water out of the bladder of the plant, which decreases pressure inside the bladder and creates a vacuum that rapidly sucks prey in to be digested when the trapdoor is triggered to open even slightly.^38,41 By even greater contrast to the snap traps, pitcher plants (species in the genera Sarracenia [Sarraceniaceae], Nepenthes, and others), for example, are passive traps (specifically pitfall traps) that use nectar to lure prey to slip into the trap.⁴¹ Thus, the snap traps are unique, and this uniqueness is likely contributes to the Venus flytrap’s popularity. 

The Venus flytrap’s Latin binomial Dionaea muscipula originated from a published letter, dated September 1, 1768, by English naturalist John Ellis, who credited the genus name to Swedish naturalist Daniel Solander. Ellis wrote: “At the request of Mr. Collinson, the ingenious Dr. Solander … dissected this plant before some of his friends; and from the beautiful appearance of its milk-white flowers, and the elegance of its leaves, thought it well deserved one of the names of the goddess of Beauty, and therefore called it Dionaea…. I shall only add a specific name to distinguish it from others of this genus, that may possibly be discovered hereafter. From the structure then and particular moving quality of its leaves when irritated, I shall call it Dionaea Muscipula, which may be construed into English … either Venus’s Flytrap or Venus’s Mousetrap.”⁴² In Greek Mythology, Dione is the mother of Aphrodite, the goddess of love and beauty, whose Roman counterpart is Venus. In Latin, “muscipula” means mousetrap.

Ellis later sent a letter, dated September 23, 1769, to Swedish botanist and “Father of Modern Taxonomy” Carl Linnaeus, in which he described the Venus flytrap. Ellis also enclosed a picture of the plant with his letter.⁴³ Linnaeus described the plant as a “miraculum naturae,”³⁹ but apparently rejected the idea that a plant could consume an animal, saying that would go “against the order of nature as willed by God.” He reasoned that the sensitive plants capture animals only by accident, and that once a captured animal stopped struggling, it would be released.¹⁴

In his book Travels, published in 1791, American naturalist William Bartram, the son of botanist John Bartram, wrote the following of the Venus flytrap: “Astonishing production! See the incarnate lobes expanding, how gay and ludicrous they appear! Ready on the spring to intrap incautious deluded insects, what artifice! There behold one of the leaves just closed upon a struggling fly, another has got a worm, its hold is sure, its prey can never escape—carnivorous vegetable! Can we after viewing this object, hesitate a moment to confess, that vegetable beings are imbued with some sensible faculties or attributes, similar to those that dignify animal nature; they are organical, living, and self-moving bodies, for we see here, in this plant, motion and volition.”^7,44

Years later, Darwin also knew better than Linnaeus, but even he could not imagine some of the plant’s abilities before observing a specimen for himself. In a letter to English botanist Daniel Oliver, dated September 11, 1860, Darwin wrote: “Lastly would you look at the Dionaea (if you have living specimen) and observe whether the hairs are viscid, for it almost passes my belief that the leaf can snap so quick as to catch a fly, unless it be in some degree entangled….”⁴⁵

Darwin later learned differently, and, in Insectivorous Plants, wrote: “the sensitive filaments of Dionaea are not viscid, and the capture of insects can be assured only by their sensitiveness to a momentary touch, followed by the rapid closure of the lobes.”¹

The No-Fly Zone: How the Venus Flytrap Catches and Digests Prey

The Venus flytrap uses sweet-smelling nectar to lure prey into the traps.16 There are between three and six trigger hairs (trichomes) on the inside surface of each lobe of each trap.46 Presumably to prevent the plant from wasting energy by responding to non-prey stimuli, such as raindrops and dust, the trap will close only when one hair is touched twice or two hairs are touched within about 20 seconds, which indicates the plant can remember the first electrical signal for a short time.47 If a second signal is not received within about 20 seconds, the process resets, but if it is, the cells on the outer surface of the leaf expand rapidly and the trap shuts almost instantly (in about a tenth of a second; compared to the waterwheel plant, which can shut in about 10 milliseconds), and snaps from convex to concave.46,47 This type of movement is called thigmonasty (a non-directional response to being touched).6 More than three flicks of a trigger hair are necessary for the plant to begin to secrete the digestive enzymes that dissolve its prey. When the trapped prey struggles, it trips the trigger hairs repeatedly, and this struggle gives the plant a way to judge the amount of digestive enzymes needed, and thereby save energy. More electrical signals from the trigger hairs being tripped seems to correlate proportionally with more digestive enzymes being secreted.47 The nutrients from the prey are absorbed and, after five to 12 days, the trap reopens to release the leftover exoskeleton.46 While larger Venus flytrap plants produce larger traps, it has been shown that the number of traps per plant actually remains steady or even decreases as the plants grow larger. Smaller traps on smaller plants seem specialized for catching smaller prey, especially ants, and larger traps often catch spiders and beetles.38 After three to five meals, a leaf will no longer capture prey but will exclusively photosynthesize for about two to three months before it falls off the plant. After about 10 unsuccessful closures, a trap will no longer respond to touch and will only photosynthesize.46 It has been estimated that a Venus flytrap can live up to 20 years, or possibly longer.6

Conclusion

The Venus flytrap is a sophisticated, one-of-a-kind plant, but, ironically, it is the sophisticated adaptations that this plant has developed to survive and thrive that have led to the poaching that is now one of the main threats to the plant’s survival in the wild.

According to Professor Waller, who co-authored the petition to give the flytrap protection under the ESA, wild populations can be protected without reducing demand for the plant. “Let’s encourage [demand],” he wrote (email, March 30, 2017). “Flytraps can be easily propagated. But we do need to shut down poaching of plants from the few remaining wild populations. So why not give consumers a way to satisfy their demand for this plant by buying certified propagated plants? While we are at this, let’s ask for 50 cents or $1 per plant to protect and maintain wild habitats. Most of us would appreciate the chance to protect wild populations while indulging our passion for this plant.”

Waller also thinks that potential habitats for this species need protection from development and other threats. “Especially the larger blocks of habitat that work effectively to sustain regular new colonizations,” he wrote. “Second, these areas need active management if they are to function as habitat for the flytrap. In particular, we must sustain their hydrologic and fire regimes. In other words, we need to make sure they stay wet and burn regularly. Flytraps need sun and water, but they lose these when shrubs overgrow their habitats or people drain swamps and savannas.”

Flytrap habitats, however, cannot be burned every year or all at the same time, according to Waller. “Burning various patches of habitat in alternation with each other allows a steady stream of new favorable patches to colonize,” he wrote.

“This plant charms us all,” Waller wrote. “Carnivorous plants are all fascinating, but this plant is the most fascinating of all. It is also the sole terrestrial representative of a remarkable evolutionary event — the evolution of a rapidly closing snap trap.”

* One expert peer reviewer of this article wrote, “the best wild populations from my experience occurred on military lands that burned from regularly exploding ordinance.”

† According to an expert peer reviewer of this article, sea level rise is not an immediate threat to the Venus flytrap. The reviewer did a GIS model last year and found that the lowest elevation sites with Venus flytraps were 26 feet above sea level.

‡ According to an expert peer reviewer of this article, the current conservation assessment for the Venus flytrap found on the IUCN Red List website is out of date, both because it is 10 years old and, more importantly, because it used the previous version (Version 2.3) of the IUCN Red List Categories and Criteria. According to the reviewer, a reassessment is needed. “This is not to predict that the category assigned (vulnerable) will be different, but the criteria used will be more relevant to the data available,” the reviewer wrote.

** Though the law establishes a two-year timeline for species to be listed under the ESA, a fairly recent study found that it takes, on average, 12.1 years for a species to be listed. Some species went through the process in six months, but some species, including many flowering plants, took 38 years to be listed (most of the history of the ESA).²⁶

—Connor Yearsley

References

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