Nepenthes bicalcarata

Ever imagine what would happen if a vampire bit a Nepenthes? Really? Me too! Well, wonder no more. Nepenthes bicalcarata is our fanged tropical pitcher plant. Fortunately, N. bicalcarata doesn’t turn to ash in the sun but, as a lowland Nepenthes, it does prefer the shade of peat swamps. Another vampire-esque characteristic of N. bicalcarata is its uncanny robustness. The plant is one of the largest species of Nepenthes, towering 65 feet (20 m) into forest canopies with a supporting stem thickness of 1.4 inches (3.5 cm). N. bicalcarata has also symbiotically evolved alongside a unique species of carpenter ant, providing dwelling and food in exchange for protection and increased nitrogen. I’m not sure how that plays into the vampire comparison, but it’s super fascinating and we’ll dive into the details, below. First, let’s learn a bit more about the background of our fanged pitcher plant:

In 1873, Joseph Dalton Hooker (for whom Nepenthes x hookeriana, a natural hybrid between N. rafflesiana and N. ampullaria, was named) formally described N. bicalcarata from specimens collected by Odoardo Beccari and Hugh Low near Lawas River in Borneo. This type specimen, “Low s.n.” lived at the Royal Botanic Gardens, Kew, alongside another specimen collected by Johannes Elias Teijsmann that, in 1880, was described as unique species Nepenthes dyak. Today, we know N. dyak to by conspecific with N. bicalcarata (members of the same species).

British explorer Frederick William Burbidge (Nepenthes burbidgeae is name after him) collected N. bicalcarata for Veitch Nursery (for more information on Veitch Nursery, see our N. veitchii page) in 1879. Plants were cultivated for a few years and distributed to collectors in 1881, at the peak of collector interest in NepenthesThe Gardeners’ Chronicle of the time mentions N. bicalcarata:

Then there is N. bicalcarata, a most robust habited kind with sturdy foliage and bag-like pitchers provided with a vicious-looking rat-trap-like apparatus in its lid which renders it very distinct from its neighbours.

Our vampire Nepenthes remained a rarity for some time, costing a whopping £3.3s (about £370 or ~$480 adjusted for inflation) per plant as compared to the rare and exotic N. rajah and N. northiana at £2.2s (£245 or ~$318 in today’s money) per plant.

Unique biology of Nepenthes bicalcarata

Trap characteristics

Unfortunately, the fangs of Nepenthes bicalcarata are not used to suck blood. They are a bit of a conundrum, with multiple theories surrounding their evolutionary purpose. What we know for a fact: N. bicalcarata’s fangs are extensions of a pitcher’s peristome and contain some of the largest nectaries (nectar-secreting glands) of any plant. They hang above the open mouth of the pitcher and a buildup of nectar frequently forms venomous-looking droplets at their tips.

Frederick William Burbidge hypothesized that the sharp fangs deter animals that would otherwise reach inside pitchers to fish out and steal prey. I know that catching fangs in the back of the arm or head (don’t vampires bite necks?) would deter me. Of course, this hypothesis is partially defeated by Charles Clarke’s observation that tarsiers and monkeys simply rip the pitchers open below the peristome to eat their contents and avoid the fangs altogether. It seems to me that this would do the opposite of the hypothesized defensive purpose since the energy needed to replace a pitcher is certainly greater than that lost to some scavenging monkeys. It is important to note that the rate at which mammals mauled N. bicalcarata pitchers was lower than the attack rate of other Nepenthes species like N. rafflesiana.

Another alternate hypothesis from Clarke is that the fangs lure prey into a precarious position over the pitcher mouth. Drunk on nectar secreted from the fangs, prey loses footing and falls into the pitcher where it becomes lunch. N. lingulata uses a similar trapping mechanism, but with a single “fang” that emerges from the lid rather than peristome. 

N. bicalcarata peculiarities continue when we realize that the glandular region of the pitcher persists almost the entire way up to the peristome. Like N. ventricosa and N. ampullaria, this leaves no room for a slippery, waxy zone inside the pitcher. This may actually assist the symbiotic ants who need to retain footing as they venture inside the pitcher. Fun fact: In 2004, a study found that the peristome of N. bicalcarata is three times more effective at capturing prey when wet due to the large increase in slipperiness. Luckily, the plants grow in hot, humid conditions where peristomes can stay slick.

Other notable characteristics

In the wild, hollow tendrils of Nepenthes bicalcarata are home to a unique species of carpenter ant, Camponotus schmitzi. Frederick William Burbidge first noted the unique relationship in 1880. In 1904, Odoardo Beccari hypothesized that there was a give-and-take relationship with the ants with some feeding on prey caught by bicalcarata, and some falling prey to the plant. In 1990, E. O. Wilson and B. Hölldobler suggested that C. schmitzi and N. bicalcarata have a mutually beneficial, symbiotic relationship. Charles Clarke published research findings in 1992 and 1998 and Roger Kitching  published findings in 1993 and 1995 that all support the mutualism hypothesis. As it turns out, C. schmitzi is only found on N. bicalcarata, and is wholly dependent on it for food and shelter.

An important term to understand is myrmecotrophy, or the ability for plants to obtain nutrients from ants. The relationship is complex, and leverages multiple interactions to the benefit of both. Nepenthes bicalcarata uses ants like little minions to do its bidding, and in return, the ants receive food and shelter. N. bicalcarata obtains 42% to 76% of foliar nitrogen via Camponotus schmitzi excrement and ant remains. In addition to this, C. schmitzi increases nitrogen retention by themselves eating fly larva laid within pitchers that would otherwise consume prey nutrients, then leave the pitcher resulting in a net loss of nutrients. Ants pre-digest these fly larva and relinquish it to the plant via excrement. Yum! What’s more is that C. schmitzi has been observed mauling prey caught by N. bicalcarata, preventing its escape.

Think we’re done with the benefits? Well, the rabbit hole goes even deeper! Camponotus schmitzi will tune-up pitcher efficiency by cleaning the peristome of fungal hyphae and other contaminants. Dennis and Marlis Merbach demonstrated that C. schmitzi also protect N. bicalcarata from pitcher-destroying weevils.

When not cleaning the plant, removing pests, attacking prey, or predigesting food for Nepenthes bicalcarata, Camponotus schmitzi is chilling. And by chilling, I mean that they’re hiding away to avoid scaring off potential bicalcarata prey. What’s unique about this is that other myrmecophytic ants tend to be uber terrirorial, attacking other insects who invade their space.

Camponotus schmitzi also prevents putrefaction of pitcher fluid and subsequent death of the larva they feast upon by diving for 30 seconds at a time into the pitcher fluid and swimming to large prey. They cooperatively haul prey from a watery grave to the plant’s peristome. This maintains a healthy pitcher ecosystem and may even prevent the pitcher itself from rotting. To keep things copacetic and prevent the immediate digestion of it’s mutualistic buddies, N. bicalcarata maintains a less acidic pitcher fluid than other Nepenthes species. In fact, it lacks digestive enzymes. This does hinder the plant’s ability to digest true prey, and makes it more reliant on the ants.

Given all of these benefits, one might assume that Nepenthes bicalcarata is as dependent on Camponotus schmitzi as C. schmitzi is on it. However, this isn’t the case. N. bicalcarata will do A-OK without the ants in cultivation, reaching maturity and flowering without its mutualistic buddies. That said, there seem to be few plants in cultivation over 6.5 feet (2 m) in height, and this could be because the ants favor upper pitchers for their homes (lower pitchers get submerged during rains, drowning ants). Plants with ant amigos also tend to have more, larger petioles and larger pitchers from the increased available nitrogen. Without ants, N. bicalcarata is a good candidate for foliar fertilizing.

Other Nepenthes species & hybrids