Daily Archives: October 20, 2011

Thursday is Resource Day

Lots of interesting stuff in the mailbox this week, and all I have time for is to note that the new issue of Reptiles magazine just arrived. I’m very serious about getting serious vivarium people, serious miniature garden people, and serious plastic casting people together for a bit of a discussion. Among other things, we could all have a LOT of fun.


Absolute Surefire Steps to Kill Your Venus Flytrap: Step 6

Curious about the context? Check out the introduction.

Some of the content in this series appeared, in much shorter form, in Gothic Beauty magazine.

Step 6: Feed it hamburger.

Were I to assume that the publishing business will be in anything approximating a decent shape in five years, I’d put together a little book full of stupid memes, tropes, and general comments that have no attribution whatsoever. I’ve already got a great list of them: “Put butter on a burn.” “Poke yourself with a pencil lead, and you’ll get lead poisoning.” “Put boiling water in your ice cube trays, and the water will freeze faster.” “Mosquitoes die as soon as they bite you.” “You’ll make more money if you give away all your goods, services, or content for free.” “George Lucas is a cinematic genius.” Hell, I could do the book just on the idiotic advice wannabe writers give each other, such as “Writers make an average of $37.50 an hour” or “If you’re afraid that someone’s going to steal your idea, write it up and mail it to yourself so you’ll have proof.” (This last one always comes from individuals who think that writing Absolutely Fabulous/Farscape slashfic is a great idea, and would do so if they had the time.)

One of the biggest ones on that hypothetical list, though, directly involves carnivorous plants. I don’t know who started the meme “Even eats hamburger!” involving Venus flytraps, but it’s everywhere. If it isn’t plastered on flytrap containers in grocery stores and home improvement centers, it’s repeated over and over in any number of poorly researched articles and children’s books. The cliche of Venus flytraps eating hamburger is as established as the comparison between the early “proto-horse” Hyracotherium and the fox terrier, and I have it spouted back at me over and over. The difference between flytrap/hamburger and Hyracotherium/fox terrier is that fox terriers don’t die because of that cliche perpetuation.

To take on this misperception and send it back to Hell, we’ll need to look at three separate considerations. Before I go there, I won’t deny that it’s possible to feed carnivorous plants by hand. Based on recommendations from Peter D’Amato, I’ve fed tiny slivers of chocolate to Cape sundews, solely to watch the response. (It’s remarkably like a human’s, where the leaf wraps around the chocolate and drools on it.) But hamburger? Get a bag of assorted nuts and bolts and feed them one at a time to your flytrap, because it’ll cause less damage.

The first thing to consider is that flytraps get their common name for a reason. Readers of a certain age may remember a series of Life magazine encyclopedias on the sciences, profusely illustrated with black-and-white and color photos from the magazine. In the volume The Plants, carnivores received two pages, with one being dedicated to a large photo of a grasshopper with its head caught in a Dionea trap. Yes, that one was staged (among other things, a grasshopper with its head caught in a flytrap wouldn’t suffocate, as grasshoppers and other insects breathe through their abdomens), but that led lots of first-time flytrap owners to assume that their new plants could handle prey of any size. Trying this, though, usually meant that the prey rotted, the trap turned black and slimy, and ultimately the whole leaf fell off.

The reason for this has everything to do with the square-cube law: square the size of an object, and you cube its volume. A flytrap’s typical prey in the wild ranges from flies to small spiders to large ants because they’re large enough to offer a sufficient return. Flytraps and other carnivorous plants don’t capture and digest insects for energy the way animals do. They’re already getting plenty of energy from standard photosynthesis, and they’re eating insects for the additional nitrogen and phosphorus necessary for growth that they can’t get from the local soil. Any carnivore that produces its own digestive enzymes (and some don’t) has to take energy from maintenance, growth, and reproduction to secrete those enzymes, and they’re very energy-intensive. Hence, if the prey is too big for the plant to digest fully, it rots.

The second consideration? Flytraps can’t chew. For the last 600 million years or so of multicellular life on Earth, animals have some way to shred, crush, liquefy, or dismember food items, so those items get improved exposure to digestive juices. Spiders inject venom that liquefies prey from the inside, and scorpions both inject venom and use their claws to pulverize their prey. Millipedes and grasshoppers have shredding and pulping mouthparts. Mosquitoes, lampreys, and vampire bats all have specialized structures to draw up liquids from their food items. Birds carry gizzard stones that mash food before it’s passed to the intestines. Many carnivores, including Komodo dragons, pull their prey apart before swallowing the chunks. Even animals that swallow their prey whole, like pythons, have strong gastrointestinal muscles that crunch up and squeeze their food so the surface area exposed is increased. If you want a direct example, put your finger on your jaw joint and move your jaw from side to side. This motion allows your teeth to move laterally as well as vertically, thereby shearing and crushing food too bulky for simple up-and-down mastication to work. That side-to-side motion, along with the enzymes in your saliva, allow that lump of food, known as a bolus, to be digested that much faster than if you’d simply swallowed everything whole.

This, right here, is why we don’t have man-eating plants, as much as people nag and nuhdz me about growing them. It also explains why reported incidents of vertebrates being caught in carnivorous plants are so rare, and not just because insects and other arthropods outnumber us vertebrates by 9:1. Not a single carnivorous plant on the planet can chew, mash, chomp, or otherwise masticate its food. That’s not to say that they can’t do so with help: many animals, from spiders to crabs to frogs and geckos, live among carnivores and help themselves to excess prey. Green tree frogs live within Sarracenia pitcher plants and snag prey before it ever gets into the pitcher. Similar frogs are well-documented among the Heliamphora pitchers of South America, and some species of Heliamphora even have a slick spot within the pitcher that’s perfectly suited for a frog to camp for the day. The Borneo pitcher plant Nepenthes bicalcarata even encourages ants to nest within special chambers within its leaves, and the ants rapidly daisy-chain down into the pitchers and tear apart prey. Best of all, the South African Roridula can’t digest prey on its own at all, and depends upon a symbiotic species of ambush bug to feed upon prey animals caught on its leaves.

All of this sounds unfair to the plant, but it’s not. With N. bicalcarata, the ants live in a commensual relationship with the plant: the plant offers a living space and nectar for additional food, and the ants clean up large prey and attack anything dumb enough to molest the plant. With the tree frogs in Sarracenia and Heliamphora, they defecate into the traps while hanging out, thereby predigesting prey into a more easily accessible form of nitrogen. Some Nepenthes not only encourage this behavior with frogs, but with tree shrews and bats. And then you have the other commensual animals that live inside of traps, such as midge larvae and the like…

The poor Venus flytrap, though, has no such option. Once it ascertains that the item within its trap is potential food, it closes all the way, and seals the edges of the trap like a purse to retain digestive fluid. Nothing gets out, but nothing gets in, either, to help it. Even with sufficiently-sized prey, a couple of days of particularly cloudy weather, or some obstacle that prevents it from getting full sun, and the trap goes black and slimy. However, the odds of successful digestion are much better at that point than with something, say, the size of your thumb.

And the third consideration has everything to do with fat. As a general rule, as a food source, most insects are incredibly lean compared to most commercially raised and harvested livestock, and some individuals advocate following the lead of much of the world in more commercial farming of insects as food because of this. Really lean meat, such as scraped beef heart, is as fat-scarce as most of the insects consumed by Venus flytraps; again, the flytraps aren’t eating for energy, so they don’t have the need for large amounts of fat nor the enzymes necessary to digest it.

And hamburger? Oh, big cheeseburgers get called “cardiac arrest in a bun” for a reason. Really lean hamburger can run as low as seven percent fat, but most of the good stuff runs anywhere between 15 and 20 percent. Several local grocery stores sell big five-pound bullets of “fine ground beef,” and the fat content? At least 30 percent. We can bypass this a bit by grilling our burgers so the fat melts and runs off, but you’re still looking at a rather high percentage of fat in the final burger. The moment you see a flytrap grilling its food before it digests it, get a picture FAST.

Okay, so let’s recap. Very theoretically, you could feed your flytrap hamburger. It would have to be large enough to be worth the plant’s time and small enough to be digested without issue, and it would need to be extremly fat-free. If you think you can get just the right size, every single time, and make sure it was fat-free, go for it. Letting the plant catch its own insects, though, might be a much easier and saner option. Just saying.

Next: Step 7 – Keep it with other carnivores.