Could a human swing through the jungle on vines?
One of the most familiar scenes in the Tarzan movies is Tarzan swinging through the jungle on vines. My friends and I were discussing this and came to the conclusion that there aren't any vines in America strong enough to swing on, but maybe there are in Africa. Are any vines growing in trees strong enough to swing on?
Oh, sure. We're talking here about lianas, a generic term for the high-climbing woody vines found in the tropics. One of the biggest lianas, Entada gigas, turns up in both the Americas and Africa. It can reach well over a foot in diameter, more than sturdy enough to swing on. However, you can see where other problems might intrude--e.g., how you'd get a grip. The more you investigate, in fact, the more you realize vines wouldn't make for a practical system of locomotion. Investigate further still and you come to an additional conclusion: Tarzan creator Edgar Rice Burroughs didn't think they would either.
Vines first. Having consulted with George Angehr, who serves as tropical forest expert for the Straight Dope Science Advisory Board and moonlights as an ornithologist for the Smithsonian Institution in Panama, we can state the drawbacks of vines-as-jungle-bicycle as follows:
(1) As depicted in the Tarzan movies, the vines are attached at the top, free-swinging at the bottom. In reality, lianas are attached at the bottom (they're plants, with roots in the ground) and . . . well, maybe not free-swinging, but not reliably anchored at the top. Yank on a liana and one of two things is going to happen: nothing, because the top is entwined in the tree canopy, in which case, being secured at both ends, the thing won't let you do much swinging--at best you'll be able to sway back and forth; or it falls on top of you in a heap.
(2) Actually, a third thing might happen if you yank on a liana. As reported online and confirmed by Angehr, God's own collection of bugs and other little uglies may rain down on you. On the plus side, bisect a liana with a machete and you may find it contains drinkable water.
(3) Jungle vegetation is so densely matted, among other things by lianas, that even if suitable vines were available, attempting to swing on one would produce results less in keeping with Tarzan of the Apes than George of the Jungle.
Don't blame Edgar Rice Burroughs for steering the public wrong, though. Here's his description of how a young Tarzan gets around from the first book, Tarzan of the Apes (1914): "He could spring twenty feet across space at the dizzy heights of the forest top, and grasp with unerring precision, and without apparent jar, a limb waving wildly in the path of an approaching tornado. He could drop twenty feet at a stretch from limb to limb in rapid descent to the ground, or he could gain the utmost pinnacle of the loftiest tropical giant with the ease and swiftness of a squirrel. Though but ten years old, he was fully as strong as the average man of thirty. . . . And day by day his strength was increasing."
In short, Tarzan propels himself the same way most arboreal primates do, by swinging, climbing, and leaping among the branches. Vines play no special role in this process. An episode late in the book has Tarzan improbably swinging through the not-yet-logged-off but largely vineless north woods of Wisconsin, somehow carrying Jane.
OK, it sounds cool on the page. But no flesh-and-blood human has the musculature to fling himself from tree to tree as monkeys do. That presented a problem when Hollywood decided to portray Tarzan on the screen. Burroughs reportedly felt the answer was Disney-quality animation. Since that wasn't in the cards at the time, the next best thing was circus-style acrobatics using "vines" instead of trapezes. (In the 1932 film Tarzan the Ape Man, starring Johnny Weissmuller, circus performers did in fact execute the trickier vine stunts.) Disney finally released an animated Tarzan movie in 1999; I haven't seen it, but from all accounts the king of the apes catapults through the treetops in a manner that owes a lot more to apes (and is likelier a lot truer to Burroughs's conception) than to Cirque du Soleil.
Still, let's concede one point to vine lovers. Orangutan researchers--and yes, I know orangutans live in southeast Asia, not Africa--speak of a phenomenon called "liana sway," described as "a 'Tarzan'-type movement in which the orangutan swings horizontally on one or more vertical lianas with increasing amplitude to reach the next support" (Thorpe and Crompton, "Locomotor Ecology of Wild Orangutans [etc.]," American Journal of Physical Anthropology, 2005). So to some extent apes can travel by vine--and if the infant Lord Greystoke had been orphaned in Borneo, maybe he'd have learned to do it too.