You know what’s been on my mind lately? Midgets. Well, dwarfs. Well, actually, pygmies. I’ve been considering a post about pygmy animals for a while, and as luck would have it, a research team in Borneo just found this miniscule marvel:
Yes, that’s an adult frog. (If it weren’t, it’d be a tadpole, silly.) Measuring only 12 mm, the male Microhyla nepenthicola is the smallest frog in Europe, Africa, or Asia — though, amazingly, there are two species in the Americas that are even tinier. M. nepenthicola‘s species name comes from the Nepenthes pitcher plants it inhabits to keep its skin wet. It might never have been found if it weren’t for its loud, rasping call, which conjures for me an image of a puzzled biologist putting his ear to a pitcher plant like a dog to a Victrola gramophone, wondering why it was croaking.
As megafauna ourselves, I think most humans have this idea that species are trying to evolve to be larger, but are somehow limited. But the fact is that being small has its advantages, and many species are more than willing to become miniaturized to seize the opportunities that can only be found once you breach the microcosmos.
I’ve written before about insular gigantism, by which animals on islands can reach unusually large sizes for their genera. But islands have a sort of Wonderland effect on animals that fall down the rabbit hole and find themselves there by accident: one pill makes you larger, and one pill makes you small. (And the ones your mother gives you don’t do anything at all.) While a bird, bug, or reptile might reach an extraordinary size on an island, a mammal or amphibian might actually shrink to fit the reduced resources that ecosystem has to offer, a phenomenon called insular dwarfism. Take, for example, the dwarf elephants that lived on Mediterranean islands such as Sicily, Crete, and Cyprus, or the so-called “Hobbits,” or Homo floresiensis, an extinct teacup humanoid from an island in Indonesia.
Or how about the Dwarf Chameleon, found only on Nosy Be, a small island off the coast of Madagascar. It takes an island off an island to shrink something this small.
Or the Barbados Threadsnake, the world’s smallest snake, only four inches long and as thick around as a strand of spaghetti.
But the limitations of islands aren’t the only reason a species might become, to borrow a term from Halloween candy, “fun-sized.” For one, size usually correlates surface-to-volume ratio, which makes larger animals better at retaining heat and smaller animals better at dissipating it. Take the example of hummingbirds: the Giant Hummingbird, the world’s largest and nearly the size of a sandpiper, lives in the cold Andes, while the bee hummingbird, the world’s smallest bird, lives in the hot tropics of Cuba. (Which, admittedly, is also an island.)
But the biggest advantage to smallness is simply that the smaller you are, the bigger the world becomes. There’s a ceiling to how large most animals can get; if the world were populated by giants, there simply wouldn’t be enough food to feed us all. But if you shrink, the possibilities are endless. The wilderness is full of much smaller wildernesses, micro-wildernesses, under the leaf litter and in the riffling pools of a hot spring. A fallen tree can be a mountain range, and blood can be an ocean of rivers, and with the change in dimension, the world becomes full of feasts and plenty. This is the world on a fractal scale again, ranging from the infinite to the infinitesimal, and with each turn on the microscope, you enter a new niche to exploit and explore. We live on a planet of precise size inside a universe of certain dimensions, but a world can be defined best by subjective experience, and by that measure, there are infinite worlds within our world.
I’ll leave you with one last animal, and a final question: If vertebrate animals are ultimately limited in how large they can evolve to be, what’s to keep them from shrinking into the microscopic? Could there someday be a frog that would be impossible to see with the naked eye? I can guess at a few physiological governors: surface-to-volume ratio, the heart rate needed to sustain something so small, the supernaturally fast metabolism. For example, the Etruscan shrew, one of the world’s smallest mammals, has a life expectancy of 15 months. Its heart beats an astounding 14 times a second. Another danger to small vertebrates is simply that small changes in our macro space can have huge effects in the microcosmos. The world’s smallest mammal, Kitti’s hog-nosed bat (also called the bumblebee bat), lives on the mainland in the limestone caves of Thailand and Burma. Only discovered in 1974, it is already reaching critical endangered status because of habitat disturbance. I wonder how many more species we haven’t discovered yet because they live underfoot and because we are god-like and yet astoundingly near-sighted, species we’ll only find when our giant machines have easily leveled their worlds, species who we’ll only find when they’re clinging to our thumbs for dear life.