- ABOUT US
The Odd Couple
During its 30-year lifespan, a female Oklahoma brown tarantula may share a burrow with a succession of Great Plains narrowmouth toads.
Illustration by JJ Ritchey
Two unlikely roommates share a burrow in a partnership as surprising as it is mutually beneficial.
By Gordon Grice
Illustrations by JJ Ritchey
Published January/February 2013
It’s a hard world for frogs. What happens in my son’s terrarium happens in the wild, too, and tarantulas aren’t the only predators a frog has to fear. So frogs have developed an array of defenses. Some hide in the mud. Some have coloring that allows them to blend in with the bark. Some climb trees. Some feed on toxic beetles so that they themselves ooze toxin. And some cultivate friends in low places—friends who ought to find them delicious.
Take the Great Plains narrowmouth toad (Gastrophryne olivacea). You can find this species in most of our state. Actually, you probably can’t find it; it’s likely hiding under logs and dead leaves or in something else’s burrow. It’s a tiny frog, topping out at about an inch-and-a-half long. At rest, it might be mistaken for an angular dollop of mud, the kind you’d find on a truck’s fender after it’s driven down a wet Oklahoma country road.
Its needs are humble; it mostly eats the insects others find too troublesome—ants. Ants are tiny, they sting and bite, and they’re mostly indigestible exoskeleton, so you’d have to eat a lot of them to make it worth your while. But the narrowmouth is up to the task. Its skin exudes a mild toxin that discourages the ants from counterattacking it. Special flaps of skin twitch the ants away from its eyes. It can sit on an anthill licking up its prey with its gluey tongue.
One predator that can’t handle ants is the Oklahoma brown tarantula (Aphonopelma hentzi). You have probably seen these large arachnids—the males, anyway—scurrying across the roads each autumn, looking for love. (Females of the species tend to spend most of their time in their burrows.) In some spots, they briefly become more common as roadkill than skunks or bull snakes.
Remember those big tarantula fangs? They’re lousy for gripping tiny pests. I’ve seen an Oklahoma brown wander near a nest of black ants the size of pepper flakes, only to bounce out like it stepped on a hot griddle. But that doesn’t always help, because some ants go scouting for food even below the surface, into the burrows of creatures like the tarantula.
A tarantula’s burrow is a small hole or crevice lined with the tarantula’s silk. It may be an old chipmunk den or the space under a rotten log. In cross section, it looks like a buried sock. Inside this burrow, the tarantula lies in wait, listening for the footfalls of prey. A slight vibration will bring it spilling out of the burrow to attack.
Otherwise, it wants to be out of sight of its own predators, like birds and raccoons. But the burrow is little help against some ants. They’re small enough to penetrate it and devour the tarantula’s eggs and even its hatchlings.
Unless, that is, the burrow also accommodates a narrowmouth toad. Not many animals get into a tarantula’s burrow without provoking it to action, and indeed, when a narrowmouth enters, the tarantula places an inquiring foot on its head or back.
This is where something unusual happens. The tarantula ought to eat the toad; it eats other toads. This time, however, it doesn’t.
Whatever information its sensitive foot gathers must satisfy it that the toad is a friend, because it lets the narrowmouth in. Once installed, the narrowmouth eats any invading ants. It will even defend the spider’s eggs and young. Obviously, the frog benefits from these arrangements because it gets to eat the ants, but it probably gets another benefit: The tarantula kills or intimidates frog-eating predators like snakes, birds of prey, and bigger frogs.
Many living things—perhaps most—depend on some sort of teamwork. Fungi extend the roots of trees, ravens help wolves find food, and people and dogs hunt together. Over the last thirty years, scientists have found arrangements similar to that of the Oklahoma brown tarantula and the Great Plains narrowmouth toad between spiders and frogs in Sri Lanka, India, and Peru, with the odd couple sometimes cohabiting in the hollows of trees.
But I like our Oklahoma brown and narrowmouth toad the best, because they are so humble in their colors, so lacking in pretense. They’re an example to us all, dwelling in the soil beneath our very feet.
Back | 1 | 2 |
Nature writer Gordon Grice is the author of two critically acclaimed books, The Red Hourglass: Lives of the Predators (1999) and The Book of Deadly Animals (2011). A native of Guymon, he lives in Wisconsin, where he teaches at the University of St. Thomas and in the UCLA Extension Writers’ Program.