Stalking Spiders

Tarantulas reveal intriguing mammal-like behaviors, says a scientist who cares enough to study them (not to mention keep 500 of them alive in his lab)

By James Balog, Sy Montgomery|Thursday, February 05, 2004
RELATED TAGS: ANIMAL INTELLIGENCE
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When threatened, the Usambara orange tarantula can get very aggressive. It rears up, slaps the ground, hisses loudly, and even drips venom from its fangs. “They don’t try to bite very much,” says arachnologist Sam Marshall. “It’s really just a display.”

Sam Marshall doesn’t waste much time. Seconds after stepping into the steaming rain forest of French Guiana, he announces his agenda: “Let’s divide and search for holes with big, hairy legs.”

After all, he hasn’t come to French Guiana for the beaches (muddy and shark infested), the food (cheese, bread, and sardines), or the shopping (none, but credit cards can be used to dig out ticks). He has come for the tarantulas—tarantulas that are big enough to eat birds.

French Guiana, best known for the notorious Devil’s Island penal colony, is the tarantula capital of the world. The size of Indiana, this South American protectorate hosts at least a dozen species, including the world’s largest, Theraphosa blondi, the goliath birdeater. To Marshall, an assistant professor of biology at Hiram College in Ohio, the jungle here is a little bit of heaven. Within minutes, the 45-year-old arachnologist is lying blissfully on his belly, poking a twig down a foot-long tunnel. “Come out!” he calls into the tunnel. “I want to meet you!”

Marshall’s freckled face is inches from a fist-size hole inhabited by a quarter-pound tarantula. Make that an angry quarter-pound tarantula. With a walnut-size abdomen and a head as large as a 50-cent piece, the goliath birdeater has a 12-inch-wide leg span that could cover your face. Or in this case, Marshall’s face.

“Oh! Now she’s kicking!” Marshall says as he shines his headlamp into the hole. “She might be kicking hairs! Can you hear her hissing?”

A rasping sound comes from the hole. But Marshall holds his ground. A few seconds later, he wishes he hadn’t. His face is itching and burning. The goliath birdeater has used her hind legs to kick microscopically barbed hairs off her abdomen. They ended up in Marshall’s face, irritating his skin, eyes, and nose. Despite its size, the goliath isn’t deadly to humans, but its defense mechanisms are more than unpleasant.

For Marshall, a face full of tarantula hair is part of the job. And before long he’s back looking into the same hole. So little is known about the goliath that despite its name (bestowed because an early specimen was recorded feeding on a songbird), nobody actually knows what it normally eats. Only twice has the species been seen making a kill in the wild—once an earthworm, another time a caecilian, an amphibian. To Marshall, such ignorance is indicative of what’s wrong with arachnology. “Here we have the biggest of something in the world, and nobody studies it!” he says.

Despite the growing number of humans who seem to enjoy keeping tarantulas as pets, the spiders are mostly a mystery. Marshall is one of only a dozen arachnologists worldwide specializing in them—and the only scientist who runs a lab full of tarantulas gathered from around the globe. He is also the only scientist who has written a popular book about the creatures: Tarantulas and Other Arachnids: A Complete Pet Owner’s Manual. “It’s a pretty huge unfilled niche that he’s in,” says Jonathan Coddington, an arachnologist at the Smithsonian Institution.

Scientists have long dismissed tarantulas as too primitive to exhibit interesting behavior. Arising 150 million years ago from a smaller, hairy ancestor, the creatures retain such primitive characteristics as fangs that move up and down instead of sideways, and they don’t weave webs. In his Biology of Spiders (1982 edition), German arachnologist Ranier Foelix barely mentions tarantulas. “Not long ago,” wrote English biologist T. H. Savory of Malvern College, “the spiders were the most neglected of the most interesting animals.”

Another reason for the neglect has been the tarantulas themselves. They are more difficult to study than common garden spiders. They tend to live deep in sometimes-twisting holes in the sweaty tropics, they’re too big to fit under a microscope, and females can live for 30 years, making for long time frames between generations and slow captive breeding.

Marshall, son of the late actor E. G. Marshall, is changing that—and at the same time, he hopes, the tarantula’s image as the bloodthirsty villain of grade B horror films. He says part of his job is to “de-demonize these spiders. They don’t have a bloodlust to bite people. They’re just little fuzzy creatures, and if you handle them correctly, they’re harmless. I just basically make them seem like interesting animals rather than some horrible creature.”

His studies have revealed a surprising aspect of the breed: Tarantulas share many behaviors with mammals. Like most spiders, they seem to be solitary cannibals, so intolerant of company that some females snack on their suitors. But others tenderly care for their young, and tarantula families sometimes share food. Mother tarantulas are known to go without eating so that their offspring can eat. Muses Marshall, “Who’d have thought that the world’s scariest spider would have family values?”

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Sam Marshall holds a pinktoe tarantula he found on a tree in French Guiana. The spider is docile but its hairs are irritants.  Marshall’s hand itched for days after this picture was taken.

Still, spiders are not hamsters, and on the door of his lab at Hiram College’s J. H. Barrow Field Station, 20 miles southeast of Cleveland, Marshall has posted rules for visitors: “Do not open or move any container. Many tarantula species are very fast and aggressive and will bite. Accidentally releasing a tarantula could end badly for both you and the spider. Please don’t take any unsupervised tours!” But Marshall is happy to supervise visits and proudly declares, “This is the only comparative tarantula lab that is global in reach.”

To prove it, he points out a silver and black Heteroscodra maculata, originally from Cameroon, that resides in a wide-mouthed plastic coffee jug marked “USE EXTREME CAUTION” and “POTENTIALLY DANGEROUS.” In a glass jar that once held 155 pieces of watermelon-flavored taffy, he has restrained an iridescent Avicularia metallica, collected off a tree at a rest stop along Route 1 outside Cayenne, French Guiana.

There are Tanzanian chestnut tarantulas in plastic food tubs, and baby blonde-leg tarantulas in potato-salad deli cups. Marshall says his spiders are comfortable. Few tarantulas roam widely, preferring to live out their lives almost entirely within inches of their burrows. “You can say tarantulas are agoraphobics,” he said. “See how they live in the wild: one foot in a tidy, snug hole. Tarantulas just do their thing, whether they’re in a plastic container from Wal-Mart or on the side of a tree in South America.”

All in all, there are about 500 live tarantulas in a room the size of a spacious kitchen. Many of them were originally housed at Marshall’s house, where he kept “a big collection” of tarantulas for a number of years. How big? “Hundreds,” he answers. “Hundreds. Hundreds.” During his postdoctoral years at Miami University in Ohio, he had a two-bedroom apartment—“one people bedroom, one tarantula bedroom.” He had already married a fellow arachnologist, Maggie Hodge, who clearly did not mind spiders. She did not, however, like the rattlesnake that was living in his closet when they met at the University of Cincinnati.

Marshall’s course in life was set in his teens—possibly from the moment he saw his first tarantula in a tank on the desk of a U.S. Park Service ranger in New Mexico. “I saw that and thought it was the most amazing thing,” says Marshall. The large spiders soon joined the menagerie of exotic poultry, turtles, snakes, monitor lizards, and falcons he kept in sheds behind his parents’ house in Mount Kisco, New York, and in their labyrinthine basement. When he was an undergrad at Bard College in New York, tarantulas shared his dorm room with a hawk, ferrets, a monitor lizard, and a ball python. (The dean of students made him move his scorpions to the biology department.)

“I think of myself as a xenophile,” Marshall says. “I was drawn to things that are different.” And what could possibly be more different than a tarantula—a big, hairy spider who wears her skeleton on the outside, who smells and tastes with her feet, and whose fanged, eye-covered head is also endowed with eight legs, two arms, and a sucking stomach?

Tarantulas are far less dangerous to humans than other spiders, such as the black widow. No tarantula’s venom is toxic enough to kill a human, and they seldom bite. But they shed their hairs—projections on the exoskeleton called setae.

Although tarantula hobbyists have endured the hairs for decades, the details of their use for defense were not studied until the 1970s, when researchers discovered that some of them seem to be designed to defend against a single species. The hairs of the Mexican blonde tarantula, for instance, are adapted to irritate only the nasal passages of the grasshopper mouse—a job they do so well that they can kill the rodent.

So far, seven structurally distinct types of defensive hairs have been recognized; Marshall discovered one of those and found new uses for several others. Some species, for example, shed clouds of golden hairs from their mouths; others shed from their bellies. One sheds hairs onto egg sacs to protect its young from predators and parasites. The goliath birdeater, Marshall found, uses its hairs to create a special silken mat on which it lies upside down when molting. But perhaps the most original use to which tarantulas have put their copious hair—including the goliath birdeater—is to make noise.

The goliath makes the loudest sound of any spider—a hiss audible from 10 feet away and designed to scare off predators. Marshall discovered that the noise comes from a scrubbing motion the tarantula makes with the two food-handling arms at the front of its head and the first two pairs of its walking legs. The noise sounds like strips of Velcro being ripped apart and is created in much the same manner—by entangling the microscopic hooks of one set of leg hairs with the filaments of another and pulling them away from each other.

Marshall’s discovery was confirmed in a series of ingenious experiments. In one, his collaborator Ellen Thoms at the Cincinnati Zoo spray-painted molted tarantula exoskeletons gold to prepare them for study under an electron microscope, which revealed the fine structures of the hooks and filaments. In another experiment, Marshall shaved the legs of one of the giant arachnids. He knocked out his subject with CO2, removed some hairs with a razor, revived the beast, riled him, then listened for hissing. Then he shaved a little more. When the hissing stopped, he knew he had hit the right hairs.

The experiments went well beyond understanding the hairs themselves. They show that tarantulas evolved profoundly and rapidly to adapt to ecological challenges—unlike such living fossils as horseshoe crabs, which have remained unchanged for millions of years. The great challenge for tarantulas was probably the sudden appearance of burrow-dwelling, spider-hunting mammals, the forerunners of today’s skunks and possums. “Some tarantula ancestor evolved the urticating hairs, and it just went woof! It just took over,” Marshall says. “It’s one of the greatest evolutionary tales you can tell.”

Urticating hairs—those that provoke itching—evolved only in New World tarantulas, which reside in areas ranging from the South American tropics to as far north as Rolla, Missouri. About 500 of Earth’s 850 tarantula species live in the Americas. Of those, 460 have urticating hairs.

In the tropics, the hairs are not the perfect defense against the coatimundi, a long-snouted relative of the raccoon that can move fast enough to avoid the hairs. Wasps are another problem for tarantulas. Several varieties paralyze tarantulas with their sting and then lay eggs in the spider’s abdomen. When the eggs hatch, the paralyzed spider is eaten alive by wasp larvae. Even the goliath birdeater is not immune. The particular species of wasp that feeds on the goliath is the size of a sparrow.

Elsewhere, tarantulas without hairy weapons have had to make do with aggression. Marshall says tarantulas from Asia, Europe, Australia, and Africa can seem nasty-tempered. He tells a story about one tarantula in Australia that reared up and, waving its legs and gnashing its fangs, chased away a dog. Although a tarantula can’t kill humans, “the venom of Australian tarantulas is deadly to dogs,” Marshall says. “It’s one of those flukes of venom.”

 When it’s feeding time at the spider lab, Marshall uses tweezers to seize a cricket hopping around the food terrarium, opens a tarantula container, and drops in the insect. The spider gravitates to it like metal to a magnet, then begins to chew and suck its food.

Although tarantulas are such eager eaters that they often eat each other, Marshall found that a female Tanzanian chestnut tarantula will put down its freshly killed prey and allow its young to feed instead. “They appear to sacrifice for their offspring,” Marshall says. “They defer eating themselves. They become anorexic. While the babies get fat, the mother shrinks.”

What’s more, some tarantula young appear to cooperate with one another at mealtime. With most spider species, the young push their siblings away from food. But in the Cameroon red tarantulas that Marshall describes in a forthcoming paper, spiderlings not only feed side by side without aggression but with their legs woven together. When Marshall saw this he realized: “They are huddle-feeding together. This is cooperation!”

A Memphis Zoo colleague, Steven Reichling, recorded a similarly striking behavior in a related species of African baboon spider, Hysterocrates crassipes. He noted that a female spider faced with another mother’s hungry babies did not try to kill or injure them—even when they annoyingly crawled up her legs and tried to eat her meal. In the company of suitors, females of this species also exhibited remarkable restraint: A male survived in a female’s enclosure for two months without being cannibalized and finally was removed without incident.

Even more surprising, in a presentation at the Ohio Academy of Science two years ago, two of Marshall’s undergraduate students demonstrated that Indian ornamental tarantulas—fast, high-strung spiders with bright black-and-yellow markings on their forelegs—usually choose to live with a sibling. Melissa Varrecchia and Barbara Vasquez offered 20 11-month-old tarantulas a choice of retreats: a tube in which a sibling had spun silk or an identical empty one. Fourteen chose their sibling’s tube.

Under Marshall’s tutelage, another undergraduate, Amanda Wiegand, discovered that an inch-long East African tarantula performs an elaborate courtship dance in which both the male and female participate. The male twitches and drums his legs, and the female responds by gracefully fanning her legs. The dance continues for several minutes before ending in copulation. It is the first case of tarantula courtship described by scientists.

Such findings have changed Marshall’s entire view of spiders. A year and a half ago he told a radio interviewer that the scientific paradigm he was taught for the life of a spider was simple: “They hatch, they grow, they live in the eternal now moment, and there’s really no role for experience shaping their behavior—they’re like little machines.” Now he has watched them for too long to believe that. “I’ve repeatedly seen tarantulas respond to my entering a room by moving to a different part of the cage or going into a retreat,” he says. “When you walk in the room, they know: Here comes this huge thing again.”

Furthermore, individual tarantulas exhibit individual quirks. “I’ve brought a lot of Theraphosa out [of the jungle] and into captivity,” Marshall says. “Some would settle down and adapt to the artificial habitat of a terrarium with a cave I provided, while others would pace and pace. It’s very clear to me that individual spiders can differ in how they respond to stimuli.”

Tarantula hobbyists have reported similar observations. One told Marshall how a tarantula methodically sorted the multicolored aquarium gravel in its tank into separate colors. Another had a female tarantula who learned to unscrew the lid to her container. He found her two days later in a stack of folded laundry.

Personality is a heavy word to put on a bug,” Marshall says, “but if you define personality as individual behavior responses—well, I’ve had some spiders, tarantulas of the same species and from the same population, and I can take one out of a box and let it run over my hand, and I have others that just freak out and try to run away. A lot of that is individual variation in how they respond to being touched.” Still, he is not sure how far he can go with this notion. Tarantulas, he ponders, “probably know something about the area where they live, the landscape they live in, at some spidery level that we can only guess at. Long-lived, giant spiders have a lot more going on than we have any idea of.”

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