March 2010

Tarantula!

Texas’ most fearsome-looking spider is actually a gentle giant.

By Dale Weisman

Misunderstood and maligned by many, tarantulas — like bats, scorpions and snakes — often get a bum rap. After all, they’re big, hairy, creepy-crawly spiders that are stealthy nocturnal predators. For arachnophobes, they’re bug-eyed monsters from our worst Halloween nightmares.

From Texas to Timbuktu, tarantulas suffer from bad press. Blame it in part on sensational movies like the 1955 sci-fi flick Tarantula, in which Clint Eastwood, playing a fighter pilot, napalms a giant, rampaging mutant spider, or the mega-hit Raiders of the Lost Ark, in which menacing tarantulas crawl across Indiana Jones’ back in the opening scene. Real-life tarantulas, of course, bear no resemblance to the malevolent creatures portrayed by Hollywood. Despite their fearsome looks, tarantulas are gentle giants, reclusive by nature, harmless to humans and an essential part of our ecosystem.

“Tarantulas are not as dangerous as many believe,” says Rick West, a freelance scientific consultant from Canada and one of the world’s leading authorities on tarantulas. Having spent 45 years studying tarantulas in their natural habitats in 27 countries, West knows from experience. “To date there has never been a proven human fatality directly resulting from the bite of a tarantula,” he says.

Tarantulas abound in Texas, from the Rio Grande Valley and coastal plains to the prairies and Pineywoods to the Hill Country and Trans-Pecos. Texans frequently encounter tarantulas around the yard and in the wild. Yet bite incidents are rare (and no more painful than a bee sting) and occur only when someone is harassing or mishandling them.

Despite their undeserved bad reputation, I believe tarantulas have more fans than foes. When I posted my interest in tarantulas on Facebook, I received only one “ewww, spiders!” reaction amid several favorable comments (“cool, aren’t they?”) and interesting anecdotes.

Tarantula societies, such as the American Tarantula Society (www.atshq.org), add to our enlightenment and spring to the defense of these fascinating arachnids. Many tarantulaphiles, from curious kids to serious arachnologists, keep tarantulas as terrarium-dwelling pets, as beloved as Fido in some households. For nature lovers in general, tarantulas hold a special mystique as the largest, heaviest spiders on the planet and “megafauna” of the bug world.

Tarantulas are ancient arachnids, as old as dinosaurs. According to West, fossil records show that tarantulas have been crawling around, virtually unchanged, for more than 20 million years. The oldest known ancestral tarantula-like fossils date back 235 million to 240 million years.

“Tarantulas have figured in indigenous creation stories and fanciful myths throughout the world,” says West. The Nahua peoples of central Mexico, for example, called tarantulas Tlalueuetl. “Tlal” comes from the word tlalle, which means “owner of a big piece of land,” and “ueuetl” means old. Think of tarantulas as “the old owners of a big piece of land.”

In a few countries, such as Cambodia, tarantulas provide a nutritional food source (approximately 63 percent protein by body weight). Tarantula venom also has shown promise as a cure for heart arrhythmia and Parkinson’s and Alz-heimer’s diseases, as well as for use in natural pesticides.

Tarantulas are not considered to be true spiders by biologists. Rather, these spiders belong to a smaller, more primitive group called mygalomorphs. A big difference between the two groups is that mygalomorphs do not produce elaborate webs composed of sticky silk for prey capture. Mygalomorphs account for only about 7 percent of the world’s spider species. Other notable mygalomorphs include purseweb and trapdoor spiders.

The word “tarantula” stems from an Old Italian word tarantola, derived from the southern Italian town of Taranto, home to the European wolf spider (Lycosa tarentula).

During the Renaissance, local peasants believed that Lycosa bites caused a disease called tarantism, cured only by a frenzied dance, the tarantella _ a good excuse for wild abandonment during an age of religious repression.

When European explorers encountered mygalomorphs in the New World, they called them tarantolas, and over time the familiar name “tarantula” stuck. Tarantulas also came to be called “bird-eating spiders” when naturalists and scientists exploring South American jungles reported seeing enormous mygalomorphs feeding on small birds. (The world’s largest tarantula _ the Goliath birdeater [Theraphosa blondi] _ has a nearly 12-inch leg span.)

Found in the tropical and subtropical regions of the world, tarantulas range from North, Central and South America and the Caribbean to Africa and the Middle East to southern Asia, the Indo-Pacific and Australia. In the United States, they flourish west of the Mississippi River and as far north as parts of Missouri, Utah and central California.

Tarantulas live in diverse terrestrial and arboreal habitats: deserts, prairies, scrub forest, jungles and rain forests. Terrestrial tarantulas reside in burrows (often of their own making, though sometimes borrowed from rodents), in crevices and deeply cracked soil, and under rocks and logs, while arboreal species in the tropics live in trees.

The 2009 World Spider Catalog (from the American Museum of Natural History) lists 920 known tarantula species. The online catalog also tallies 40,998 known spider species, so tarantulas account for almost one out of every 40 species of spiders. As arachnologists discover new tarantulas and other spiders, the species list will continue to grow each year. Tarantulas are quintessential Texas natives. The latest published research identifies 14 species in Texas. Dave Moellendorf, an Austin native and noted authority on Texas tarantulas who has studied them for more than 30 years, believes that the number of Texas tarantula species may be considerably smaller _ perhaps only eight species

According to Moellendorf, morphological features may mean little in identifying tarantula species, and several species actually may be members of the same species with varied morphology.

“My favorite Texas species is the Rio Grande gold,” says Moellendorf. “It’s one of the most beautiful species native to the United States, and I am proud that it is a Texas spider.”

Tarantulas of the genus Aphonopelma flourish not only in Texas but also in neighboring states and parts of Mexico. Commonly found in grassland burrows and under logs or stones, they can attain 6-inch leg spans and weigh more than 3 ounces. The hefty, dark-brown tarantulas have been popular as low-maintenance pets because of their docile, easy-to-handle behavior.

Like all arthropods, tarantulas are invertebrates with exoskeletons. A tarantula’s two-part body, consisting of a prosoma (cephalothorax) connected by a narrow stalk called the pedicel to an opisthosoma (abdomen), is similar to those of other spiders, but larger and hairier. In addition to eight legs, a tarantula prosoma has additional appendages: two chelicerae (mouth parts) with large fangs to inject venom and a pair of pedipalps that aid in sensing, digging and food handling. The pedipalps of male tarantulas contain specialized bulbs (visualize tiny turkey basters) used to hold semen for reproduction. Similar to other spiders, tarantulas periodically shed their exoskeletons through a molting process as they grow and mature. Young tarantulas molt several times a year, while adults molt about once yearly. Amazingly, tarantulas can regenerate lost limbs through successive molts.

Tarantulas prey on nearly any creature small enough to overpower. After their injected venom and digestive juices liquefy their prey, they suck up dinner with a straw-like mouth and sucking stomach.

Insects make up the majority of their prey. Texas tarantulas feed primarily on crickets, June beetles, ground beetles, grasshoppers, cicadas and caterpillars. Some large tarantulas feed on small rodents, lizards, snakes _ and yes, small birds. Opportunistic cannibals, tarantulas even eat each other.

Lacking keen eyesight, tarantulas detect prey and threats through sensitive hairs covering their bodies. Most New World tarantulas (those dwelling in the Americas) have an unusual defense mechanism. When threatened, they use their back legs to flick a cloud of urticating (irritating) hairs from their abdomen. The hairs can cause painful skin rashes and excruciating lung and eye injuries. (Urticating tarantula hair once served as an ingredient in itching powder sold in novelty stores, although current formulas use pepper and fiberglass as irritants.)

Old World tarantula species (those from Africa and Asia) lack urticating hairs; however, they compensate with more potent venom and defensive behavior. When threatened, most tarantulas rear up in an impressive display, lifting their front legs and spreading their fangs. Some large tropical species can produce a loud hissing noise by rubbing together modified hairs found between the base of their legs, a behavior called stridulating.

Tarantulas have few enemies in the bug world. In Texas and the Southwest, their foremost predator is the tarantula hawk, a large, dark-blue wasp with rust-red wings. After stinging a tarantula, the wasp drags its paralyzed prey into a burrow and lays an egg on its body, and the emerging larva feasts on the spider.

Tarantula species have varying life spans in the wild. According to Moellendorf, the life span of Aphonopelma anax (a South Texas species) extends up to 25 years for females, but only six to eight years for males. Destined to mature, reproduce and die young, male tarantulas typically live about one-third as long as females.

Tarantulas, like other spiders, spin silk. Some terrestrial tarantulas line their burrows with silk and, during the day, cover the entrances with a silken veil. Some jungle-dwelling arboreal tarantulas build their nests entirely of silk. Female tarantulas produce silk to create an egg sac. Males create silk webs as a temporary depository for sperm before setting off to find a mate.

Tarantulas in Texas and other locales seasonally “migrate,” although their en-masse movement is not a true migration, explains Moellendorf. After male tarantulas have completed their final molt, they embark on a search for females so that they can reproduce before they die _ often only a few months after they mature sexually. It may take a male tarantula three to seven years to mature, and then he begins wandering, leaving his familiar burrow behind.

According to Moellendorf, Texas brown tarantulas, as well as other Trans-Pecos species, often wander in droves across roads and countryside at dawn and dusk in May through July and again in September through November. They are looking for love: receptive females.

I witnessed this spectacle of nature one July morning while riding a motorcycle down a lonely highway threading from Pecos to Bakersfield. At first, I noticed a few tarantulas crossing the road. Mile after mile, a few became hundreds, and this parade went on for 50 miles. Slowing down and weaving down the blacktop, I did my utmost to avoid squashing them.

Car and motorcycle tires are the least of the many perils that tarantulas face. “Tarantulas have survived scores of natural enemies and global changes,” says West. “Now, with the heavy use of pesticides and agricultural, industrial and urban development that transforms the tarantula’s habitat, tarantulas face their biggest threat _ man.”

Ultimately, tarantulas deserve respect and concern rather than fear and indifference. “Tarantulas are an integral part of our world and form one of the threads of balance in the greater web of life,” concludes Moellendorf. “Just like a spider’s web, if a strand is broken or removed, the rest may unravel, and whatever happens to tarantulas will affect us in some way. All things are connected.”

The Ethics of Capturing and Keeping Tarantulas as Pets

Many arachnophiles keep tarantulas as pets in terrarium environments. Tarantulas require very little maintenance other than a steady diet of live crickets and other insects. Enthusiasts consult websites (such as www.arachnophiles.com or www.arachnoboards.com) and guidebooks (such as the excellent, comprehensive book, The Tarantula Keeper’s Guide). Exotic pet stores sell popular tarantula species, including some from Texas, but think twice before adopting unusual or rare tarantula species or those captured from the wild.

“Many stores acquire spiders from the wild, so ask whether one is purchasing a captive-born specimen or a wild-caught one,” advises Dave Moellendorf. “There are enough tarantula breeders raising exotic and native species in captivity that they should not be taken from the wild unless they are in danger of being bulldozed by development or exterminated in some other fashion, and also only if there is no other safe place to release them within their native habitat.

“Texas tarantulas often found wandering across the countryside are normally short-lived males that will not make good pets,” adds Moellendorf. “They are generally nervous and want to complete their life cycle. There’s nothing wrong with, say, catching a male, studying it and then putting it back into the wild so he can complete his life cycle. Females make for better pets, but all should be left alone as the rate of human expansion is already creating stress on their environments. If we are not careful, they will begin to disappear.”

Rick West concurs: “From an ethical standpoint, wild animals should never be taken from their environment and kept as either pets or novelties to impress or scare other people. Tarantulas, like any other animals, are sentient creatures that have a specific place in their habitat _ primarily keeping the population of noxious pests from overpopulating.”

Some tarantula hobbyists argue that large populations of tarantulas across Texas and the Southwest, as well as other parts of the world, are being plowed up and destroyed by agricultural and urban development. “So what’s wrong with collecting and keeping a few?” a well-intentioned arachnophile might ask.

“This is an age-old argument between plant or animal hobbyist and conservationists,” says West. “If a person is going to remove a living organism from their natural environment and keep it in captivity, I strongly advise they assume the role of responsible stewardship. First, learn about that organism’s optimum care and keeping. Second, keep the tarantula in the best escape-proof environment possible.

“In reality, and sadly, many mature tarantula species are taken both legally and illegally from their country of origin. Even though many countries have enacted laws to protect their tarantulas, this does not stop illegal collectors and tarantula smuggling.

“Some progressive countries allow government-regulated locals to collect small numbers of mature tarantula, breed them in captivity and export only the young produced by captive breeding. This seems to satiate the demand of the pet trade, as well as reduce the poaching of wild tarantulas. However, the biggest threat to tarantulas remains human encroachment and the loss of their habitat.”

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