Tarantula

More than 1,000 species of tarantulas have been identified all around the world!

Tarantulas are among the largest spiders in the world. Many people fear them due to their size and their hairy appearance. However, most tarantulas pose little to no danger to humans. They are reclusive creatures and would much rather avoid confronting a person. Humans are much too large for tarantulas to eat, after all. If given a chance, a tarantula will most likely scurry away to safety, or if cornered, may engage in defensive posturing. In the unlikely event of a bite, most tarantula species are only mildly venomous to humans. Tarantulas are mostly nocturnal. They are prey to many different animals, and they devour many insects, other spiders, and other small creatures in the many different habitats where they live. One of the greatests threats to these fascinating arachnids is overharvesting for the pet trade.

Incredible Tarantula Facts

• Tarantulas live on every continent except Antarctica, but they are most abundant in South America.
• They burrow mainly underground, or under logs or rocks, and sometimes in trees.
• More than 150 genera of tarantulas have been recognized.
• Tarantulas may eat every few days or as little as once a month.
• The largest tarantula has a leg span of up to 12 inches.
• Males live only a short time after mating, but females can live for decades.

Where to Find Tarantulas

Tarantulas live all around the world. They are found on every continent except Antarctica. In North America, most tarantulas range from the southern and southwestern United States throughout Mexico. Likewise, in Europe and Asia these creatures are found primarily in more southern regions. Tarantulas range over most of Africa, Australia, Central America, as well as many islands. More species live in South America than on any other continent.

Tarantulas live in a wide variety of habitats, ranging from the wettest rainforests to the driest deserts. Different species make their homes in savannas, grasslands, prairies, scrublands, and pampas regions. Some species, especially those with arboreal lifestyles, are more at home in rainforests. And some tarantulas thrive in the deserts and the mountains.

Tarantula Burrows

Most tarantulas burrow underground or under rocks or logs. Some hide away in crevices. Others weave webbed burrows in trees. Wherever these reclusive creatures choose to burrow, they do it alone. The only time more than one tarantula will share a burrow is in the first few weeks after they hatch. Then they disperse to make homes of their own, where they live most of their lives in secrecy.  

Scientific Name

Tarantulas belong to the family known as Theraphosidae. Within this family are more than a dozen subfamilies. More than 1,000 different species of tarantulas are currently identified. That is far too many to list individually. Even the genera are too numerous to list here, especially given that so many new species and genera have been identified in just the last few years.

As of this publication, the World Spider Catalog lists 159 different genera within the Theraphosidae family. The most recent addition is the Chinchaysuyu genus from Peru, added in 2023. The oldest genera include Theraphosa, named in 1809, and Avicularia, named in 1818. 

Tarantula Appearance

Tarantulas are large, hairy spiders that come in a wide variety of colors, from browns and grays to electric blues, pink, orange, yellow, and even green. The largest tarantula, the Goliath birdeater, can grow to lengths of 5 inches or more, with leg spans up to 12 inches. This behemoth weighs in at about six ounces, as much as a burrowing owl! Most tarantulas are significantly smaller than that, but they are still quite large, compared to other spiders.

Females of each species are larger than males. Females are generally more colorful than males of the same species as well. This could be in part because tarantulas change in appearance as they molt. Adults usually have more vivid colors and patterns than juveniles, and females, due to their much longer lifespans, will molt more times than males.

Tarantulas have eight hairy, jointed legs and two body parts, the cephalothorax and the abdomen. The cephalothorax is sometimes also called the prosoma, and the abdomen is also known as the opisthosoma. Their eight legs extend from the cephalothorax, as do the pedipalps. Pedipalps look like a shorter pair of legs, extending from the front, near the head. These are used for sensing and for moving things around.

Tarantulas have large fangs, or chelicerae, and a small tube-shaped mouth. They have eight eyes, but only the larger two are easy to spot. These are right up front, on the center of their head. Four more eyes, much smaller, are in a row underneath the two main eyes. And two more eyes lie hidden, one on each side of the head.  

Behavior

Tarantulas basically just want to be left alone. They spend most of their lives either hidden in burrows, under logs or rocks, or in the canopy of trees. They come out to hunt, mainly at night, with a frequency as often as every few days to as little as once a month, depending on a number of factors. The rest of the time, they stay hidden.

These large spiders are independent from just two or three weeks after they hatch. They disperse and live solitary lives, except for mating season, which usually occurs once per year. Mating is brief, if the male is successful in his courtship and avoids being eaten. Males precede mating by emerging, sometimes in large numbers, and setting out in search of females. This is not a true migration, as one might witness in species that move between locations seasonally.

Tarantulas are usually described as slow-moving, deliberate, and docile creatures. They generally do not behave aggressively with the exception of females guarding their young. They do engage in defensive behaviors, such as rearing up on their back legs with their front legs in the air and showing their fangs. If this defensive posturing is unsuccessful in deterring a predator, some tarantula species flick urticating hairs at their attackers. These hairs can irritate or even blind a predator, giving the tarantula a chance to run away and hide.

Diet

Tarantulas eat a wide variety of prey. Essentially, as long as a potential meal is small enough to capture and devour, a tarantula will eat almost anything that crosses its path. Invertebrates, including insects, larvae, other spiders, and all sorts of arthropods make up the bulk of a tarantula’s diet. They also eat small mammals, including mice or voles, and small birds. Many species eat reptiles, including lizards and snakes, as well as amphibians and even small fish.

Unlike many other spiders, tarantulas do not weave webs to catch their prey. They may spin lines of silk that act as tripwires, leading out from their burrows, to alert them to the presence of potential prey or nearby threats. But when it comes to catching a meal, they rely on the tactics of ambush and pursuit. 

Once a tarantula catches an unfortunate victim, it uses its large fangs to disable, kill, and ultimately liquify the prey from the inside out. This is necessary, because it does not have large enough mouth parts to actually bite off chunks of its prey or swallow them whole. Instead, it injects its prey with venom and enzymes that will break down tissues into a soupy liquid. Then it sucks out the liquid with its straw-like mouth and discards the leftovers in a compact ball of waste.

Reproduction

Tarantula reproduction is different from what you might expect, based on other animal species. The mating season usually happens just once per year. After spending the first several years of their lives all alone, males suddenly succumb to the urge to breed. They weave a special mat of silk, upon which they rub their abdomen until they eject a mass of sperm. Then they rub their pedipalps in the sperm, soaking up as much as possible into a pair of structures called palpal bulbs. The sperm will remain viable inside these bulbs until the male is able to mate with one or more females.

Armed with their sperm-loaded appendages, the males embark on a search for willing female mates. Male tarantulas of a species often leave their burrows simultaneously in large numbers, possibly to increase the chances that at least some of them will elude predators. They search for females, following chemical scents and vibrations, until they encounter the silken threads leading to a hidden burrow.

Once a male tarantula locates a female of the same species, he engages in courtship. He approaches and taps on the webbing at the entrance to the burrow. If the male is clumsy in his courtship, or the female is simply too hungry to mate, she may engage in sexual cannibalism and eat the male before he is able to escape.

Fertilization

The successful male mates with a female by engaging her face to face and inserting his pedipalps into the female’s genitalia. He may use special spurs on his front legs to hold back the female’s fangs as he deposits his stored sperm in a sac inside her reproductive cavity. When the mating is complete, he quickly runs away. Although a male tarantula is at greater risk of being attacked and eaten before mating than after, a timely exit is essential. Surviving males may mate with additional females before the mating season is over.

After mating, a female tarantula may retain the sperm sac and her eggs for some time, depending on the species. She will deposit both the eggs and the sperm in a silk cocoon in her burrow. Again, depending on the species, females may lay 50 to more than 2,000 eggs. The female guards the egg sac aggressively for up to nine weeks, turning it occasionally, until the eggs hatch. Then she continues watching over the babies until they disperse two to three weeks later.

Predators

Tarantulas may be frightening to many people, but to a wide variety of animals, they just look like a big, hairy snack. Some of the natural predators of tarantulas include lizards, snakes, large frogs, and birds of prey such as owls, hawks, and eagles.

Mammals, such as opossums, skunks, honey badgers, weasels, coatis, and armadillos easily dig prey out of burrows. This makes them very effective predators of tarantulas. Other mammalian predators include canine species such as coyotes and certain foxes, along with felines such as ocelots, jaguars, lynxes and more.  

Other arachnids such as larger tarantulas and scorpions, along with arthropods such as centipedes, crabs, and various insects prey on tarantulas.

Perhaps the most horrific predators, though, are wasps. Tarantula hawks, wasps of the Pepsis genus, attack tarantulas with a venom that paralyzes but does not kill. The female wasps sting their prey, and once they immobilize the tarantula, they drag it back to a prepared burrow and stuff it inside. The wasp deposits an egg on the body of the tarantula, seals the burrow and leaves in search of more prey. The egg soon hatches and the larva begins to devour the defenseless tarantula.

Lifespan

Female tarantulas can live a very long time. Depending on the species, females may live 40 years or longer. Males, on the other hand, live only about 5 to 10 years. Once they reach sexual maturity, they survive only about another 12 to 18 months at most. Many are eaten during their search for a mate. The ones that do survive their mating season rarely survive the next molt.

The IUCN Red List for Threatened Species lists many tarantulas as species of least concern. These have relatively stable populations and sufficient numbers and ranges such that they do not require intervention. Some, however, are much less common with populations that are in serious decline.

Species such as the stunning orange and black Mexican Fireleg, or Brachypelma boehmei, the Mexican Orange Beauty, or Brachypelma baumgarteni, and the Mexican Blackvelvet, or Brachypelma schroederi, all native to Mexico, are classified as endangered. Likewise, the Asian tarantulas, Poecilotheria formosa, Poecilotheria rufilata, and Haploclastus kayi. These are all endangered due to habitat degradation and overharvesting for the pet trade. Species such as Nesiergus halophilus and Nesiergus gardineri, endemic to the Seychelles islands, are listed as critically endangered. Their threats include invasive species and the loss of coastal habitat due to rising sea levels.

1. World Spider Catalog, Available here: https://wsc.nmbe.ch/genlist/100/Theraphosidae
2. Nelson Ferretti, et. al., Available here: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4202319