goliath birdeater

goliath birdeater, (Theraphosa blondi), South American tarantula that is widely considered to be the largest known arachnid by mass. The goliath birdeater is found in the Amazonian rainforests of northern South America, its range stretching from Venezuela to northern Brazil. Despite its common name, the superlative spider rarely eats birds. Like most of the world’s invertebrates, the conservation status of the goliath birdeater has not been assessed by the IUCN Red List of Threatened Species.

Physical description

The goliath birdeater is brown or black in color and covered in hairy bristles, including stinging, or urticating, hairs. As a spider, the goliath birdeater has a body formed of a fused head and thorax, known as a cephalothorax, and an abdomen. Its eight legs span some 28 cm (11 inches) and are bested in length only by those of the giant huntsman spider (Heteropoda maxima). The third and fourth pairs of legs have characteristic spines. The goliath birdeater is the heaviest known spider and can weigh up to 170 grams (6 ounces), about the same as a regulation pocket billiards (pool) ball. Its enormous body reaches up to 12 cm (5 inches) in length and is about the size of a human fist.

Like all tarantulas, goliath birdeaters are mygalomorphs (suborder Orthognatha) and thus have jaws that move forward and down (rather than sideways and together, which is characteristic of araneomorphs [suborder Labidognatha]). Goliath birdeaters have two pairs of appendages near the mouth that aid in feeding: chelicerae and pedipalps. The more central chelicerae contain the venomous fangs, which can be more than 3 cm (1 inch) long. The more lateral, leglike pedipalps are primarily used as feelers and to manipulate food and are also used by the male for reproduction.

Natural history

Goliath birdeaters are nocturnal hunters and live in silk-lined burrows under rocks and roots. Their natural camouflage allows them to blend in with fallen leaves and ambush their prey. Despite having eight eyes, they have poor vision and rely on their sensitive leg and abdomen hairs to pick up vibrations from nearby creatures.

The spider is an ambush predator and mostly feeds on earthworms, insects, frogs, and toads. However, it is opportunistic and will also kill and eat small mammals such as bats and rodents, as well as reptiles such as snakes and lizards. Small birds and bird eggs are also sometimes eaten. After injecting its prey with venom, the spider drags its meal into its burrow, where it spits digestive juices onto the dead animal to break down soft tissue. It consumes the liquified remains, leaving behind only fur and feathers, skin, and skeleton.

Generally solitary creatures, goliath birdeaters meet only to mate, and the male dies within several months thereafter. The gravid female spins a web into which she deposits 50–200 fertilized eggs. She then wraps them into a sac the size of a tennis ball, which she covers with some of her urticating bristles. A protective mother, she carries the egg sac until the spiderlings hatch. The young live in the mother’s burrow for several weeks until they are large enough to defend themselves, and stay close for up to three years. Like all spiders, goliath birdeaters molt to grow, casting off exoskeletons to make way for larger ones. In their first year, spiderlings molt five to six times. They reach sexual maturity in two to three years.

Female goliath birdeaters can live for 20 years, while males survive for 3–6 years.

Are you a student?

Get a special academic rate on Britannica Premium.

Subscribe

Defense and bite

To ward off predators such as coatis, the goliath birdeater may rear up on its hind legs to appear even larger and to flash its fangs. For defense, the furry arthropod uses the bristles covering its body in several ways. Through a form of stridulation, the goliath birdeater rubs hooked hairs on its legs together to produce a hissing noise that can be heard from almost 5 meters (15 feet) away. Additionally, it can unleash a cloud of urticating hairs by rubbing its hind legs against its abdomen, irritating the eyes, face, and respiratory passages of a large potential predator for days. The airborne harpoon-shaped hairs are capable of killing smaller creatures such as mice. The spiders are sometimes kept as pets, and most owners use gloves to avoid contact with the urticating bristles when handling.

To its relatively small prey, the spider’s neurotoxin is deadly. On humans, a bite from the goliath birdeater has been compared to a wasp’s sting—painful but nonlethal.

Formal discovery

The goliath birdeater was first scientifically documented by the French zoologist P. A. Latreille in his 1804 Histoire naturelle, générale et particulière des crustacés et des insectes. Latreille named the spider mygale de Leblond, or “Leblond’s tarantula,” in honor of French colonizer and naturalist Jean Baptiste Leblond, who first encountered the spider in Cayenne, French Guiana.

Its common name comes from an 18th-century engraving that depicts a different tarantula consuming a hummingbird. In fact, all members of the Theraphosa genus hold the moniker of “bird eaters.”