How Big Is a Goliath Bird Eating Tarantula? Up to 11 Inches

The Goliath birdeater tarantula (Theraphosa blondi) is not a bird, despite its misleading name, and it does not eat birds regularly. This massive spider is one of the largest in the world by mass and size, with a leg span reaching up to 11 inches (28 centimeters) and weighing as much as 6 ounces (170 grams). Often mistaken due to its name, the so-called 'Goliath bird eating tarantula' may occasionally consume small birds, but this behavior is rare and not a primary part of its diet. Instead, it primarily feeds on insects, amphibians, reptiles, and small mammals. Understanding how big a Goliath birdeater tarantula truly is requires examining both its physical dimensions and its ecological role in South American rainforests.

Understanding the Name: Why Is It Called a Bird-Eating Tarantula?

The name Goliath birdeater conjures dramatic images of a giant spider snatching birds from low-hanging branches. However, this moniker is more myth than reality. The species was first described in the 1700s by European naturalists who observed a specimen consuming a hummingbird, leading to the sensational name that persists today. In truth, such events are extremely uncommon. The term 'how big is a Goliath bird eating tarantula' often leads people to imagine a predator specialized for avian prey, but biology tells a different story. The name reflects historical observation bias rather than dietary preference.

Despite its name, the Goliath birdeater's diet consists mainly of invertebrates like crickets and beetles, along with worms, frogs, lizards, and even small rodents. While it has the strength and venom to subdue a young or injured bird, doing so is energetically inefficient compared to easier prey. Therefore, while technically capable of eating birds, the Goliath birdeater rarely does so in the wild. The misnomer continues to capture public imagination, making it one of the most famous—and feared—spiders on Earth.

Physical Characteristics: How Big Is a Goliath Bird Eating Tarantula?

To answer the question 'how big is a Goliath bird eating tarantula,' we must look at several key measurements. The Theraphosa blondi holds the title of the world’s largest tarantula by mass and overall size. Its body length averages between 4 to 5 inches (10–13 cm), while its leg span—the distance from the tip of one front leg to the tip of the opposite rear leg—can reach up to 11 inches (28 cm). For perspective, that’s nearly the size of a dinner plate.

These spiders are heavily built, with robust exoskeletons and powerful chelicerae (fangs) used for crushing prey. Their weight can range from 4 to 6 ounces (120–170 grams), making them significantly heavier than most other tarantula species. Females tend to be larger and live longer than males, surviving up to 15–25 years in captivity, whereas males typically live only 3–6 years after reaching maturity.

Coloration varies slightly among individuals but generally includes shades of tan, brown, or gray with fine reddish-brown hairs covering the body. These urticating hairs serve as a defense mechanism; when threatened, the spider can kick them off into the air, causing irritation to predators’ skin, eyes, or respiratory systems.

Habitat and Geographic Range

The Goliath birdeater is native to the rainforests of northern South America, particularly in countries such as Venezuela, Guyana, Suriname, French Guiana, and parts of northern Brazil and eastern Colombia. It thrives in humid, tropical environments with dense vegetation and soft, moist soil—ideal conditions for burrowing.

Unlike arboreal tarantulas, the Goliath birdeater is terrestrial and fossorial, meaning it spends much of its time underground in self-dug burrows. These shelters protect it from extreme weather and predators while maintaining high humidity levels essential for survival. Burrows can extend several inches deep and are often lined with silk to stabilize the walls and retain moisture.

Due to habitat destruction and collection for the pet trade, populations in some regions are under pressure. However, the International Union for Conservation of Nature (IUCN) currently lists the species as Least Concern, though localized declines have been noted. Deforestation for agriculture and mining poses the greatest threat to long-term survival in the wild.

Diet and Feeding Behavior

While the idea of a 'bird-eating' tarantula sounds fearsome, the reality is far less dramatic. The Goliath birdeater is an opportunistic carnivore. Its primary food sources include large insects, earthworms, amphibians like tree frogs, small snakes, and occasionally nestling mammals such as mice.

When hunting, the spider relies on vibration detection through its legs and specialized sensory organs. It ambushes prey near its burrow entrance, using speed and powerful fangs to inject venom and digestive enzymes. The resulting slurry is then sucked up as a liquid meal. Despite possessing venom, the toxin is relatively mild to humans—comparable to a bee sting—but can cause pain, swelling, and discomfort.

Bird predation, while possible, is rare and usually involves weak, injured, or very young birds unable to escape. Documented cases are limited and mostly anecdotal. Thus, the notion that this spider regularly eats birds is a misconception rooted more in folklore than fact. A more accurate description would be 'occasionally bird-consuming' rather than 'bird-eating.'

Lifecycle and Reproduction

The lifecycle of the Goliath birdeater begins with egg sacs containing hundreds of spiderlings. After mating—a risky endeavor for males, who may be cannibalized by females—the female produces a silken cocoon holding 100 to 400 eggs. She guards this fiercely for several weeks until the spiderlings emerge.

Spiderlings are tiny, measuring just a few millimeters across, but grow rapidly with regular feeding. They undergo multiple molts during development, shedding their exoskeletons to accommodate growth. Each molt carries risk, especially in adulthood, where failure to properly shed can lead to injury or death.

Females mature slowly, taking 3 to 6 years to reach sexual maturity, while males develop faster but die shortly after mating. Males often travel in search of mates, increasing their exposure to predators. Once mated, their biological purpose fulfilled, they seldom survive beyond a few months.

Human Interaction and the Pet Trade

In recent decades, the Goliath birdeater has gained popularity in the exotic pet trade due to its impressive size and striking appearance. However, keeping one requires significant expertise, space, and commitment. Enclosures must mimic natural conditions: spacious, humid, and equipped with deep substrate for burrowing.

Despite their intimidating presence, these spiders are generally docile unless provoked. Still, their size, defensive behaviors (including hissing and hair-kicking), and potential to inflict painful bites make them unsuitable for novice keepers. Additionally, importing live specimens is restricted or banned in many countries due to conservation concerns and invasive species risks.

Ethical considerations also arise regarding wild-caught versus captive-bred individuals. Wild collection contributes to population decline and ecosystem disruption. Responsible hobbyists are encouraged to source only from reputable breeders who practice sustainable methods.

Common Misconceptions About the Goliath Birdeater

Several myths surround this species, fueled by sensational media portrayals. One widespread belief is that the Goliath birdeater is highly dangerous to humans. In reality, no human deaths have ever been attributed to its bite. While the bite is painful, medical complications are rare.

Another myth is that these spiders actively hunt birds. As previously explained, bird predation is exceptional, not routine. Similarly, some believe they are aggressive toward humans, but they are typically shy and reclusive, retreating into burrows when disturbed.

Finally, many assume all large tarantulas are Goliath birdeaters. In fact, there are three recognized species within the Theraphosa genus: T. blondi, T. apophysis, and T. stirmi. All are large, but only T. blondi holds the official record for maximum size.

Scientific Research and Ecological Importance

The Goliath birdeater plays a vital role in its ecosystem as both predator and prey. By controlling populations of insects and small vertebrates, it helps maintain ecological balance. Its burrows also contribute to soil aeration and provide shelter for other organisms.

Scientists study the species to understand arachnid physiology, venom composition, and evolutionary adaptations. Research into its silk properties could inform biomaterial development, while studies of its sensory systems offer insights into non-visual navigation in dark environments.

Conservation biologists emphasize the need for habitat protection and monitoring of illegal wildlife trafficking. Public education campaigns aim to replace fear with understanding, highlighting the spider’s ecological value and dispelling exaggerated threats.

Characteristic	Measurement
Body Length	4–5 inches (10–13 cm)
Leg Span	Up to 11 inches (28 cm)
Weight	4–6 oz (120–170 g)
Lifespan (Female)	15–25 years
Lifespan (Male)	3–6 years post-maturity
Habitat	Tropical rainforests of northern South America
Diet	Insects, worms, frogs, lizards, small mammals; rarely birds

Frequently Asked Questions

• Can a Goliath birdeater kill a human? No, its venom is not lethal to healthy adults. Bites are painful but medically insignificant in most cases.
• Does the Goliath birdeater really eat birds? Rarely. Though capable, it primarily consumes insects and small animals. Bird predation is infrequent and opportunistic.
• How fast can a Goliath birdeater move? Despite its size, it can move quickly over short distances, especially when threatened or capturing prey.
• Is it legal to own a Goliath birdeater as a pet? Laws vary by country and state. Some regions require permits or ban ownership entirely due to safety and conservation concerns.
• What should I do if I encounter one in the wild? Observe from a distance and avoid disturbing it. These spiders are not aggressive and will retreat if left alone.