Do Goliath Birdeaters Really Eat Birds? What They Actually Eat

Where does the name “birdeater” come from?

In 1699, the German-born naturalist and artist Maria Sibylla Merian traveled to the Dutch colony of Suriname in South America to study insects and plants. Back in Amsterdam, she published Metamorphosis insectorum Surinamensium in 1705, a large book of 60 engravings. One plate shows a big, hairy spider dragging a hummingbird from its nest, with ants swarming over the same branch.

The picture made a huge impression in Europe. Large tarantulas became known as “bird-eating spiders”, and the word for tarantula in German, Vogelspinne, means “bird spider”. Some later writers doubted that spiders ever ate birds and treated Merian’s picture as fantasy.

The spider in the engraving was probably not a Goliath birdeater. It is shown on a tree branch, and many arachnologists think it was one of the smaller, tree-dwelling pinktoe tarantulas of the genus Avicularia, whose scientific name comes from the Latin for “little bird”. The Goliath birdeater (Theraphosa blondi) was scientifically described only in 1804 and lives in burrows on the ground. It inherited the bird-eating label because it is the largest of all the bird-eating spiders.

What do Goliath birdeaters actually eat?

Goliath birdeaters are opportunistic predators that eat almost any animal they can overpower. Observations in the wild show a diet dominated by invertebrates that live on and in the rainforest floor:

• Earthworms, which are large and abundant in the damp soils where the spiders live.
• Insects, including beetles, crickets, katydids and cockroaches.
• Other arthropods, such as millipedes, centipedes and other spiders.

Their size lets them take bigger prey too. Goliath birdeaters have been recorded eating frogs, toads, lizards, small snakes and small rodents. These vertebrates are an occasional bonus rather than a staple. Birds, despite the name, are among the rarest items of all. For a broader look at spider diets, see what do spiders eat?

How do Goliath birdeaters hunt?

Goliath birdeaters do not build webs to catch prey. They are sit-and-wait hunters that rest at or near the entrance of their burrow at night. Fine hairs on their legs and silk threads around the burrow mouth pick up the vibrations of an animal moving nearby. When prey comes close, the spider lunges, grabs it with its front legs and drives in its fangs.

The venom quickly subdues small animals. The spider then carries its catch into the burrow and pours digestive juices over it, which break down the soft tissues so that the spider can suck up the liquid. Large prey can take many hours to finish, and a big meal can keep a tarantula going for a long time.

Can a tarantula really catch a bird?

Yes, but the right circumstances are rare. A large tarantula is strong enough to kill a small bird, and its venom works on vertebrates. The problem is opportunity: a spider that hunts from a burrow on the forest floor at night rarely meets a bird. A fledgling that has fallen to the ground, a bird nesting low down, or one roosting within reach might occasionally be caught.

Merian’s picture was eventually backed up by observation. In The Naturalist on the River Amazons (1863), the English naturalist Henry Walter Bates described finding a large hairy spider beside a dense web on a tree trunk in the Amazon, with two small finches caught in the silk. One was dead, and the other lay beneath the spider. Bates remarked that Merian’s account had come to be widely doubted, and that local residents found the sight a novelty. Modern naturalists have also recorded tarantulas eating vertebrates now and then, such as a large tarantula in the Peruvian Amazon photographed eating a young opossum in a 2019 study, but birds remain a very small part of tarantula diets.

Do other spiders eat birds?

A few do, occasionally. The spiders most often involved are not tarantulas but large web-builders, especially the golden orb-weavers of the tropics, whose strong webs can be more than 1 m (3 ft) across. Small birds, sometimes hummingbirds, now and then become entangled, and some are eaten. Records of birds caught in spider webs come from many parts of the world, but each case is a rarity.

Hummingbirds feature in many of these stories because they are tiny and feed among flowers and foliage where webs are common. Ironically, hummingbirds themselves eat many spiders and collect spider silk to build their nests, as explained in what do hummingbirds eat?

Why the name stuck

“Birdeater” is a catchy name, and it fits the Goliath birdeater’s dramatic size: up to about 175 g (6.2 oz) in weight and about 30 cm (12 in) across the legs. It is the heaviest spider on Earth, as shown in our list of the largest spiders in the world. But a more accurate name might be “Goliath wormeater”. The spider’s reputation also makes it seem far more dangerous to people than it is; the real risks are covered in are tarantulas dangerous?