Underground Giants: The Gippsland Earthworm

Have you ever been digging around in some rich, damp soil and come across an earthworm? When we think of earthworms, we usually think of small, wriggly critters that can just barely fit in the palm of our hand. But there are many gigantic types of earthworms around the world that can grow to astonishing sizes, and one of them is the Giant Gippsland earthworm (Megascolides australis) – on average, these pinkish-grey earthworms reach one meter (three feet) in length (and weigh about the same as two large hamburger patties), but can be more than two or three meters long! They’re so big that when first discovered, in the 1870s, they were thought to be a species of snake. These earthworms only live in a small part of Australia. In fact, this area has become so reduced in size (due to human settlement) that these peaceful giants are classified as a threatened species and are being protected.

Although they don’t come to the surface (except during heavy rains), these giants can be detected by the “gurgling” noises they make when a person walks on the ground above them. (This is the earthworm trying to get away from the vibrations caused by the person’s feet.) These sounds are even more impressive knowing that these earthworms live relatively deep underground, at a depth of about 0.5 to 1.5 meters below the surface. Down there, the earthworms live in a moist, complex burrow system that is poorly understood. But we do know that they lay impressively large, transparent egg cocoons — each 4 to 8 centimeter (cm)-long one holds a single earthworm baby that takes a year to hatch, and it emerges 20 cm long! (Continue on to watch a video with amazing footage of one of these cocoons.)

The baby earthworm takes 5 years to reach its mature adult size, and can live for 10 years or more altogether. They mostly eat roots and other organic material that’s down in the soil, recycling its nutrients. And although they’re hermaphrodites, when they’re ready to mate they need to find another individual to fertilize eggs with.

These giants have been enduring hard times in their native region of Gippsland (in Victoria, Australia). They live in a particular type of clay soil with many sources of water nearby (which are important for keeping their burrows moist). The area used to be a eucalyptus forest, but with the arrival of European settlers, it was cleared for farming. The loss of vegetation, as well as disturbances brought with animal herds and farming practices, significantly diminishing their range. They’re now only found in an area of about 440 km² (or about 100,000 acres, or 170 miles²) that is mostly on private land. They’ve become a protected, threatened species, and there are concerns that they may become extinct.

Studying these critters has also proven quite difficult. Because they are relatively fragile, digging them up and handling them can be fatal for the worms, and breeding efforts in captivity have been futile (which has also been the case for other species of giant earthworms).

The Giant Gippsland earthworm is just one more example of the remarkable spectrum of biodiversity right here on Earth, and one more life-form that we need to be careful to take care of so it can just keep being its amazing self.

For further reading:

• Museum Victoria’s article “Giant Gippsland Earthworm”
• Australianfauna.com’s article “Giant Gippsland Earthworm”
• The Australian Government’s Department of the Environment’s article “Megascolides australis — Giant Gippsland Earthworm”
• BBC’s video Giant Gippsland Earthworm
• Роман Крушеницкий’s post Giant Earthworm Australia
• Teisha J. Rowland’s book Biology Bytes: Digestible Essays on Animals Both Commonplace and Bizarre