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Word of the Week: Fossorial

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Welcome to Word of the Week! Stay tuned for a new word each Wednesday to amp up your nature vocabulary!

What Does Fossorial Mean? 

Fossorial [fo-SOHR-ee-uhl] (adjective): An animal adapted to living underground, often by digging a burrow and/or tunnels. Some examples of fossorial animals are earthworms, ants, moles, voles, and shrews.

What are Fossorial Organisms? 

Fossorial or semi-fossorial animals are organisms that have adapted successfully to the lifestyle of living underground by digging burrows and tunnels. Some animals such as rodents will live in burrows for most of the day but will resurface for various times throughout the day. However, there are other species that live exclusively underground, called subterranean fauna.

There are many species of animals from mammals to invertebrates that evolved over time and gained certain characteristics to help them adapt to the fossorial lifestyle. For example in mammals, there are six major external features that are the following:

  • Fossorial mammals will have a fusiform, spindle-shaped body
  • Lesser developed or missing eyesight as there is little light or no light in subsurface
  • Small or no external ears to help reduce any natural friction when burrowing
  • Short or stout limbs as strength are more important than speed
  • Short or missing tail
  • Broad and stout forelimbs including long claws to help loosen anything while burrowing underground while the hind legs will be used for stability.


Other creatures adapted to live underground to help with temperature regulation, create homes, protect themselves from predators, or to keep food safe. The star-nosed mole, for example, has an impressive and ultra sensitive nose to make navigating the underground world far easier.

In the animal kingdom there are many animals that have adapted to living underground that might surprise you!


Yes that’s right! Bats are considered fossorial animals. Though bats don’t dig underground, they do live underground spaces such as caves, in cracks and crevices in rocks and trees. Bats navigate with the help of bio sonar and echolocation.


Moles are considered one of the best diggers, and are experts at opening long tunnels below the earth. In general you can identify a mole by their small eyes compared to their body. Makes sense that they don’t need strong vision to live at ease in the dark. They have a stocky body, dense fur, and extra thumbs. Moles will feed on fossorial invertebrates such as earthworms, snails, and larvae.

Pink Fairy Armadillo 

The pink fairy armadillo is among the most rare animals. They are about 7cm to 10cm long, meaning they can fit in your hands!

Though they are small, these animals are strong and are protected by a dorsal shell. The pink fairy armadillo are nocturnal solidarity animals that will spend most of their time digging.


A slug is any terrestrial gastropod mollusc without a shell. While there many different orders and families of slugs, they share some common features such as the shape of their body, their consistency, and their grayish brown colour.

Slugs will only come out at night and for a short period of time. When the season is dry they will stay underground for almost 24 hours waiting for rain. These creatures are related to snails and are considered invertebrates.

Camel Spider

Camel spiders are also known as wind scorpions or sun spiders. They get their most common name from the long legs that look very similar to camel legs. These spiders can measure up to 15 cm in length and they are very good runners. They can become aggressive however, their venom is not fatal but the sting can be unpleasant. These creatures will spend their time under rocks, and holes in dry habitats such as the desert.


Finally we have the scorpion. These animals can inhabit and bury themselves in the most extreme ecosystems — from frozen ground to thick grass. They will spend the warmest hours of the day underground and will hunt at night. Scorpions are photophobic, meaning they will hide from light.

During early spring in High Park, semi-fossorial mammals such as chipmunks and groundhogs or woodchucks, come out to forage and warm up in the sun.

Another very common fossorial animal here in High Park is the ant! There are over 200,000 species of ant that come under the Formicidae family and they are experts in underground architecture. They are so good that digging complex colonies is easy for them! Ants are considering arthropods, so they are not vertebrates.

Fossorial animals have the potential to impact their entire ecosystem. Vacant burrows are often reused and adopted by other species, or passed down through the generations. For example, old woodchuck burrows can become homes for rabbits, foxes, skunks, or weasels. Burrows and tunnels also create air pockets and pathways for water and nutrients to move which can improve soil quality.

Just as humans are part of nature, so are our fossorial animals friends! Next time when you walk around your neighborhood or through a trail in High Park keep a close eye out for these fossorial animals. Bring your friends and family along, as you never know, you might find some ant colonies and the homes of earthworms!

To learn more about different animals, their habitats and more come join our programs such as our guided tours or to those that like to read books have a look at our Nature Book Club. If you want to get involved, help us out by volunteering with us!

Sammy Tangir – Sammy is a serious nature nerd and especially enthusiastic about plants! When she is not thinking of next week’s nature word, she is working as an outdoor educator and practicing her wood carving skills.