Identifying Subterranean Dwellers
Animals that live underground are broadly categorized by their adaptations for a subterranean existence. The scientific term for animals primarily adapted to digging and living underground is “fossorial.” This term originates from the Latin word “fossor,” meaning ‘digger.’ Fossorial animals spend a significant portion of their lives creating and inhabiting burrows beneath the Earth’s surface.
Some fossorial animals, such as rodents, may emerge above ground for various activities, while others, known as subterranean fauna, live almost exclusively underground. Earthworms, for example, are considered subterranean animals, spending their entire lives beneath the soil.
Adaptations for Underground Life
Living underground presents challenges, leading to specialized physical and behavioral adaptations in fossorial animals. Many burrowing mammals exhibit spindle-shaped or cylindrical bodies that taper at both ends, helping them navigate dense subsurface environments. Their limbs are often short and stout, with broad, strong forelimbs and long claws for loosening soil, while hind limbs disperse excavated material. Some species, like moles, have forelimbs that rotate outward, allowing a swimming-like motion when digging.
Sensory adaptations are prominent in these animals. With limited light underground, many fossorial creatures have reduced or absent external ears and small or hidden eyes. Instead, they rely on enhanced senses of touch, smell, and hearing. Moles, for instance, possess highly sensitive snouts with microscopic tactile structures to detect their environment and prey. Some underground animals, like the Cape mole rat, communicate through seismic vibrations by “drumming” on burrow walls, as sound travels efficiently through solid earth.
Behaviorally, living underground offers several benefits, including protection from predators, stable temperatures, and access to food or water. Burrows provide refuge from extreme heat or cold and can serve as safe nurseries for young. Some social species, like naked mole-rats, cooperatively construct extensive tunnel systems with multiple chambers for living and foraging. This teamwork reduces energy and time spent vulnerable during burrow construction.
Diverse Examples
Diverse animals have evolved fossorial lifestyles across various groups. Among mammals, moles are well-known for their extensive burrowing, with species like the eastern mole capable of digging over 45 meters of tunnels in a single night. Badgers are also proficient diggers, creating complex burrows called “setts” that can be used for generations. American badgers are particularly adept at digging to hunt burrowing rodents.
Reptiles also include fossorial species, such as blind snakes, small, non-venomous snakes with degenerate eyes that live primarily underground or in leaf litter. Their smooth, shiny scales protect them from insect bites as they forage for ants and termites. Caecilians, limbless amphibians resembling large worms or snakes, spend most of their lives burrowing in moist tropical soils. Their hard, pointed skulls allow them to push through dirt, and they have tiny or hidden eyes.
Insects, too, exhibit fossorial behaviors. Mole crickets, for example, are cylindrical-bodied insects with shovel-like forelimbs adapted for digging and creating tunnels. They spend most of their lives underground, often damaging plant roots as they tunnel and feed.