Moles are subterranean dwellers known for their remarkable ability to excavate extensive underground networks. These small mammals spend nearly their entire lives beneath the soil, constantly tunneling in search of food and creating intricate habitats. Their presence is often detected by the distinctive raised ridges and mounds that appear on the surface.
The Remarkable Speed of Mole Excavation
Moles are fast diggers, capable of excavating extensive tunnels quickly. In optimal conditions, such as loose, moist soil, a mole can dig new tunnels at a rate of 12 inches per minute. This translates to an excavation pace of approximately 12 to 18 feet of tunnel per hour. A mole can construct as much as 150 feet of new tunnels in a single day.
Their excavation speed is particularly evident in surface runways, which can extend at a rate of 100 feet (30 meters) per day. This rapid tunneling is necessary for survival, as moles constantly search for food. Their ability to quickly create and navigate these networks highlights their specialized adaptations for a life underground.
Anatomy and Techniques for Efficient Digging
Moles possess physical adaptations that enable rapid, powerful excavation. Their forelimbs are broadly shaped like shovels, equipped with large, blade-like claws to efficiently move soil. The bones of their shoulder girdle—including the clavicle, scapula, and humerus—are highly developed to withstand significant muscular strain during digging.
Muscles in their pectoral girdle are hypertrophied, allowing moles to generate substantial force for pushing soil. The “prepollex,” often called an “extra thumb,” provides additional support for their digging motion. Moles “swim” through the soil, compacting loose earth into the tunnel walls rather than pushing it to the surface. Their fur lacks a directional nap, allowing them to move backward or forward through tunnels with equal ease without trapping soil.
Understanding Mole Tunnel Systems and Their Purpose
Mole digging is driven by the need to find food and establish a secure habitat. Moles construct two main tunnel types: shallow surface runways and deeper permanent burrows. Surface runways are visible as raised ridges, primarily used for foraging earthworms, grubs, and other insects near the soil surface. These foraging tunnels can be temporary, sometimes abandoned after a single use.
Deep runways serve as main travel avenues, connecting feeding areas with nesting sites, and are located 3 to 12 inches below the surface. These deeper tunnels provide shelter from predators and environmental extremes, often containing nest cavities lined with vegetation, typically found 12 to 18 inches underground. Moles also dig to establish and defend territories, creating extensive networks spanning hundreds of feet. Soil conditions influence tunneling; moles prefer loose, moist soil and dig deeper during dry or cold periods to access food and maintain a stable environment.