A burrow is a hole or tunnel excavated into the ground by an animal, serving as a space for habitation or temporary refuge. These underground structures are a form of shelter, offering protection from predators and harsh environmental conditions like extreme temperatures or fires. Many animals also use burrows to store food and to safely raise their young. Burrows can be found across nearly every biome and are constructed by diverse animal species, ranging from tiny amphipods to large polar bears.
Common Visual Characteristics
Regardless of the animal that creates it, a burrow typically features several universal physical attributes. The most obvious characteristic is the entrance, which can vary in shape from round to oval or irregular, and in general diameter. Burrows also often involve the presence of excavated soil, which may form a distinct mound or a fan-shaped pile of dirt near the opening.
The area surrounding a burrow often shows signs of disturbance. These can include worn paths leading to the entrance or trampled vegetation, indicating regular animal activity.
How Burrow Appearance Varies by Animal
The appearance of a burrow can differ significantly depending on the animal that constructed it, reflecting their unique digging behaviors and needs. For instance, rabbit burrows, often called warrens, typically have multiple entrances, sometimes without accompanying dirt mounds. These holes are usually between 4 to 6 inches (10-15 cm) in diameter and lead to complex networks of tunnels that can extend up to 10 feet deep and 150 feet long, providing safety and space for colonies.
Badger burrows, known as setts, are larger and more elaborate. They feature distinct D-shaped entrances, wider than they are tall, typically measuring around 12 inches (30 cm) wide by 10 inches (25 cm) high. Setts often have a large spoil heap of excavated soil, rocks, and even old bedding material at the entrance. A single sett can comprise up to 1,000 feet (300 meters) of tunnels and as many as 40 openings, reflecting their use by multiple badgers.
Groundhog burrows usually have one main entrance with a noticeable crescent-shaped mound of excavated soil. This primary opening is typically 10 to 12 inches (25-30 cm) in diameter. Groundhog burrows can extend 15 to 25 feet (4.5-7.6 meters) horizontally and include chambers for nesting, sleeping, and waste. They may also have one to four less obvious auxiliary or “escape” exits.
Snakes generally do not dig their own burrows but instead utilize existing holes created by other animals like rodents or turtles. Their preferred holes are typically small and narrow, ranging from about 0.5 to 4 inches (1.2-10 cm) in diameter, reflecting their slender body shape. These entrances often appear clean, lacking the fresh soil or debris common around actively dug burrows, and may be camouflaged by natural elements.
Small rodents, such as mice and voles, create much smaller, often inconspicuous burrows. Mouse holes might be about 1.2 inches (3 cm) in diameter, sometimes camouflaged with debris like small stones or twigs. Vole holes are typically 1 to 2 inches (2.5-5 cm) in diameter and are often accompanied by shallow surface runways through vegetation. These burrows can be relatively simple, sometimes just a linear tunnel leading to a nest.
Insects also create burrows, which are generally very small and can be quite intricate. Some insects, like digger bees or sand wasps, excavate tunnels for nesting. Social insects, such as ants or termites, build extensive underground tunnel systems for their colonies. These insect burrows vary greatly in size and complexity, ranging from simple holes to elaborate networks with specific chambers for different purposes.
Indications of an Active Burrow
Observing certain signs around a burrow can help determine if it is currently in use. Fresh tracks and footprints near the entrance are strong indicators of recent animal activity. The presence of fresh droppings or feces near the burrow opening also suggests an animal is regularly using the space.
Recent excavation marks, such as freshly dug soil around the entrance, point to ongoing digging. A well-maintained entrance, clear of debris like cobwebs or leaves, often signifies an active burrow. Conversely, inactive burrows might be blocked by leaves, sticks, or soil. The presence of fresh food remains or gnawed vegetation nearby can also indicate an active resident.