A burrow animal excavates a hole or tunnel in the ground, creating a space for habitation, temporary refuge, or as a byproduct of movement. These underground structures, known as burrows, can range from simple, short tubes to complex networks of interconnected tunnels and chambers. Animals across nearly every biome engage in this behavior, adapting their dwellings to various substrates like soil, sand, or even rock. This fundamental survival strategy provides a secure environment beneath the surface.
Physical Adaptations for Burrowing
Burrowing animals possess specific physical characteristics that enable their subterranean lifestyle. Many have a fusiform, or spindle-shaped, body that tapers at both ends, which helps them move efficiently through dense underground environments. Powerful, short limbs and broad forelimbs with long claws are common, designed to loosen and displace soil.
Reduced or absent external ears and small or underdeveloped eyes are typical adaptations, as sight is less useful in dark underground conditions. For instance, moles have tiny eyes hidden under their fur and lack external ears, relying instead on their sense of touch. Specialized teeth, such as the continuously growing incisors of rodents, can also be used for digging. The skeletal structure of burrowers often includes a triangularly shaped skull and strong sternum, supporting the powerful musculature needed for excavation.
Survival Benefits of Burrows
Burrows offer numerous advantages for animals, significantly enhancing their survival. Protection from predators is a primary benefit, as the underground environment provides a secure refuge from threats above ground. Many burrows are designed with multiple entrances, allowing quick escape when danger approaches.
Underground burrows provide stable microclimates, offering insulation from extreme temperatures. Animals can escape intense heat in deserts or harsh cold in winter by retreating into their burrows, where temperatures remain more consistent.
Burrows also serve as safe places to raise young, protecting vulnerable offspring from predators and adverse weather. Many species use these underground nurseries for birthing and rearing their progeny until they are old enough to survive independently. Some social animals, like prairie dogs, even cooperate in constructing and guarding these communal nurseries. Additionally, some animals utilize their burrows for food storage, creating underground pantries to stockpile provisions for times of scarcity. Chipmunks, for example, store seeds and berries in their burrows for winter use.
Diverse Examples of Burrowing Animals
Burrowing behavior is widespread across the animal kingdom, found in various taxonomic groups. Mammals are well-known burrowers, including rabbits, whose complex burrows are called warrens, and badgers, which create extensive sett systems. Prairie dogs construct elaborate underground “towns” with multiple chambers and entrances. Moles and gophers are specialized diggers, with moles creating intricate tunnel networks and gophers building systems that can aerate soil. Even larger mammals like polar bears create maternity dens in snow or earth, and platypuses dig waterside burrows for nesting.
Reptiles also include burrowing species, such as some snakes and tortoises that dig their own holes. Among amphibians, various frogs, like the Mexican burrowing toad and Australian burrowing frogs, use muscular limbs to dig into the ground, often remaining hidden for long periods. Caecilians, legless amphibians, spend most of their lives in underground tunnel networks.
Insects exhibit diverse burrowing behaviors; ants and termites build extensive underground colonies, while some beetles, cicadas, and certain bees and wasps excavate burrows for nesting or feeding. Many invertebrates, such as earthworms, crabs, sea urchins, and even some spiders like funnel-web spiders, also create burrows for shelter or hunting.