Animals burrow for a variety of reasons, such as nesting, hibernation, food supply and warmth. Some animals even take advantage of burrows that other animals have made without having to do the digging themselves. Others only use their burrows as an opportunity to ambush unsuspecting prey. Burrowing animals are represented in all of the classes of the animal kingdom.
Many mammals live in burrows. Some of the most common burrowing animals found in North America include various types of mice, moles, prairie dogs, badgers and ground squirrels. Burrows not only serve as a home for these creatures, but also benefit the environment by aerating the soil. These creatures also fertilize the soil by leaving their droppings and nesting materials below ground, and encourage plant growth by depositing seeds throughout their underground tunnels. Since many of these animals are prey animals, these burrows offer some measure of protection from non-burrowing predators.
Reptiles are ectothermic, or cold-blooded. Because of this, they rely on their environment to provide the heat necessary to maintain body functions such as digestion, circulation, respiration and reproduction. The temperature underground is much more consistent than on the surface, making burrowing reptiles quite common. Many snakes and lizards spend considerable time underground, either to keep warm or to avoid being eaten. Turtles do not live underground, but do lay their eggs in buried nests; unfortunately this doesn’t always deter predators from finding and eating their eggs.
Amphibians require moisture so that their smooth, scaleless skin does not dry out. Moisture levels are higher under the surface of the ground; for this reason, most amphibians spend much of their time under rocks or logs, or in shallow burrows. Frogs, toads and salamanders maintain optimal moisture levels by staying nestled in moist earth.
Fish use their fins to kick up sand from the ocean floor and cover themselves. This provides valuable camouflage, allowing them to remain invisible to predators. It also makes them invisible to their prey. When an unsuspecting fish swims past, these fish pop up from under the sand and scoop them up in their mouths. Some fish that use this natural cover are the flounder, gobie, angel shark and various types of rays.
While birds are typically associated with trees and flight, there are some birds that build their nests and rear their young underground, or in burrows dug into cliff walls. Some of these birds include kingfishers, European rollers, ground woodpeckers and the burrowing owls.