Burrow
A burrow is a hole or tunnel excavated into the ground by an animal to construct a space suitable for habitation or temporary refuge, or as a byproduct of locomotion. Burrows provide a form of shelter against predation and exposure to the elements, and can be found in nearly every biome and among various biological interactions. Many animal species are known to form burrows. These species range from small amphipods,[1] to very large vertebrate species such as the polar bear.[2] Burrows can be constructed into a wide variety of substrates and can range in complexity from a simple tube a few centimeters long to a complex network of interconnecting tunnels and chambers hundreds or thousands of meters in total length; an example of the latter level of complexity, a well-developed burrow, would be a rabbit warren.
For other uses, see Burrow (disambiguation).Invertebrate burrows[edit]
Scabies mites construct their burrows in the skin of the infested animal or human. Termites and some wasps construct burrows in the soil and wood. Ants construct burrows in the soil. Some sea urchins and clams can burrow into rock.
The burrows produced by invertebrate animals can be filled actively or passively. Dwelling burrows which remain open during the occupation by an organism are filled passively, by gravity rather than by the organism. Actively filled burrows, on the other hand, are filled with material by the burrowing organism itself.[15]
The establishment of an invertebrate burrow often involves the soaking of surrounding sediment in mucus to prevent collapse and to seal off water flow.[15]
Examples of burrowing invertebrates are insects, spiders, sea urchins, crustaceans, clams and worms.
Excavators, modifiers, and occupants[edit]
Burrowing animals can be divided into three categories: primary excavators, secondary modifiers and simple occupants.[16] Primary excavators are the animals that originally dig and construct the burrow, and are generally very strong.[17] Some animals considered to be primary excavators are the prairie dog, aardvark and wombat.[18] Pygmy gerbils are an example of secondary modifiers, as they do not build an original burrow, but will live inside a burrow made by other animals and improve or change some aspects of the burrow for their own purpose.[17] The third category, simple occupants, neither build nor modify the burrow but simply live inside or use it for their own purpose.[17] Some species of bird make use of burrows built by tortoises, which is an example of simple occupancy.[17] These animals can also be referred to as commensals.[17]
Fossil burrows[edit]
Burrows are also commonly preserved in the fossil record as burrow fossils, a type of trace fossil.