When you think of cave animals, you may think of bats, but cave life is much more diversified. There are several hundreds of animal forms which are craving for caves. A cave is a natural opening in the ground extending beyond the zone of light and large enough to permit the entry of man. They are several types; no two caves are ever exactly the same. The major difference of the caves is their type. A cave can be a limestone cave, glacier cave, ice cave, mud cave, talus cave, sea cave, sandstone cave, or a lava cave. All these different types of caves hold special qualities that make them unique. Each was made in its own space over millions of years.
Zone to zone
Biology of a cave varies according to its zonation. The zone which lies right next to the opening is called ‘Entrance zone’, where sunlight penetrates and temperature variations can be observed. The zone next to it is called ‘twilight zone’, which characterized by very less light and much constant temperatures. Cave ends in ‘dark zone’, where there is no light and temperature is steady without any fluctuations. Caves are home to many animals. A troglobiont (‘troglo’ means cave or hole in Greek and ‘bio’ means life) is an organism that lives in a cave.
Depending on this zonation and the interaction among both, cave dwelling fauna also divided into groups. There are animals that live mainly on the Earth’s surface. But accidentlly they fall or are washed into caves accidentally. Some examples are turtles, surface fish and snakes. They are called ‘Accidentals’. These animals cannot live out their lives in caves because they are adapted to life on the Earth’s surface. Accidentals are usually only found in the entrance zone of caves.
Many animals use cave entrances as shelters for sleeping, hibernation, safety and reproduction, but are not fulltime cave dwellers. These animals which return to the earth’s surface in search of food can be referred to as ‘Trogloxenes’. Bats, mice, bears, raccoons, some cats, frogs, some salamanders and some insects like crickets are examples of trogloxenes. ‘Troglophiles’ are the ones that can live out their entire lives in caves.
They seem to be equally adapted for living and finding food inside or outside of the cave. They may be partly cave adapted, but not so much that they would find life outside, under proper conditions, unbearable. Some types of bats, swifts, cave crickets, pack rats, and some cave salamanders are examples of troglophiles. Troglobites are animals that have fully adapted to the cave environment and live their entire lives in caves. Some examples are cave crickets, cave spiders, blind Texas salamander, blind flatworms, eyeless shrimp, eyeless fish, cave beetles, cave crayfish, and some bristletails, isopods and copepods.
‘Dark world’ adaptations
Troglobites are often spending their lives in the ‘dark zones’ of the caves. They cannot live on the surface because of these adaptations. They have evolved with physical adaptations to cave life such as reduced or no vision, loss of colour pigments and elongated appendages. Some adaptations may be seen in troglobite insects, such as the extra-long antennas on the cave crickets, a plus when hunting for food in the dark.
Though bats are not blind, they use the mechanism called ‘echolocation’ to find their way through dark caves. They emit high-pitched sonar sounds, which reflect off of walls or other objects and allow them to sense their way. Echolocation also helps them find their insect prey. All These adaptations most likely evolved over several million years for them to suit in to a cave dwelling livestyle.