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Life survives in caves by adapting to the unusual habitat. Because sunlight does not penetrate beyond the twilight zone of a cave, the area just inside the entrance, plants that must capture energy from sunlight cannot grow. Therefore, the cave ecosystem is based on nutrients entering the cave via water and outside organisms venturing into the cave and depositing guano, eggs, debris, or their carcasses. These nutrients are in turn used by the organisms that spend their entire life cycles in the cave environment.
Bacteria in Caves
Bacteria lives in moist areas of caves, feeding on organic material that has seeped with the water through the "solid" rock. Some limestone caves have bacterial colonies that are chemoautotrophic, or "rock eating". These bacteria can derive all their necessary food and energy from rocks, minerals, or dissolved chemicals. They can form an ecosystem that is totally independent of the life-giving light from the sun. Research would be needed to determine if Lehman Caves is home to bacteria of this type.
Trogloxenes and Troglobites
Animals who use caves fall into several different categories. A trogloxene is a species who uses caves, but does not spend its entire life cycle within one. Examples are chipmunks, mice, and pack rats. These animals are dependent on vegetation for food and must leave regularly to forage. Bats feed on flying insects, such as mosquitos, and so must also must leave the cave to find adequate food.
The nesting material brought into the cave and droppings left behind by these temporary residents is a major source of nourishment for another type of animal known as a troglobite.
Troglobites are species that spend their entire life cycles in caves and include cave crickets, spiders, psuedoscorpions and the smaller mites and springtails. Often troglobites have adapted to the cave environment through morphological changes such as the loss of eyes and pigment and lengthening of appendages, as is seen in the cave dipluran. Though adapted to survive in the unique cave environment, they are dependent on organic material packed in by other animals or washed in from the surface. They often must optimize meals that are few and far between.
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Navigating in the Dark
Animals in the cave use a variety of senses to find needed shelter and food. Bats navigate through the pitch dark cave using echolocation, emitting sounds waves and listening to the echo in order to locate objects. Pack rats follow the scent of their urine trail to return to their nests, called middens. They will fill these nests with pine cones, aluminum can tops, or anything else interesting, even though they can not see the decorations in the darkness. Touch is also very important. Pseudoscorpions use their elongated pinchers to feel the route in front of them.
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Psuedoscorpion, approximately one inch long.
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Human Impacts
Cave life typically deals with very slow changing conditions (constant temperature and near constant humidity), constant darkness, and uncertain food supply. Humans have unintentionally changed the ecology of Lehman Caves, particularly, by introducing more food sources (wooden steps, lint, etc.), opening two new entrances, and installing electric lights. The lights, entrances, and tour groups slightly affect the temperature of the cave. Light in the previously dark cave allows plants to grow. These plants, mostly algae, are a source of food for animals. This can change what species live in the cave and how they interact.
Park rangers are trying to reduce these effects on the cave by turning out lights when tours are not in the cave and by not allowing visitors to bring food or beverages on tours.
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