Why Study Caves?


Cave ecosystems are perhaps the most fragile ecosystems on Earth.  This is due to the hypersensitivity of most cave-roosting bats and other cave-dwelling critters to human disturbance.  Female bats will often use caves to raise their pups.  These roosts are called maternity or nursery colonies.  In temperate climates, where bats hibernate, they may use certain caves as “hibernaculums.”  Both maternity/nursery roosts and hibernaculums are often very sensitive to human disturbance.  Even activities believed to be harmless, such as shining a light into a bat colony may cause some species to abandon their roost and even their pups. 

Also, cave adapted and limited organisms (troglobites and stygobites) are often the most sensitive.  These animals may be endemic (they occur in one cave or region and no where else in the world), have low population numbers and often take a long time to reproduce.  Disturbance including human visitation, as well as surface impacts such as pollution and deforestation can dramatically alter the subterranean world.  Sometimes these impacts can result in causing great damage to these organisms.  As a result, many of these species may be endangered with extinction.  

Despite the sensitivity of most cave-dwelling animals, these ecosystems remain poorly understood.  We know very little about how the community, structure and function of these systems.  For example, for a cave, how many animals live in the cave?  How do they interact?  Who eats whom?  What is each animal’s job within the ecosystem?  How are certain cave-dwelling animals distributed on the landscape?  How sensitive are these communities to disturbance (human visitation, surface pollution, natural surface environment conversion)? 

How extreme are cave extremophiles?  What are the threshold conditions under which they occur?  How will these ecosystems be affected by global climate change? 

All of these questions are very interesting to a cave scientist, because only a small fraction of caves in any region of the world has been studied at an ecological system level.  This means others and I have a lot of work to do.  There are thousands of unexplored caves throughout the world that needs our help.  We must first characterize the ecological communities of caves, and then we may begin to ask some of these fascinating questions.  For now, I want to focus my efforts on caves in the southwestern United States, Belize, Chile, and perhaps even Saudi Arabia. 

So, what types of animals use caves?

Caves are nutrient starved environments.  Most cave ecosystems rely on inputs from the surface to support life underground.  Nutrient inputs include dead vegetation brought into the cave from flooding, and by bats and crickets in the form of guano, and to a lesser extent wind-blown vegetation or nutrients percolating through the cap stone into the cave environment.  In a rare cases, life in cave ecosystems are supported by chemoautotrophic microbes (organisms that literally eat the minerals in the rock).  These microbes often serve as the center of the food web and can support entire invertebrate communities.

Animals occurring in these nutrient starved ecosystems have strange names such as “troglobite,” “stygobite,” “trogloxene” and “troglophile.”  Troglobites and stygobites are cave-adapted (troglomorphic) animals.  These critters are restricted to life in a cave.  They often lack skin pigmentation and eyes and have elongated appendages that help them move more efficiently through the cave environment.  Troglobites are terrestrial cave-adapted species that occur only in caves or similar subterranean habitats.  Examples of animals that have become troglobitic include spiders, beetles and millipedes.  Stygobites are the aquatic version of a troglobite, which include eyeless, shrimp, and crawfish.  Trogloxenes are animals that require the cave environment (or similar subterranean environment) during some part of its life cycle.  They use the cave for shelter, but return to the surface (epigean habitats) to forage.  Some trogloxenic are bats and cave crickets.  Troglophiles are animals that can use either the cave or surface environment.  They simply do not care.  Some examples of troglophiles include snakes, salamanders, frogs, and rodents.  Microbes are the smallest organisms that occur in caves.  Called “bugs” by the scientists who study them, these microbes are some of the most extreme organisms living in caves.  These extremophiles live off the minerals on rock, minerals within subterranean pools, and in some cases filter nutrients from the air within the cave.