People usually visit caves for the adventure of a new
subterranean world or to see beautiful cave formations. But, below
the feet and over the heads of visitors to caves are surprising and
varied animals that make caves their home. Biologists divide
cave-dwelling animals into three groups: Troglobites, which are
restricted to caves; Troglophiles, who live in caves and on the
surface; and Trogloxenes, who regularly visit caves but can not
complete their life cycles in subterranean environments.
Troglobites are often very specialized animals adapted to live in
just one cave or a group of caves. Their adaptations may include no
eyes or pigment, elongated appendages and enhanced tactile senses.
These animals are very sensitive to change and disturbance.
Troglobites or their food supply, can be trampled by caver visitors.
Water pollution and surface developments may also poison cave
environments. Bats are Trogloxenes, but they too are very sensitive
to disturbance. They evolved to live in caves in complete darkness
and silence. Unwitting cave visitors bring lights and make noises
terrifying colonies of bats. Today a significant percentage of
animals on the Endangered Species list is cave dwelling bats and
invertebrates.
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| Calcina cloughensis is endemic to Clough Cave- it occurs exclusively in this cave and nowhere else in the world.
© NPS photo by Joel Despain. |
The unique cave animals of Sequoia and Kings Canyon are better
protected than most because they are lucky enough to make their home
in a National Park. This is important because the Sierra Nevada has
recently been identified as one of the five "hotspots" for
cave animal diversity in the United States. Some of the unique
animals of these mountains live in the central Sierra, but many are
also found in Sequoia and Kings Canyon.
The park cave with the greatest animal diversity is Clough. This
cave is probably home to seven species of invertebrates that live no
where else in the world. This includes a scorpion, a harvestmen and
several species of spiders. The cave is at low elevation and is warm
and seasonally wet. Tree roots provide food for many animals in
Clough. Guano from an active bat colony provides additional food for
invertebrates. There are several species of bats in Clough,
including the rare, Townsend's Big-eared Bat (Corynorhinus
townsendii).
Other park caves with unique species include Kaweah, Crystal,
Hurricane, Lilburn, and possibly White Chief and Panorama.
Sequoia and Kings Canyon maintain an ongoing research and monitoring
program to check on the populations of these animals. This involves
more than 60 "plots", small areas of park caves that are
checked for the presence or absence of the invertebrates.
Because of their sensitivity to the environment, cave-adapted
invertebrates can act as indicators of environmental problems or
changes. If park cave animals decline, it may point to other
problems in the park environment. Caves also often act as an
environmental refuge, providing a cool wet environment for animals
that are intolerant of dry, hot surface conditions. Often, the
closest relatives of cave dwelling animals may be found hundreds of
miles away where surface conditions more closely match those found
within the cave.
Without the use of lights, a trail, and warm clothes, caves would be
difficult, uncomfortable places for humans to visit. In caves there
is little or nothing for people to eat, and nothing with which to
make clothes or shelter. However, Many species have no such
requirements; they live out their lives without experiencing the
light of the sun or any change in temperature and humidity because
they reside deep within the winding maze of passageways that
constitute Crystal Cave. These animals have adapted to the unique
conditions inside Crystal Cave through countless generations.
Specialization allows them to survive in the cave, but also makes
them vulnerable to any disturbance or alteration of the cave
environment. Thus, the survival of these sensitive species and small
ecosystems depends on the proper management and protection of
Crystal Cave.
Troglobites have adapted and evolved to live exclusively in caves
and could not survive outside this environment. Often eyeless, they
lack pigment and may be different in other ways from their
surface-dwelling relatives. Troglobites include well-known cave
dwelling animals such as blind fish and white salamanders. In the
Western United States, where cave systems tend to be small and
isolated from each other, such troglobites do not occur. Instead,
Crystal Cave's troglobitic species are all small invertebrates,
animals without backbones.
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| A terrestrial isopod from Clough Cave in Sequoia National Park.
© NPS photo by Joel Despain. |
Park staff first noticed life in the cave stream in 1991. An isopod,
a small crustacean, related to sow bugs or roly-polys was found.
Fully adapted to the cave environment, with no eyes or coloration,
they survive by feeding on organic matter such as leaves and twigs
carried into the cave by the stream and swim using specially adapted
legs. A second unique species of troglobitic isopod lives on the
caves walls and floors. It was first noticed in 1995. This animal
also lacks eyes and pigment and feeds on organic matter. It has been
seen in only three rooms in the cave and is considered to be rare.
Other troglobites in Crystal include a unique species of white
millipede that feeds on organic matter and is often seen near bat
guano or mold. An eyeless centipede lives in the cave but has been
seen only one time. Centipedes are predators and the Crystal Cave
species probably feeds on the animals listed above. In areas with
roots Homopterans can be found. These animals feed on the plant
juices found in the roots. This is the newest addition to the known
Crystal Cave fauna. The Homopterans were first noticed in 1997. Most
of these species are probably endemic to Crystal Cave.
Troglophiles survive and can complete their life cycles in caves,
but have not adapted to the cave environment so completely that they
cannot also live on the surface in another suitable environment.
Crystal Cave's troglophiles include at least ten species of spiders.
Commonly seen, especially on the "Wild Cave" tour, is Nesticus
sylvestrii. These small, light-brown spiders weave webs composed
of dozens of individual strands spun inside cracks along the cave's
walls. Their prey includes other troglophiles such as fungal-gnat
flies and small, silver-colored springtails from the family
Collembola, Crystal Cave's most common inhabitant.
Another interesting spider is a representative of the genus Pimoa.
It is one-half inch across and has a shiny black surface with large
brown spots and spins large, tangled webs. These arachnids live only
near the cave's entrance, where small amounts of light penetrate.
This particular species occurs in several other cave entrances in
the Yucca Creek drainage near Crystal Cave, and ten miles to the
north, in Kings Canyon National Park, a closely related but separate
species can be found in another group of caves.
Other troglophiles living in Crystal Cave include at least two
species of millipede, one of which is bio-luminescent, creating its
own light with glowing body parts. Crickets with very long antennae
from the genus Tropidischia are uncommon, but can be found
throughout the cave as well.
Cave-dwelling species of bats constitute the most well known
trogloxenes. Small groups and solitary individual bats can be found
within Crystal Cave, particularly in the passages of the Catacombs
and near the cave entrance at dusk and dawn. All bat species in
Sequoia and Kings Canyon National Parks eat night-flying insects.
Because of the amount of energy required for flight and metabolism
in small mammals, bats must eat huge numbers of these invertebrates.
In a study in the Midwest, a single bat was found to have consumed
more than twenty thousand mosquitoes and fifty thousand moths in one
summer. By eating these insects, bats play an essential role in
maintaining a natural balance of animal populations and have the
additional benefit of keeping mosquito populations comparatively
low.
The little brown bat, Myotis lucifugus, the big brown bat, Eptesicus
fuscus, the California myotis, Myotis californicus,
and the rare Townsend's big eared bat, Corynorhinus townsendii
are believed to regularly use Crystal Cave as a daytime home, though
only small numbers are ever present. The long-eared bat, Myotis
evotis, the western pipistrelle, Pipistrellus hesperus,
the pallid bat, Antrozous pallidus, the mexican free-tailed
bat, Tadarida brasiliensis mexicana, and the lump-nosed bat, Corynorhinus
rafinesquii may also occasionally visit Crystal Cave.
Another trogloxene is the Ensatina salamander, Ensatina
escholtzi croceator, which is black with orange spots and can be
found in moist areas near the cave's entrances. When it is hot and
dry in Cascade Creek Canyon sometimes four or more of these colorful
salamanders can be found near the Ensatina Entrance to Crystal
Cave. Rodents, including the brush mouse, Peromyscus boylii,
the deer mouse, Peromyscus maniculatus, and the dusky-footed
woodrat, Neotoma fuscipes, are rarely seen but are believed
to be common due to the many acorns and droppings they leave in the
cave. The food that these rodents leave behind helps the other
animals in the cave to survive.
Large mammals also make use of the cave. Black bears, Ursus
Americanus, may have hibernated in the cave before it was so
frequently used by people. Mischievous ring-tailed cats, Bassariscus
astutus, occasionally forage for food inside and near the cave's
entrances. Humans, Homo sapiens sapiens - because our species uses
caves, for shelter, religious purposes, scientific research or
simply for fun and entertainment - are also considered to be
trogloxenes.
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