Cave Animal of the Year

Meet the 2023 USA Cave Animal of the Year:
Ceuthophilus Cave Crickets!

Perhaps you’ve seen it as you’re crawling near the entrance in a cave: the hop, hop of something moving. What is it? You take a closer look and see something that makes you smile—a cave cricket!

 

There are a lot of different cave crickets throughout North America, including at least 33 species in the genus Ceuthophilus. They have an oblong, humpbacked body with strong hind legs and very long antennae. They do not have wings and they do not have ears. Instead of hearing sound, they feel vibrations from the hairs on their legs and with th eir long antennae.

Welcome to the USA Cave Animal of the Year for 2023!

We want to help increase awareness of the amazing creatures that live underground by featuring a different cave animal each year!

Why pay attention to cave animals?

We marvel at the beauty of caves, but many people don’t think about those caves being home to an amazing diversity of animals. Some of these animals have interesting adaptations to live in a world of complete darkness and often scant food resources. Worldwide, there are many species of animals that live in caves. Cave Animal of the Year seeks to increase awareness of these fascinating animals and the importance of caves as their homes.

Getting to Know Ceuthophilus Cave Crickets

Cave crickets start out as eggs. They grow slowly, molting whenever they start to grow too big for their exoskeleton. Once they molt, they look like bigger versions of themselves. Once they become adults, they don’t live very long, just long enough to mate and lay eggs, creating the next generation of cave crickets. We do not know a lot about how many eggs they lay, but it may be 2-6 at a time in loose soil. Throughout their lifetime, they may lay anywhere from 30-60 eggs. And how long is that lifetime? Some cave crickets may live just one year, but others may live closer to two years.

The vast majority of Ceuthophilus cave crickets are not considered troglobitic, instead they are trogloxenes - animals that use caves but do not complete their entire lifecycle in a cave. Cave crickets typically exit caves at night to find food. They’ve also been observed molting and mating outside of cave entrances as well as inside caves. The guano and eggs that cave crickets leave inside of caves is extremely important for the troglobitic species that live deeper in the cave and spend their entire lifecycle underground.

We humans have been hanging out with cave crickets for a long time. There is a carving of a cave cricket in France that is at least 12,000-17,000 years old.

 

Where Can I Find Cave Crickets?

Ceuthophilus crickets are generally found in caves, but not always. Within caves they are often found on the walls and ceilings, but sometimes under rocks, too. Some of them will only go into caves occasionally and will hang out under rotting logs, rocks, in boulder fields, and other habitats that avoid sunlight. Most crickets will live in caves most of the time, only going outside to forage every few days. A few of them are more cave adapted and never leave the cave. It usually depends on the species and what is available in the surrounding habitats. Most crickets require a relatively constant temperature and humidity, which is why caves are preferred over other habitats. The family Rhaphidiphoridae is worldwide and the genus Ceuthophilus occurs in Canada through to Mexico.

What Do Cave Crickets Eat?

Cave crickets are omnivores. They eat what is available, and have been observed feeding on plants (fruit, grasses), meat (tuna fish), mushrooms, and human/junk food leftovers. Like many invertebrates, they switch between food sources multiple times throughout a night in order to ensure their dietary needs get met. Crop studies in New Mexico indicate much of the diet of crickets found near the cave entrance consists of green plant materials (leaves, grasses). Foraging range studies in Texas show that crickets painted at cave entrances travel over 100 meters from the entrance as part of their nightly travels, and also that they travel overland from one cave to another quite frequently.

Why are Cave Crickets Important?

Cave crickets forage outside of the cave, then come into the cave where they leave guano, exoskeleton sheds, eggs, and their own bodies after they die. These are sources of nutrients for cave-limited fauna. Since there is no primary production in the majority of caves, the nutrients that trogloxenes like bats and crickets bring in, along with that from flooding, is critically important for the ecosystem. In particular cave crickets travel to diverse areas within a cave, spreading these sources of nutrition in different ways than bats and floods. At least one endangered ground beetle genus, Rhadine, is known to specialize on cave cricket eggs. Cave crickets use their ovipositors to lay eggs into small holes in the clay or silt walls, and the cave-adapted beetle ‘sniffs out’ the tracks where the crickets have walked and sometimes finds the hole with the nutrient-rich egg.

Conservation of Cave Crickets

Similar to many species that mostly utilize a certain type of landscape (that with caves, or forests with cliffs and other damp, dark places), the primary threat to cave crickets is habitat destruction. When cities and farms expand into wildlands, areas that were formerly forests and fields are turned into monoculture ecosystems. These newly altered systems may support a few cave crickets that are able to ‘eek by’ in small pockets of trees or human dwellings, but the vast majority of the population does not survive.

Fortunately for cave crickets, while they do not have wings, they are still quite mobile, and it’s possible that even small pockets of forests or wildlands can serve as links between better habitats. Population genetic studies of this genus show source and sink populations as well as widespread genetic communication across the landscape. Thus as long as there are enough sources (e.g., large tracts of suitable habitat) the sink populations and intermediate patches of habitat may be viable and even important in the landscape-scale conservation of the species.

From a caver’s perspective, we can help conserve cave crickets as we conserve and maintain cave entrances - by keeping a buffer of natural vegetation around the entrance that is as large as possible. Crickets use the area immediately around an entrance to forage, and use smaller patches of habitat between the larger areas to travel between sites and maintain their genetic diversity. On the smallest scale, as we travel through the cave, we can do our best to move slowly, particularly through entrance areas, so as not to crush these important invertebrates!

Many thanks to Jean Krejca and Shiloh McCollum for writing information about cave crickets.

Learn more about cave cricket research in Kentucky and New Mexico started by Dr. Kathleen Lavoie in this great article:

Delving into the Cave Cricket Work by Dr. Kathleen Lavoie
By Kurt Lewis Helf

Subterranean Ecosystems

Subterranean ecosystems are often divided into major ecological zones that differ in abiotic factors, such as light, temperature, and humidity. These factors influence the types and numbers of organisms that occur in a given ecological zone. Caves are the most well-known examples of subterranean habitats. Caves can be divided into three major ecological zones.

The entrance zone marks the boundary between the surface and subterranean habitats and usually contains more species as well as greater variation in abiotic conditions, particularly temperature and humidity, compared to other zones. This zone is confined to the immediate area around cave entrances where light penetrates. Many species of plants and animals can be found in the entrance zone.

The transition zone (also called the twilight zone), marks the transition from the surface to subterranean habitats and connects the surface-dominated entrance zone with the dark zone. The transition zone is characterized by decreasing levels of light and habitats that are influenced by surface environmental conditions to a lesser extent than the entrance zone. Few plants grow in the transition zone, but many species of animals can exist.

Finally, the dark zone is the section of cave that lacks light completely and where environmental conditions are the most buffered from surface variability (i.e., conditions are usually the most stable). This deep cave environment is characterized by perpetual darkness, nearly constant temperature, and high humidity that is near saturation. No plant growth persists in the dark zone, and animals that exist here represent species that are most cave-adapted.
Subterranean habitats also can be divided vertically into distinct regions based on depth from surface and saturation with water. Each of these zones may host distinct communities of organisms.

Nearest the surface is the epikarst zone, which typically consists of networks of flooded or partially flooded cracks and crevices in bedrock and exists between surface and lower layers of unweathered soluble bedrock. Epikarst communities are dominated by small aquatic crustaceans, such as copepods and amphipods, but can also include terrestrial species. Water percolates through the epikarst and eventually reaches the vadose zone that contains a cave stream. A cave stream may be entirely fed by water from the epikarst zone or may also be fed by a sinking surface stream.

The vadose zone is the unsaturated area between the epikarst zone above and the water table below. The vadose zone of a cave is the area that can be explored by non-diving cavers (that is, you don’t need SCUBA gear!).

Finally, the phreatic zone is the region of a cave system that is permanently saturated with water and often contains large cavities. Wells in karst areas often access groundwater within this zone. Ultimately water within cave systems emerges back onto the surface at springs or seeps.

The ecosystem underground has some important difference from an above-ground ecosystem. Light is generally very limited and often absent. Nutrients may be very limited, unless there is a stream running through the cave or lots of cave organisms, like bats, who deposit guano in the cave. Generally, cave ecosystems are seen as being simpler versions of above-ground ecosystems. There is still a lot to learn.

Adapting to Life In a Cave

Many different organisms can be found in caves and other subterranean habitats. Some are accidentally in caves, having wandered in, or fallen into a pit. These species are not adapted to living underground and will perish if they cannot find their way back to the surface. However, other species purposefully live in caves for some or all of their lives. These creatures must adapt to an environment that is dark, generally has stable temperature and high humidity, and often has low food and nutrient resources.

Some species visit caves only occasionally. They are considered temporary or transient visitors, or trogloxenes, that use caves for shelter, to raise young, or to hibernate. Although caves are important to trogloxenes, they cannot live their entire lives underground and must return to the surface at some point during their lives. Examples of trogloxenes include cave-roosting bats and cave crickets.

Other organisms are more permanent residents of caves and subterranean habitats. Some may be found only in the entrance or twilight zones. These organisms called troglophiles can complete their entire life cycles within caves but often do not exhibit morphological adaptations associated with life in total darkness. Troglophiles also can be found in many habitats on the surface. Some species of salamanders, spiders, and flies are good examples of troglophiles.
Finally, some organisms,troglobitesand stygobites, spend their entire lives in the dark zone of caves and other subterranean habitats. Many but not all of these species have evolved a suite of traits, termed troglomorphy, associated with life in the perpetual darkness of caves. These traits include loss or degeneration of eyes and pigmentation, elongation of appendages, and increased capabilities of non-visual senses, particularly touch, taste, and smell. Obligate cave species also tend to have slower metabolic rates and longer lifespans compared to their surface-dwelling relatives. Obligate cave species are broadly categorized according to habitat—terrestrial species are called troglobites (or troglobionts), while aquatic species are called stygobites (or stygobionts).

Cave Animals of the Year from Other Countries

Several other countries also celebrate Cave Animal of the Year.
Germany (Fire salamander)
Italy (Niphargus amphipods)
Australia (Glow-worms)
Brazil (Cave beetle Coarazuphium cessaima)
Austria (Fire salamander)
Switzerland (Fire salamander)

Previous USA Cave Animals of the Year

This is the fourth year for the USA Cave Animal of the Year. The NSS supports this worldwide initiative to bring more attention to the amazing creatures that live underground.

Learn about:
2022 Little Brown Bat
2021 Pseudanophthalmus Cave Beetles
2020 Great Basin Cave Pseudoscorpion

How You Can Participate

We need your help spreading the word about Cave Animal of the Year.

Please share this website address with friends and on your Grotto social media.

If you are lucky enough to find a cave cricket or other cave animal while caving, help others see it and learn about these cave species. We invite you to take a photo of the creature and post it on the USA Cave Animal of the Year Facebook page.

Have another great year of learning about and helping to conserve habitat for the fascinating animals that make caves their homes!