Knowledge is power: How can we make cave tourism more environmentally friendly?

A new study in Nature Conservation presents a literature-based dataset on the ecological status of 265 show caves in 39 countries across the world.

Throughout history, people have used caves for a number of reasons: as shelters, places for rituals, food storage, and, in more recent times, as touristic attractions.  In these so-called show caves, visitors can experience the natural beauty of caves, usually by following a guide on constructed, artificially lit trails.

But caves are also very fragile ecosystems, bursting with underground life. They are home to numerous invertebrate and bat species, including ones that are threatened or endemic. The human disturbances caused by the changes in the infrastructure and environment, coupled with the influx of tourists, often affect the ecological processes and, consequently, these organisms. But how much do we know about the influence of tourists on cave ecosystems?

According to a new study in the open-access journal Nature Conservation, not enough.

Apart from affecting subterranean invertebrates, the artificial lighting and noise related to tourist visits may also affect the life of bats, making it harder for them to reproduce or overwinter in caves.

Going through more than 1,000 scientific papers, an Italian team of scientists, led by Marco Isaia and Elena Piano from the University of Torino, prepared a literature-based dataset relative to the knowledge on the ecological status of 265 show caves in 39 countries across the world. Their database includes a georeferenced set of show caves, where researchers have evaluated a number of environmental indicators that help monitor the impact of tourism and its related activities on subterranean ecosystems. They also list cave characteristics for each cave, including its natural heritage that attracts tourists.

There are many ways in which tourism can disturb life in a cave. For example, the presence of visitors may help increase cave temperature, which, combined with the increase of CO2 air concentration caused by tourists’ breath, may enhance carbonate dissolution, damaging geological formations. Moreover, tourists can carry pollutants and propagules of microorganisms into the cave through their clothes and hands, which then land on geological formations, in the water, in the air, and on the ground. Apart from affecting subterranean invertebrates, the artificial lighting and noise related to tourist visits may also affect the life of bats, making it harder for them to reproduce or overwinter in caves.

The dataset published in Nature Conservation set a baseline towards the integrated and multidisciplinary study of the impacts caused by tourism on these fragile ecosystems, but the research team points out that much remains to be done. For example, they found out that there wasn’t enough research on show caves outside of Europe, or on the possible impacts of tourism on the subterranean fauna in the context of climate change.

Ultimately, the data in this study can help managing authorities come up with guidelines that will allow a sustainable touristic development of show caves, not only from an environmental perspective, but also from an economic and social point of view.

“Overall, this data paper could fill the lack of awareness towards the fragility of the natural heritage of show caves to favour a sustainable touristic use that would guarantee their preservation for future generations as well as the economic development of local communities”, the authors conclude.

Research article:

Piano E, Nicolosi G, Mammola S, Balestra V, Baroni B, Bellopede R, Cumino E, Muzzulini N, Piquet A, Isaia M (2022) A literature-based database of the natural heritage, the ecological status and tourism-related impacts in show caves worldwide. Nature Conservation 50: 159-174. https://doi.org/10.3897/natureconservation.50.80505

All images are from Bossea show cave in Italy, by Simone Marzocchi.

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Guest Blog Post: New Area of Importance for Bat Conservation in Honduras

The recognition of the “Ceguaca, la Mujer de los Juncos” locality comes as a result of research work – published last year in Subterranean Biology – which produced the first checklist of bats for Santa Bárbara


Guest blog post by Eduardo Javier Ordoñez-Trejo and Manfredo Alejandro Turcios-Casco


Bat populations are threatened due to fragmentation and loss of their habitats. Meanwhile, dry forests are some of the least studied and most threatened ecosystems in Honduras, and similarly, so have been the caves.

We had to walk at least two hours to reach either of the caves in El Peñon or Quita Sueño, so we would take our full equipment: for camping, cooking and studying bats.
Photo by Hefer Ávila

Caves are important reservoirs of species, as they offer perks no other habitat can provide at once: a refuge from predators, inconstant weather, and a critical venue for social interactions, reproduction, hibernation, roosting and nutrients. In order to protect bat populations, the Latin American and Caribbean Web for Bat Conservation (RELCOM) supports the establishment of Areas of Importance for the Conservation of Bats, abbreviated as AICOMS (Spanish for Areas with Importance for the Conservation of Bats) .

It was at least a two-hour walk between the caves of Monte Grueso and the caves of El Peñon. The final stint, though, included a swim across Rio Ulúa, one of most extensive rivers in Honduras.
Photo by Hefer Ávila

Together with biologists of the National Autonomous University of Honduras (UNAH) and local community members, we provided the first ever checklist of bat species in the Dry Forest of Ceguaca, Santa Barbara (Honduras), and described the importance of two caves in the area for bat conservation based on species richness. We published this study last June in Subterranean Biology.

The study is openly accessible in Subterranean Biology

We found that caves in Ceguaca are inhabited by at least 23 bat species of four families, which represents approximately a fifth of all species known from Honduras. Their inhabitants include several threatened species like the hairy-legged vampire bat (Diphylla ecaudata), one of the three existing vampire bats, and rare species with few official records in the area, such as Schmidts’s big-eared bat (Micronycteris schmidtorum). These caves may also represent a critical site for roosting and nursing. During our study, we managed to record pregnant and lactating females of several species, as well as reproductive males.

The certificate issued by RELCOM recognising the caves in Ceguaca as an Area of Importance for the Conservation of Bats, dated 6th March 2020

“It feels wonderful to see that our work has had great results and that with our efforts, we established an area where bats will be protected and studied. This certification also includes the name of Roberto Castellano, an elder member of the community of Ceguaca, who helped us during the fieldwork as our guide. He was a great conservationist of this area and protector of the caves. Unfortunately, he passed away during the study, however, due to his enormous contribution, we dedicated our article to him and included him as part of this AICOM success.”

José Alejandro Soler Orellana, co-author of the study.

Using what we learned in Ceguaca’s caves, we approached the Program for Bat Conservation of Honduras (PCMH) and showed them the evidence the locality was indeed a precious place with a spectacular bat diversity. Consequently, thanks to our collaboration with the PCMH, the site was effectively declared as an Area of Importance for the Conservation of Bats by RELCOM on 6th March 2020. 

This is an enormous step for bat conservation in the country. Bat conservation efforts should focus on studying and protecting these and other important habitats. We also need to make sure that local people appreciate the important role the bats play in the ecosystem.

A close up of a spider

Description automatically generated
We captured this adult Pallas’s long-tongued bat (Glossophaga soricina) female in a cave in Monte Grueso. She must have been returning to the cave after spending the day pollinating local plants. During these surveys, we found trees with opened flowers of Mexican calabash (Crescentia alata).
Photo by Hefer Ávila

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Research article:

Turcios-Casco MA, Mazier DIO, Orellana JAS, Ávila-Palma HD, Trejo EJO (2019) Two caves in western Honduras are important for bat conservation: first checklist of bats in Santa Bárbara. Subterranean Biology 30: 41–55. https://doi.org/10.3897/subtbiol.30.35420

Out of the darkness: A new spider found deep within an Indiana cave

Lead author Marc Milne in the Stygian River Cave and a male specimen of the newly described Islandiana lewisi 

Spiders are ubiquitous within our forests, fields, and backyards. Although you may be used to seeing the beautiful yellow and black spiders of the genus Argiope in your garden, large ground-scurrying wolf spiders in your yard, or spindly cellar spiders in your basement, this new sheet-web-building spider is probably one you haven’t seen before. The reason is that it’s known from a single cave in the world, Stygeon River Cave, in southern Indiana.

The University of Indianapolis assistant professor, Dr. Marc Milne, described the rare species in the open access journal Subterranean Biology with the help of a University of Indianapolis alumnus, Elizabeth Wells, who illustrated the spider for the manuscript.

Sheet weavers, also known as dwarf spiders or money spiders, are minute creatures growing no larger than a few centimetres in length, which makes them particularly elusive. Their peculiar webs are flat and sheet-like, hence their common English name.

Female of the new species Islandiana lewisi

The new spider, Islandiana lewisi, is an homage. Milne was shown the spider by a fellow scientist, Dr. Julian Lewis, who noticed the critter on one of his many cave expeditions. In appreciation for his help, Milne and Wells named the spider after Lewis.

This is the fifteenth species in its genus (Islandiana) and the fifth known to live exclusively in caves. It has been over 30 years since the last species has been added to this group.

At about 2 mm in size, Islandiana lewisi is thought to feed on even smaller arthropods, such as springtails living in the debris on the cave floor. It is unknown when it reproduces or if it exists anywhere else. The spider is likely harmless to humans.

The collectors of the spider, Milne and Lewis, described the hostile conditions within the cave, which the new species calls home: “because the cave floods from time to time, the insides were wet, muddy, slippery, and dangerous to walk on without the proper equipment.”

Milne and Lewis found the spider in small, horizontal webs between large, mud-caked boulders in the largest room in the cave. It was collected in October 2016 with the permission of the landowner.

Milne hypothesized that he had collected something special, stating, “I didn’t know what the spider was at first, I just thought it was odd that so many were living within this dark cave with no other spider species around.”

After returning to the lab and inspecting the spider under a microscope, Milne initially misidentified the species. However, when he re-examined it months later, he realized that the species was indeed new to science.

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Original source:

Milne MA, Wells E (2018) A new species of spider (Araneae, Linyphiidae, Islandiana) from a southern Indiana cave. Subterranean Biology 26: 19-26. https://doi.org/10.3897/subtbiol.26.25605

Saving the Underworld: Clarifying the subterranean fauna classification for improved conservation

Inevitably, many habitats, including the particularly vulnerable subterranean ones, will continue being erased from our planet as a result of human activities and interests. The challenge is to protect the ones that are the sole habitats to certain organisms, so that their species are safe from extinction. Hence, it is essential that the distribution of every each one of them is clearly defined.

Brazilian scientists Prof. Eleonora Trajano, Universidade Federal de São Carlos, and Prof. Dr. Marcelo Rodrigues de Carvalho, Universidade de São Paulo, discuss the current classification system, its application and complexities in a paper published in the open access Subterranean Biology.

9759_Image 2Nowadays, there are three categories of subterranean fauna accepted. Troglobites live exclusively underground and are usually characterised with reduced or lacking eyes and pale or transparent colors; troglophiles may live both in caves and on the surface, with individuals commuting between these habitats and promoting genetic interchange between subterranean and surface populations; trogloxenes use caves regularly, but must leave them periodically in order to complete their life cycle.

Throughout the years, many alterations and subdivisions have been applied to the classification used when determining whether a cave organism belongs exclusively to the subterranean habitat, or not, before concluding these three groups, also known as the Schiner-Racovitza system. It is important to separate them properly, since the destruction of a habitat to an endemic troglobite, for instance, would immediately wipe out its whole species, as it would be impossible for the animals to move away.

However, many historic publications do not feature enough details about the described species’ distribution, nor identification of the used classification, so that the information is unreliable. Furthermore, there have been times, when people have been even afraid to survey the underground habitats, led by beliefs and associations linking caves to the “World of the Dead”.

In their paper, the authors conclude that the only way to define the species status of subterranean organisms with certainty is to study each species’ dynamics over a period of at least three years, since animals may migrate on a seasonal and/or non-seasonal basis. Also, scientists need to study thoroughly the area outside the surveyed cave, while testing for sampling sufficiency at all times.oo_124566

“When employing classifications of subterranean organisms, especially for conservation purposes, these conditions should be checked for reliability of the status attributed to them,” say the authors. “Misplacing these organisms within the Schiner-Racovitza categories impairs the efficiency of such policies.”

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Original source:

Trajano E, Carvalho MR (2017) Towards a biologically meaningful classification of subterranean organisms: a critical analysis of the Schiner-Racovitza system from a historical perspective, difficulties of its application and implications for conservation. Subterranean Biology 22: 1-26. https://doi.org/10.3897/subtbiol.22.9759