Caves and karsts are unique habitat type that harbor a diverse and unique taxa but currently imperiled by human exploitation. It has been a practice among conservationist to use a surrogate taxa in conserving and protecting habitat, in caves, among the numerous taxa what would be the best candidate?
I think species that cannot easily move away from a disturbance or with very specific habitat requirements would be most sensitive to anthropogenic pressures, such as invertebrates. Check out Clements et al., 2006, Limestone karsts of southeast Asia: imperiled arks of biodiversity and Clements et al., 2008, Using biogeographical patterns of endemic land snails to improve conservation planning for limestone karsts.
I agree with Marcelo and Kendra. While bats can definitely be indicative of a healthy cave they will also use caves that are not healthy. I have been in numerous caves that are basically dead with the exception of bats still using them as roosts. Arthropod fauna would be my choice due to their presence in every healthy cave and their lack of ability to move from cave to cave unless it is an interconnected system of caves. Using land snails would be good, however I have never seen any snails that live very far from the light zone in caves and that could be a consideration depending on what you are trying to determine.
In Florida the karst caves are mostly aquatic and accordingly have aquatic fauna. Crayfish are in most of them but species vary regionally. Isopods are a better indicator probably. However, monitoring is logistically limited to nearer parts of the caves and hydrological influences (e.g., velocity and water quality, back-flooding) may be major influences on population sizes at any given time. I can provide contacts to experts.
The question is perhaps to broad to be resolved with a simple answer. Certainly the relative health and cave conditions will certainly influence a selection. Dr. Steve Carothers of SWCA Consultants (Flagstaff, AZ) has more than 30 years experience and would be a logical data source given his experience with cave invertebrates, endangered and otherwise.
A maxim I have found useful is 'look after the habitats and the species will look after themselves'. In south-west Australian limestone regions, lowering of the water-table is the main issue, and this has put some aquatic cave invertebrates in jeopardy.
Having said that, one looks for the 'keystone species'? I agree bats are important - many other species depend on them, eg in food-chains based on dung - this might include annelids and spiders. Above ground, there are a whole series of sub-systems worthy of conservation. In northern England the 'grykes' in limestone pavements constitute mini-ecosystems in themselves; it would be difficult to identify keystone species but ferns might be candidates.
It will be depending on the type of cavity (geological origin, age, etc) as well as its geographical location. Of these features, among many others, depend on the type of cave fauna (troglobia) you can find and trace protection plans. Bats use the cavities only as daytime shelter, but there are a large number of invertebrate species that are unique inhabitants of this ecosystem and die at the slightest modification and environmental deterioration.
It is customary to always take vertebrates when thinking protection plans because they work very well as "umbrella species" under the shadow of which many other species are protected and even entire ecosystems.
Check out work by Danny Tang and/or Brenton Knott on Australian systems
Dear Dr., In my region of France (Alpes-Maritimes, Var departments) [email protected], 3 interesting groups of invertebrates are to be preserved in small cavities of underground (in karstic underground and also in underground of old churches and capels and of houses) and in caves: Orthoptera (Gryllidae and Dolichoderidae), Coleoptera (Carabidae) and Millipodes (Scutigerellidae, Blaniulidae, Iulidae). Best regards.
Hey Krizler
Very dependant on species and area. Karsts actually host numerous types of endemic faunal groups: on the outside of the karst (plants (i,e orchids, ferns, generinacae, Begoniaceae, urticaceae) and in the entrances of caves. In addition there are multiple vertebrate groups, especially reptiles and amphibians, though some endemic mammals, and birds are also known, additionally endemic invertebrate groups (i.e. snails) are also recorded.
Some of these taxa also specialise in the entrances of caves (especially the plant taxa). Then you have the troglodytes, troglophytes, etc. Cave faunal includes various insects, and other arthropods, in addition to cave fish and crustaceans which live entirely within caves. Bats are one of the only taxa that act to bring "energy" into the system, and are thus a vital component of functional cave ecosystems.
Some forms of disturbance will effect all karst life, other types of disturbance will only effect a subsample. For example, if the area surrounding the karst is deforested and planted with something like rubber it will effect the water-table and the temperature stability of the region. It is likely to cause the karst to become hotter and drier-and therefore effect all karst dependant taxa. So in terms of environmental disturbance using a number of taxa both on the karsts and within caves is a sensible way to understand the effect of these larger terms of disturbance
Collection of any individual species is only likely to really have an effect if it changes environmental structure or nutrient cycling sufficiently, i.e. collection of a few orchids is not likely to cause huge change unless other plants are also cleared, whereas the mining of guano, if sufficient to make the bats leave is likely to cut off the supply of nutrients to other species in the cave and so may have a detrimental effect on diversity within the cave.
If you are looking for the effects of climate change then choosing a number of different taxa with different sensitivities, and in a range of karsts with different levels of disturbance is important, as the majority of karst dependant species are likely to be poor dispersers, and the ability of a karst to buffer against climatic changes is likely to be a reflection of how intact the environment is (water table, vegetation height and density).
Because most caves are typically nutrient poor, troglomorphic invertebrates require some sort of nutrient input into the cave. This can be provided by surface input-mostly plant matter and dissolved molecules- during rainstorms and surface flooding, then species from the various trophic levels and taxa extract the nutrients, including predator-prey interactions.
Some troglophilic species are also critical for this cycle. Bats and guano are prime examples. In central Texas, we also use another troglophilic species, cave crickets, to assess the potential of a cave to support the troglomorphic fauna. Like bats, this species can be found in caves by the thousands and will leave the cave in large numbers at nightfall, returning before daylight. The crickets serve as a critical nutrient link between the surface and the cave.
So, you may want to consider determining the key biotic and abiotic inputs into the caves you are examining and score the troglomorphic fauna on rarity across a landscape, density within a cave or system of caves, and sensitivity to change (you could use average depth the species is found for this metric). Biotic and abiotic inputs have a critical role in supporting the long term survival of not just the troglomorphic species, but the entire nutrient cycle of the cave itself.
Hello Researcher:
As it can be seen arthropod fauna can be studied as surrogate species for conservation, as these animals are everywhere in our mother earth, variations in their abundance, richness, dominance if they are or arent troglobionts can tell you a lot that is happening in caves even we cant find bats. Simply let´s sample thoroughly the soil, walls and mud and a lot of data wil appear.
Go on with your research and tell us what you find.
Best wishes
Marcelo
Like Mary, I also agree with Marcelo and Kendra. Bats could provide nutrients for cave animals but that is exclusively for those coprophagous. If the cave is disturbed, the bats could easily move from one location to another, they could easily find new suitable cave habitats. Invertebrates, which dominated the subterranean ecosystem, have limited movement, most especially the stygobitic animals (cave-obligate aquatic species). They are very sensitive even to slight cave disturbance therefore they could be affected very easily. Moreover, endemism of this stygobites are very high. So considering everything, stygobites are overall more prone to extinction. Cheers!
Actually,
First of all, you must make a rapid assessment to the cave, to know what are species matter.
I doubt surrogate taxa work well with karst, where different groups of specialists live in very different habitats and never meet each other. You would need at least one surrogate per habitat! How about using physical variables instead: volume, height, presence and size of caves, etc,?
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