Bats on the Rocks
Last Updated: 20th May 2013
Bats on the Rocks
The interest in learning something more about bats came from a recent conversation held with a good fellow in the last Lisbon mineral show regarding the existing populations of bats in the Preguiça mine and in natural caves too close to some active limestone quarries in Alcobaça and Rio Maior region. There is contradictory information regarding the effective protection (or not) of the bats made by the local authorities for the protection of the nature. I think that the economic point of view wins almost all times…
I decided to do a brief search to verify the bat populations importance to the regional environment.
Much information about bats is available on the web but I focused my attention in a short article written by Luisa Rodrigues (Instituto da Conservação da Natureza) e Jorge M. Palmeirim (Departamento de Zoologia e Centro de Biologia Ambiental, Faculdade de Ciências, Universidade de Lisboa).
In addition to geological importance (and mineralogical importance for us, of course) some caves and inactive/abandoned mines have a high biological interest for harboring unique animal communities.
Why is important to talk about ba ts
There are twenty four bat species in Portugal, about half lives in caves, mines and others underground during great part of the year with some species completely dependent of these environments. The ecological importance of these populations is very high, since they consume large quantities of insects, because insects could become pests for agriculture or be vectors of diseases, it is easy to understand how important bats are.
The lack of organic matter in the caves and inactive/abandoned mines is a limiting factor of great importance; cave bats are often the main importers of organic matter essential to the maintenance of the invertebrate communities of the caves and old mines; the disappearance of a population of bats can cause the destruction of some of these rare communities.
Some bat species are under threat
Although some species are very abundant, most of them in our country have a small and fragile population. The latter are usually the bat caves, nine being classified as in danger of extinction in the Red List of Portuguese Vertebrates.
This situation occurs not only in Portugal. In several European countries bat populations have suffered a dramatic decline in recent decades. The density has decreased, the distribution areas have been reduced and some countries have even lost many species of their fauna.
Why our bats are threatened
In addition to the fragile population resulting from a very low reproductive rate, and in some cases, a large concentration of population due to dependence on a limited number of shelters, there are other reasons that have caused this dramatic situation:
- Disturbance of the shelters - the disturbance of the shelters is probably the most important cause of the decline of cave bats in Portugal. Until a few years ago, superstition and technical difficulties meant that the caves and old mines were very rarely visited. The rapid cultural changes in the Portuguese society are eliminating the superstitions that for millennia avoid disturbing the populations of cave bats.
Every year thousands of people are entering in the caves and abandoned/inactive mines occupied by bats and this number seems to continue to grow.
The main threat to these populations is the many sporadic visitors including national and foreign mineral collectors who visit our mineral localities which are quite unprotected due to lack of adequate legislation.
There is a few number of caves, mines and bats demanding microclimatic characteristics and location of shelters that select, their availability is a limiting factor of the abundance and distribution of cave species. We are already seeing the destruction of some important underground shelters in the country.
- Destruction of biotopes power - having large energy need, our bat species depend on hunting areas with high densities of insects.
The reduction and transformation of the natural habitat areas certainly affect the bats that feed on them, being particularly serious the loss of wetlands and hardwood areas.
- Use of pesticides - poisoning with pesticides seems to be an important factor in mortality of bats, but their real impact on populations is difficult to assess. Pesticides are also very harmful to them as they decrease, sometimes dramatically, available food resources for insectivorous species.
What has been done to protect the bats
The preparation of the national strategic plan for preservation of the cave bats allowed us to assess the status of species at a national level and propose concrete measures for their protection. The ICN (national institute for nature conservation) has been implementing the recommendations of the plan. In addition to direct measures of protection of some shelters, monitoring has been undertaken of the main breeding and hibernation colonies and developed several studies applied to the protection of these species.
However, all efforts depend on the participation of all, since these species greatly depend of changing its public image.
What can the speleologists, geologists, mineralogists and mineral collectors do
As mentioned, the disturbance of the shelters, particularly in the breeding seasons (April to July inclusive) and hibernation (December to February inclusive), is one of the main reasons for the threat of the species. For this reason, the selection of shelters that are visited during these times, especially with large groups should be carefully evaluated.
However, there are some rules that should always be considered:
- Avoid visiting the areas of the caves or inactive/abandoned mines that harboring bats.
- When bats are found during the visit, leave this area as quickly as possible.
- Avoid making noise and lighting the animals - do not handle bats, even when they are in lethargy.
For an effective preservation of the bats, the help that the speleologists, geologists, mineralogists and mineral collectors can provide is extremely important: reporting the location of the new populations or any problem in the caves/old mines will assist ICN to monitor the underground shelters for better preservation of these amazing creatures.
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