Bats belong to particularly protected fauna. These are mammals with a very important ecological role: in the vertebrates they are the main nocturnal predators of insects, including many species that are harmful or harmful to humans.
They are also very sensitive to environmental alterations caused by man, and for this reason many species are in a precarious state of conservation.
In June 2009, the municipal administration of Passerano Marmorito, recently settled, became aware of the presence of a large colony of bats in the building in Via Maestra in the past used for school use and the subject of recent restructuring for a new destination.
The Regional Bat Center was notified and, on 27 June 2009, an inspection was carried out: on the first floor of the building, on a wall where the plaster had peeled off, there was a reproductive colony of smeared vespertilio (Myotis emarginatus), a small bat, specialized in predation of flies, spiders and caterpillars of lepidoptera.
From a quick photo count, there were at least 354 specimens, but the total number was certainly greater, since bats arranged on the surface of such narrow aggregations normally hide other specimens.
It was learned that the bats had previously used the basement of the building, then abandoned because of the disturbance due to the renovation works.
Given that the colonies of bats can not be moved (they would immediately disperse), the location on the first floor made it difficult to reconcile the presence of bats with the anthropic use of the building. It should also be noted that the behavior of the bats in the choice of artificial shelters is still partly unknown and this meant that, in order to solve the problem, we had to proceed by trial.
During the spring of 2010, interventions were put in place to encourage a return of the bats in the cellar (reopening of closed access in the context of previous works), and others to increase the suitability to accommodate bats of the attic (obscuring a skylight to make darker the interior and placing rough wooden planks to facilitate the grip): if the colony had moved to the basement or the attic would have been much easier to make compatible the presence with the needs of human use of the building.
At the same time, the suitability of the room adjacent to the one used in 2009 has been improved (covering a portion of wall with a fine plastic net); it was believed that in this compartment it would be easier to manage the colony, being equipped with a potential access for bats and easily isolated from the rest of the building. In the following breeding season the specimens occupied this very room; the same occurred in 2011.
In order to evaluate precisely how many specimens there were and to acquire information on how they moved between the shelter and the external environment, evening surveys were carried out.
To get outside (and at dawn, to return to the building) the bats had two possibilities: to go through a French window located in the room used during the day or through a window in the attic, reachable through an internal window , connecting the first floor of the building with the attic. In front of this and the two openings, video recording equipment has been positioned in dark conditions (a thermal imaging camera and two high-sensitivity cameras that use infrared LED lighting).
Examination of the video material showed that all the specimens came out of the shelter from the first floor to the attic, to then use the window placed at that level.
The behavior of the bats complicates the management of the site: if they had used the French door in the same room used as a shelter would have been sufficient to isolate this volume, or a part of it including access, and allocate it to bats, thus eliminating interference with the anthropic fruition of the rest of the building.
Another solution was needed.
It was decided to set up a new compartment suitable to accommodate the bats, which was easy to discover for the specimens and placed so that their transits did not interfere with the anthropic use of the building.
The works were carried out in the spring of 2012: the room that had housed the colony in 2009 was divided with plaster walls, to isolate a portion to be allocated to the bats.
Inside this a window has been opened to put in direct communication the room and the attic, while the existing passage between the attic and the floor has been walled up. The new opening came to be a few inches from the previous one: one could therefore be sure that the bats would immediately find the new passage and this would obligatorily take them to the space they intended.
In the small room, areas had to be set up for the purpose and, for this purpose, fine plastic mesh and polystyrene panels with a rough surface were used. The network has been placed on plasterboard walls; the panels both on the walls and on the ceiling of the room, as well as inside the attic.
Inside the room has been created an opening that gives on the attic, where is the window that the bats used to come and go from the site, the colony is back in the building, but has not used the room set up for it, located in the attic, about two meters from the window to access the room. For the support the specimens used the door of the attic, in rough wood, or, alternatively, of the adjacent wall. Unfortunately, in that position, it was impossible to access the attic without causing the flight of the specimens.
The room set up for the colony, and deserted by it, however, gave a surprise: some specimens of greater rhinestone (Rhinolophus ferrumequinum) took to frequent the building, moving alternately between the room dedicated to the bats, the attic and the cellar. For chiropterologists committed to protecting the colony of smeared vespertilio it was a great consolation prize: the greater rhinophor is a large-sized chiroptera, predator of coleopterans and lepidopterans, and is a threatened species, which requires, compared to the smeared vespertilio, attention of conservation even more stringent.
But why did the colony of smeared vespertilio avoid the space that had been dedicated to her?
The suspicion came about that the polystyrene or the plasterboard near which the net had been placed for the support could for some reason be unwelcome to the species. Given that in the previous years the same type of net, placed on the masonry wall, had been used at the colony, during the following winter we proceeded to create a network covered area on the ceiling of the room dedicated to bats, which is not in plasterboard, but masonry.
In 2013, finally, the breeding colony settled in the compartment dedicated to it, positioning itself completely on the ceiling network. On 13 June 2013 its pre-breeding consistency (without the small ones of the year) was equal to 954 copies, counted by video footage during the evening exit from the shelter: it is one of the major colonies of the species known in Italy!
On the same day, in the attic, 4 specimens of greater rhinestone were observed.
How will this story continue? There are still many things to be discovered about the bats that frequent the site, but it is certain that the building, once a kindergarten and elementary school in Passerano, has become an environmental asset, and that men and bats can live in it.
• The operations described were made with the contribution of the Fondazione Cassa di Risparmio di Asti.