Ferrantia, Volume 31: Proceedings of the 3rd European Bat Detector Workshop 16-20 August 1996, Larochette (Lux.)

About this book

Language: Eight papers in English, one in French and one in German, all with trilingual abstracts in English, French, and German

Proceedings of the 3rd European Bat Detector Workshop contains the following ten papers:
 

Michel Barataud & Yves Tupinier: Ballades dans l’inaudible Univers acoustique des chiroptères d’Europe
During the last years a rapid development of the knowledge on the bat calls has been noticed. The instruments needed for this have become lighter in weight and financially accessible for a greater number of zoologists. Considering this evolution it became useful to produce a compilation of  sound references and a guide to help naturalists using detectors. This is now available as compact disks together with a booklet produced by Catherine Bouchain and Jean Roche and published by Editions Sitelle and the Linnean Society of Lyon. As the items based only on heterodyne records are the most numerous, a whole disk is dedicated to this method with a detailed text to give aids in identifying those species for which the method is valuable. The second disk is dedicated to time expansion for 25 European bat species. The structures of the calls and their variability depending from behaviour or habitat are shown. These sound documents are coming with a booklet for use in the field and a volume giving details of the structures based on acustic analysis, illustrated by many  graphs (spectral density, spectrographs,...). These documents being also destinated to a larger public.

Lars Pettersson: Time expansion ultrasound detectors
A short overview of different ultrasound conversion techniques is given. The time expansion technique is unique in the sense that it preserves virtually all characteristics of the original signal. This technique is described in detail, as are some of the basics of digital signal processing. A few examples of bat calls recorded with both heterodyne and time expansion detectors are given. The sound samples are replayed and compared in order to illustrate the advantages of the time expansion technique. Some new methods to further enhance the usefulness of time expansion detectors are also presented.

Reinald Skiba: Die Erfassung der Vorkommen der Nordfledermaus, Eptesicus nilssonii, in der Bundesrepublik Deutschland mit Hilfe von Ultraschall, Methodisches Vorgehen, Ergebnisse, Problemei
During the last years the distribution of the Northern bat, Eptesicus nilssonii, in the Federal  Republic of Germany was mostly clarified with the aid of ultrasound detectors. Organization of investigations, technique of recording, method of analysis, documentation of results and possibilities of confusion with other species are described and discussed. Also results of investigations about the geographic distribution of the Northern bat are shown and interpreted.

Matti Masing : Experience of bat monitoring with bat detectors in Estonia
A modification of a bat monitoring method, the Route Counting Method (RCM), has been worked out and tested by the Estonian Bat Group in recent years. Our aims were the following: 1) to work out a simple method for bat census in summer habitats; 2) to estimate bat populations in chosen monitoring areas (so-called monitoring stations) in Estonia. Three bat detectors (two of Skye Instruments SBR 1200, and one of Pettersson Elektronik D90A)  and pocket-size tape recorders were used to record bat calls for further analysis. The present Route Counting Method to monitor bat populations in summer habitats is based on counting of flying bats with bat detectors on monitoring routes. The method is a modification of a Line Transect Counting Method (LTC). On routes there are usually certain points where several bat  species often concentrate to feed. In these waiting-points the observer stops for 3 minutes to record  all species. Quantitative results of observations are achieved by dividing the route into segments with length of  50 m (in case of Nyctalus noctula 100 m). Species will be recorded separately within each of these segments. Data of countings will be transformed into relative data, by extrapolating them per 10 km. Thus, the data of different routes become comparable. For correct determination of species, visual observations are required, for which light midsummer nights in June—beginning of July fit best. On the basis of counting data, the Route's Monitoring Index and the Mean Monitoring Index will be calculated to quantitatively estimate the status of bat populations in monitoring areas.

The Route's Monitoring Index (RMI) presents the number of individuals + number of bat groups recorded per 10 km on a certain route. The Mean Monitoring Index (MMI) presents mean data of all routes studied. MMI values are quantitative estimations of bat populations for a larger area (e.g. Estonia). The MMI is only a relative index, which cannot be used to estimate exact bat numbers in certain habitats, as well as on the whole area of monitoring. On the basis ofRMI-s collected from monitoring routes located in different parts of Estonia, the MMI has been calculated. The MMI value, mean of 20 routes studied in Estonia in 1993-1994, was 25.7 individuals and 7.2 groups of bats per 10 km. This is a quantitative estimate of bat populations in Estonia concerning the study period. The present Route Counting Method is considered to be capable of quantitatively estimating the status of bat populations on a larger area. The Mean Monitoring Indices obtained "from certain areas during subsequent years, or subsequent longer periods should show in which directions bat populations actually change. MMI-s will show these changes quantitatively. Considering the important cumulative content of MMI, it could be even dealt as the Main Monitoring Index.

Christine Harbusch: Monitoring Bats in the Grand-Duchy of Luxembourg
The bat fauna of Luxembourg has been inventorized for the first time in a systematic way during the years 1991-1996. The methods applied were the use of an ultrasound detector, model D980 (Petterson, S), the inspection of attics and mist-netting in feeding habitats and in front of mating or hibernating sites. Until now, 19 species have been recorded. The distribution of these species and the best method to apply on the field work considering the time available and the surface to study  are discussed. It is shown that the results of such a brief survey are not sufficient to get a reliable knowledge on the status of the species.

Leif Gjerde: Methods and theories of monitoring bats in Norway
For the last four years NØBI have been trying to develop and identify methods of monitoring bat  populations with the use of ultrasound detectors. There are several factors making this difficult and  especially the human error of data sampling must be studied carefully. There seems to be no simple  solution for monitoring fluctuations in bat populations, and a lot of experimental work must be tried out first. Temperature seems to have a strong impact on bat activity. However, bat activity really reflects insect availability. Summers are short in Northern Europe, and so are the nights. Bats need to gain strength from the previous winter, reproduce and prepare themselves for the coming winter during  these short summers. The number of nights and hours in which foraging is possible will therefore strongly affect the population.

Rydell (1989) showed that Eptesicus nilsonii did not forage at temperatures lower than 6 °C. Furthermore, all bats in this study foraged at temperatures equal or above 10 °C. The number of nights with a temperature of ten degrees or more may then indicate the number of nights that are  suitable for foraging. When calculating the number of nights for a number of consecutive summers, and compare this with an average, it is possible to use this for explaining, in part, population fluctuations. Of course, such a PFN index (= Potential Foraging Nights) cannot be used for comparing between different areas, but will allow monitoring a specific population through time. I remain to check the threshold temperature for bat activity between regions and species to enable a more widely use of the method.

Leif Gjerde & Darko Kovacic: Bat survey by car transects in Luxembourg
In one night, a car was driven with a speed of maximum 60 kmh on a transect of 50,6 km in total. Two bat detectors were used to count bats, one fixed to 25 kHz and one to 45 kHz. A total of 129 bats of 4 species were counted. The most frequent species was the common pipistrelle bat  (Pipistrellus pipistrellus) with 103 encounters. It was mainly found in villages or over forest roads. 5 of 6 recordings of the serotine bat (Eptesicus serotinus) were made in or near villages. Only twice a noctule bat (Nyctalus noctula) and one Myotis species were registered.

W. J. R. de Wijs: Feasibility of monitoring bats on transects with ultrasound detectors
In 1990 an experimental study was started to test if point and line counts along transects could be used for monitoring bats. Later, this was incorporated into the Dutch Mammal Monitoring Programme. In 1995 counts on 10 transects resulted in 1682 recorded presences of 9 species. Each transect of 13-17 km consists of 20 points and 20 lines in between, on which bats are recorded. Counts are performed monthly from April-September. Transport is usually by bicycle. Ultrasound  detectors are tuned to approx. 40 kHz. Variables noted are presence, maximum number heard at one time and total number of registrations, for each point or line. Results from 6 transects have  shown that all three variables are strongly correlated, but that presence showed the least variation. It is therefore preferred for monitoring purposes, but has the disadvantage of possible saturation  (maximum is 100%). Results from points and lines were also strongly correlated, but variation at  points was smaller. Some species showed some seasonality in presence, resulting in variation being smaller in some  months than in others. This differed between species, so counts in different months seem necessary. The maximum presence per season showed similar variation as the mean presence per season.  Results indicate that by using approx. 100 transects, differences between years of 20-40%  (depending on species) or more can be detected. Monitoring bats this way, however, requires welltrained observers.

Markus Dietz, Ralf Frank & Jacques B. Pir: The Bat Fauna of the 'Grünewald' forest in Luxembourg: a methodology approach
Luxembourg authorities plan to cut the greatest ancient forest massif, the 'Grünewald' forest by a new motorway. To assess a maximum offaunistical data on forest dwelling bat species in this wood in a short time, different bat survey methods were used during summer 1996. The suitability of the different methods is analysed as the results and problems of this study are presented and discussed.

Dr. Robert Brinkmann & JGA Herman: The role of bats in landscape planning
Landscape planning is the most important planning instrument for nature conservation in Germany. One main objective is the protection and development of all animal and plant species in their natural habitats. The necessary basic information for implementing adequate conservation measures is obtained through habitat mapping. In addition, inventories are taken of different animal groups, for instance birds, dragonflies, and more recently of bats. This proceedure is necessary not only because bats belong to the most threatened groups of animals in Germany, but also because they are good indicators of those habitats which have a high value for other animal species. For a comprehensive inventory of bats in a planning region, the application of different methods, for instance netting, inspection of attics and bat detector work, is necessary. Within any combination of methods, survey work with the bat detector will be a most important tool in gaining an understanding of the function of the different types of habitats as hunting areas, flight paths and roosts, and their interconnections. As an example of how data on bats can be integrated in planning, the local landscape plan for Bad Nenndorf is described.

Here a total of 7 bat species were recorded, using a combination of methods. From the survey results, concrete measures for the protection of roosts, hunting habitats and flight paths could be arrived at and these could be implemented precisely within the landscape. In this way, requirements for the conservation of the bat fauna could be effectively integrated in landscape planning. In general, the comprehensive analysis of the bat fauna data reveals new aspects of landscape, which are not shown by a mere habitat survey, or by data on other animal species. This therefore enhances the possibilities for the conservation and development of the landscape.

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