A multimethod approach to the study of bats distribution and ecology in catalonia

Resumen

Overview and objectives Approximately 1,200 species of bats exist on Earth (Linzey, 2001). Being the only true flying mammals, their mobility and longevity combine to make them well suited as indicators of environmental conditions (Fenton, 1997). Moreover, because bats are heavily affected by anthropogenic habitat change, their status has received increasing attention in recent years at international level, reflecting the importance of their role in biodiversity and ecosystem functioning (Anthony and Kunz, 1977; Hutson, Mickleburgh and Racey 2001) even, for example, in semi-natural agricultural ecosystems, where they play a major role as pest controllers (Whitaker, 1995; Cleveland et al., 2006). In Europe, bats are the most speciose mammal group and possibly the most threatened (Hutson, Mickleburgh and Racey 2001). Implementing conservation strategies requires deep knowledge of bat ecology and behaviour. Furthermore, bats' ecological requirements may vary according to geographical region and so it may be incorrect to apply automatically knowledge acquired elsewhere even if the same species or assemblages are involved (Russo and Jones, 2003). This doctoral work focuses on testing methodologies to study bats in order to know more about habitat use and the conservation ecology of bats in Catalonia, a major region of the Iberian Peninsula. Catalonia (north-east Iberian Peninsula) covers 32,000 km² and is characterised by rich landscape heterogeneity, with a wide altitude range (0 to 3,143 m a.s.l.). Its rich biodiversity has to survive in face of the enormous pressure exerted by a human population of over seven million people. The first studies of bats in Catalonia date back to the early 1920s (Aguilar-Amat, 1910, 1916, 1920, 1921, 1924), discontinued until the 1950s (Balcells 1954, 1961, 1964, 1965) until 1980s when new research began to produce a high number of studies (Carol et al., 1983; Arrizabalaga and Montagud, 1984; Serra-Cobo, 1987, 1990; Serra-Cobo et al., 1988, 2000a, 2000b, 2009; Ibáñez et al., 1992; Palomo and Gisbert, 2002; Flaquer et al., 2004; Palomo et al., 2007). All these studies are basically focused in bat distribution. In Europe, most sparsely used methods to inventory bat communities are: bat detectors, mist nets and roost surveys. In order to reduce bias in species detection, I decided to test all these methods as well as bat boxes and radiotracking as a means to improve the knowledge of Catalan bat species. During the last decade, bat detectors technology has improved and researchers are feeling more confident to use it in their surveys. This doctoral work also tries to find out bat detectors possibilities as an inventory technique considering that just objective and quantitative identification methods are recommended; otherwise, surveys may be seriously misinterpreted (Jones et al., 2000). Russo and Jones (2002) have also pointed out that when bats are identified by their echolocation calls it is important to use a discriminatory method that makes it possible to quantify the degree to which the identification is correct. As well, it is much more difficult to compare statistically species identification based on acoustic devices made by different field workers (Barclay, 1999; White and Gehrt, 2001). Finally, geographical differences in calls may also mean that reference calls obtained from one population are of limited use in a different area (Swier, 2003). I here present a work based on a long term roost surveys. On the basis of their breeding roost preferences Catalan bat species were grouped into 3 guilds: caves or/and buildings roosting bats, rock or man-made structure crevices-roosting bats and tree roosting-bats (Flaquer et al., 2007b). In Europe, populations of cave-roosting bats are decreasing due to 1) speleotourism, 2) the loss of old buildings and 3) the closure of mine entrances and vandalism (Mitchell-Jones, 2007). The most endangered cave-dwelling Catalan bat is the Long-fingered bat Myotis capaccinii, a species that also needs well-preserved rivers as foraging areas (Almenar et al., 2006; Biscardi et al., 2007). In an even worse situation is the Mehelyi's Horseshoe bat Rhinolophus mehelyi, of which there is no recent evidence of its presence (Flaquer et al., 2004; Serra-Cobo et al., 2009). According to Russo et al., (2005), the reduction of foraging habitats (i.e. pastures) may well be a major threat to this species. The vandalism of caves used as bat roosts, speleotourism and the closure of mine entrances may also be a major threat to this bat. Other than the Lesser Horseshoe bat Rhinolophus hipposideros and the Greater Horseshoe bat Rhinolophus ferrumequinum, all cave-roosting species are vulnerable in Catalonia: both these species, though, are frequent in Catalonia (Flaquer et al., 2004; Serra-Cobo et al., 2009) and their success has probably been achieved by adapting to man-made structures such as bunkers, houses, cellars and castles. As well, the former has benefited from the expansion of forest cover in Catalonia (Botadina et al., 2002). During field work I have had serious doubts about how to sample colonies of forest-roosting bats (i.e. Myotis bechsteinii; Myotis alcathoe, Plecouts auritus, Barbastella barbastellus) very rare in Catalonia (Flaquer et al., 2004). However, if we only consider surveys from well-preserved forested areas in the Pyrenees, forest bats are in fact the commonest species (Flaquer et al., 2008). Thus, I have hypothesized that a combination of different methods used in Catalonia may also work in the study of forest bats and lack of them could be considered as a result of the type of forest management politics. This species breeds in preserved forests, where probably find better roost options (Russo et al., 2004). Contrary, Catalonian forests have been submitted to continuous cuttings of biggest trees (from 35-45 cm of diameter) so main forests lack on big old trees (Camprodon 2003; Flaquer et al., 2007a). Tough, bat boxes inspection is a time consuming method to inventory bats; I decided to test this method during my approach to study Catalan bats. Moreover, following Biscardi et al., (2007) I radiotracked bats looking for much more robustly habitat preference patterns than using methods with a coarse spatial resolution (i.e. mist-netting or acoustic surveys). Main objectives and Thesis structure The conservation of Catalan bat populations requires a sound background in ecology and behaviour. The aim of this thesis is to take this first step towards the development of an effective Catalan Bat Conservation and Management Programme. Specifically, thus, I have pursued the following objectives: 1)To test different methods of studying bats in order to identify the most effective methods for future survey work 2)To select poorly known species of special conservation interest and provide a detailed analysis of habitat selection 3)To contribute to developing conservation guidelines These objectives are pursued in all sections of this thesis, which is structured in five chapters. Chapter 1 deals with the performance of the methods tested during inventory work, while chapters 2 to 5 focus on specific habitat selection studies dealing with three poorly known species, for which different methods (bat box inspection and radiotracking) were employed. As a result of intensive surveying efforts (from 1999 to 2005) the number of bats recorded in Catalonia has increased notably (Flaquer et al., 2004) and the advantages and disadvantages of each method used has been evaluated (Flaquer et al., 2007b; Chapter 1). Bat boxes were found to be useful for studying and conserving soprano pipistrelle (Pipistrellus pygmaeus) breeding colonies in wetlands (Flaquer et al., 2006, Chapter 2), as well as those of Nathusius' pipistrelle Pipistrellus nathusii (Flaquer et al., 2005, Chapter 3). Given the relevance of new techniques in bat studies, I decided to go a step further and (for the first time in Catalonia) I studied bat habitats by means of radiotracking (Chapters 4 and 5). 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