Aspects of ecomorphology in the five European horseshoe bats (Chiroptera: Rhinolophidae) in the area of sympatry der Fakultät für Biologie der EBERHARD KARLS UNIVERSITÄT TÜBINGEN zur Erlangung des Grades eines Doktors der Naturwissenschaften von Christian Dietz aus Tübingen vorgelegte Dissertation 2007 Tag der mündlichen Prüfung: 14.11.2007 Dekan: Prof. Dr. H. Mallot 1. Berichterstatter: Prof. Dr. H.-U. Schnitzler 2. Berichterstatter: PD Dr. B.M. Siemers Table of contents 3 Table of contents Structure of this thesis................................................................................................................ 8 Publication of the results............................................................................................................ 9 Author information and contributions from others .................................................................... 9 References ................................................................................................................................ 10 Chapter 1 - Identification key to the horseshoe bats of Europe ............................................... 15 Chapter 2 - Age classification and assessment of reproductive condition............................... 33 Chapter 3 - Effects of forearm bands on horseshoe bats.......................................................... 62 Chapter 4 - Movements of horseshoe bats in northern Bulgaria.............................................. 84 Chapter 5 - Growth of horseshoe bats and the influence of climate ...................................... 110 Chapter 6 - Wing measurement variations in the five European horseshoe bat species........ 138 Chapter 7 - Comparative wing morphology of five sympatric horseshoe bat species........... 170 Zusammenfassung.................................................................................................................. 220 Veröffentlichung und Eigenanteil .......................................................................................... 233 Danksagung............................................................................................................................ 235 Lebenslauf .............................................................................................................................. 237 General introduction 4 General introduction The study of mechanisms enabling species to coexist in sympatry is one of the most challenging topics in ecology. Competition avoidance and resource partitioning are of special interest in species exploiting similar resources. Groups of such species depending on similar resources are guilds, defined as a community of animals showing a considerable overlap in their ecology mainly due to a similar way of exploiting the same class of environmental resources, e.g. the members may use similar feeding or prey capture strategies (Root 1967). According to the competition exclusion principle, similar species evolve different ecological niches to reduce or avoid competition (Hardin 1960; Schoener 1974; Wiens 1977). Separation can be achieved by several mechanisms such as character displacement (Brown and Wilson 1956); selection of different habitats, prey types, foraging times and foraging styles (e.g., Aldridge 1986; Jones et al. 1993); morphological variation (Bogdanowicz et al. 1999; Findley et al. 1972; Van Valen 1965); and differences in sensory ecology (Kingston et al. 2000; Siemers and Swift 2006). As animal communities are rarely structured by the limitation of a single resource but mostly by a combination of many resources with a changing importance in different stages of an individual’s life, an all-encompassing study on community-level coexistence would be a very demanding task. In addition, resource availability (e.g., prey abundance) may change a lot within the course of a year or may differ between years and thus might be unlimited at a certain time. To unravel all possible causes and mechanisms of coexistence unfortunately is much beyond the possibilities of a relatively short-termed research project like a PhD-project. Within my project I focused on the flight-ecomorphology as one possible mechanism structuring a guild of sympatric bat species. The five species under study belong to the family Rhinolophidae and can be united in a single guild of ‘aerial insectivore narrow space flutter- detecting foragers’ (Schnitzler and Kalko 1998, 2001; Schnitzler et al. 2003) on the basis of General introduction 5 the unique combination of echolocation call design, wing morphology, foraging style and prey consumed. These 5 European horseshoe bat species (Rhinolophus hipposideros, R. mehelyi, R. blasii, R. euryale and R. ferrumequinum) are closely-related members of a single genus (Guillén et al. 2003) and have extensive overlap in their distribution in southeastern Europe (Mitchell-Jones et al. 1999), where they occur in sympatry on the Balkan Peninsula and the eastern Mediterranean. All of them produce long duration constant-frequency echolocation calls with a maximum energy concentrated in the 2nd harmonic (Griffin and Simmons 1974; Heller and von Helversen 1989; Jones and Rayner 1989; Möhres 1953; Russo et al. 2001; Siemers et al. 2005). Horseshoe bats use frequency and amplitude shifts modulated onto the echoes of their constant-frequency calls by the wing beats of insects as a means of detecting prey (Schnitzler 1983). All European horseshoe bats are similar in several morphological respects, including short and broad wings with a large wing area giving low wing loading, aspect ratio and tip shape index (Findley et al. 1972; Norberg 1987; Norberg and Rayner 1987). However, the European species differ in size and body mass: The average body mass and forearm length of the lesser horseshoe bat (R. hipposideros) are 6-7 g and 37-42 mm respectively, those of the greater horseshoe bat (R. ferrumequinum) 20-26 g and 54-61 mm, and those of the 3 medium- sized species (R. mehelyi, R. blasii and R. euryale) are quite similar (9-14 g and 42-54 mm, respectively - Schober and Grimmberger 1998; Dietz et al. 2007b). All 5 species catch prey by “flycatching” from a perch or during patrolling flights close to a cluttered background, and at least some species may also take prey from the ground (Bontadina et al. 2002; Jones and Rayner 1989; Russo et al. 2002, Siemers & Ivanova 2004). With the exception of the lesser horseshoe bat (R. hipposideros), these 5 horseshoe bat species prey predominately on nocturnal moths (Beck et al. 1989, 1997; Goiti et al. 2004; Valenciuc 1971). The lesser horseshoe bat (R. hipposideros) is distributed over most of southern and central Europe and has the northernmost limit of distribution of all rhinolophids in Europe, reaching Ireland, the General introduction 6 Netherlands and Poland (Mitchell-Jones et al. 1999). The species prefers to roost in buildings, but colonies in the south are also found in caves (Dietz et al. 2007b). The species preys mainly on small Diptera, Lepidoptera and other small insects, predominately in or close to forests (Beck et al. 1989; Bontadina et al. 2002; Jones and Rayner 1989). The greater horseshoe bat (R. ferrumequinum) is found in southern and central Europe as far north as southern England and Wales, the Netherlands and Poland (Mitchell-Jones et al. 1999). Breeding colonies in the north are mainly in buildings, in the south predominately in underground roosts (Dietz et al. 2007b). These bats forage in a wide variety of habitats from open meadows to parks and woodlands, where they prey mainly on coprophagous beetles and moths (Beck et al. 1997; Bontadina et al. 1995, 1997; Jones and Rayner 1989; Jones et al. 1995). The ecologies of the 3 medium-sized species are less well known. Their distribution in Europe is confined to the area around the Mediterranean. The Mediterranean horseshoe bat (R. euryale) has the widest distribution, extending north to central France, Italy, Slovakia and Romania; Mehely’s horseshoe bat (R. mehelyi) is found in southern and central Iberia, southern France, Sardinia, Sicily, Greece and in the Balkans north to Romania; Blasius’ horseshoe bat (R. blasii) is restricted to southeastern Europe from the Adriatic coast over the Balkans to Greece and Romania (Mitchell-Jones et al. 1999). All 3 species roost mainly in caves and other underground galleries (Dietz et al. 2007b) and prey predominately on moths (Goiti et al. 2004; Valenciuc 1971; Whitaker and Black 1976). R. euryale forages mainly in forests, while R. mehelyi prefers to forage in less densely vegetated habitats of a savannah- type (Russo et al. 2002, 2005). Habitat preferences of R. blasii remain unknown (Siemers and Ivanova 2004; Dietz et al. 2007b). One of the most important mechanisms of character displacement is morphological variation (Bogdanowicz et al. 1999; Findley et al. 1972; Van Valen 1965). Especially in bats the morphology of the wings can be regarded as being highly adaptive. Beside its sensory ability to detect and recognize prey (Siemers and Schnitzler 2004), an insectivorous bat’s ability to General introduction 7 use its environment depends largely on its ability to maneuver through habitats (Norberg and Rayner 1987) and on its maneuverability when foraging for prey (Fenton 1990; Findley et al. 1972; Vaughan 1959). Changes in morphology result in differences in flight performance (Adams 1996; Aldridge 1986; Findley and Black 1983; Norberg 1981) which directly affect habitat use (Aldridge and Rautenbach 1987; Brigham et al. 1997; Jacobs 1996, 1999; Norberg