Dietary niche partitioning is postulated to play a major role for the stable coexistence of species within a community, particularly among cryptic species. Molecular markers have recently revealed the existence of a new cryptic species of long-eared bat, Plecotus macrobullaris, in the European Alps. We studied trophic niches as well as seasonal and regional variations of diet in eight colonies of the three Plecotus species occurring in Switzerland. Faeces were collected monthly from individuals returning to roost after foraging. Twenty-one arthropod categories were recognized from the faeces. All three species fed predominantly on Lepidoptera, which made up 41%, 87% and 88% (means across colonies) of the diet composition of P. auritus, P. macrobullaris and P. austriacus, respectively. The occurrence of numerous fragments of both diurnal and flightless insects in the diet of P. auritus (but rarely in the diet of the other two species) indicates that this species mostly gleans prey from substrates. P. austriacus and P. macrobullaris are more typical aerial feeders. The latter two species have narrow trophic niches, whilst P. auritus has a much broader diet. Comparison of intraspecific and interspecific niche overlaps in P. auritus and P. macrobullaris in sympatry suggests dietary niche partitioning between these two species. In contrast, the high similarity of the trophic niches of P. austriacus and P. macrobullaris, associated with a typical parapatric distribution, indicates competitive exclusion. The best conservation measures are preservation and restoration of habitats offering a high abundance of moths, the major prey of the three Plecotus species.

Summary 1.Recognizing the factor(s) that caused a demographic crash is a prerequisite to the development of a tailored population restoration plan. While habitat destruction leaves little scope for population persistence, cryptic habitat deterioration (for example through reduction of food resources) may similarly render an area totally inhospitable, while it still appears to have a suitable habitat configuration. 2. Most European bat species have undergone dramatic declines over the past decades. Once among the most widespread and abundant bat species of Central Europe, the lesser horseshoe bat, Rhinolophus hipposideros (Bechstein 1800), is today extinct in many regions. Although changes in the agricultural landscape have been suggested as the major cause of decline, recent studies have shown that this bat forages almost exclusively in woodland, a habitat that has increased in area across continental Europe over the past decades. This suggests that habitat eradication per se is unlikely to be the main cause of decline. But could cryptic habitat deterioration play a harmful role? 3. We looked at the abundance of insect prey in woodland in the vicinity of colonial roosts with diverging demographic status (extinct, declining or recovering populations), both in the Swiss lowlands (Swiss Plateau) and in the Alps. We predicted that population size correlates positively with prey abundance. 4. Diet composition mirrored local insect prey abundance, confirming an opportunistic foraging strategy. Prey abundance showed marked seasonal variation, but did not differ between sites harbouring extinct, declining or recovering populations. There was also no difference in food abundance between extinct populations in the lowlands and recovering populations in the Alps. 5. Synthesis and applications. Cryptic habitat deterioration through a reduction in prey abundance is unlikely to preclude recolonization of abandoned areas by presently recovering populations. However, sufficient areas of natural forest should be preserved or created around potential nursery roosts. Moreover, connectivity between forest patches must be ensured (by creation of hedges and tree lines) to prevent any spatial gap in recolonization within semi-open agricultural landscapes. Other threatened European forest bats may also benefit from these measures.

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Nutritional habits of the Lesser Horseshoe bat Rhinolophus hipposideros (Bechstein, 1800) (Mammalia, Chiroptera). -Analysing the excrements and bitten-off food remains of R. hipposideros in Switzerland allowed its nutritional habits to be identified, both in terms of quality and quantity. R. hipposideros preferably feeds on Diptera, Lepidoptera and Neuroptera, special importance being attributed to Sy/vicola punctatus as well as to representatives of Tipulidae and Hemerobiidae.Many of these soft, slow and low-flying insects are captured in abundantly structured hedges, woods and their outskirts near to water and point to a flycatcher hunting strategy of R. hipposideros. EINLEITUNGMethodische Griinde limitieren die direkte Beobachtung jagender Fledermause im Feld. Es fehlen daher wichtige Informationen über die spezifischen Jagdhabitate, Jagdstrategien und Nahrungsgrundlagen der einheimischen Fledermausarten. Von der Kleinen Hufeisennase (Rhinolophus hipposideros), eine der am stärksten bedrohten Fledermaus-' Die vorliegende Arbeit entstand im Rahmen eines Forschungsprogramms des 3. Autors, das vom Schweizerischen Nationalfonds unterstützt wurde.

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