The gastrointestinal tract of animals is adapted to their primary source of food to optimize resource use and energy intake. Temperate bat species mainly feed on arthropods. These contain the energy-rich carbohydrate chitin, which is indigestible for the endogenous enzymes of a typical mammalian gastrointestinal tract. However, the gastrointestinal tract of bat species should be adapted to their diet and be able to digest chitin. We hypothesized that (i) European vespertilionid bat species have the digestive enzyme chitinase and that (ii) the chitinolytic activity is located in the intestine, as has been found for North American bat species. The gastrointestinal tracts of seven bat species (Pipistrellus pipistrellus, Plecotus auritus, Myotis bechsteinii, Myotis nattereri, Myotis daubentonii, Myotis myotis, and Nyctalus leisleri) were tested for chitinolytic activity by diffusion assay. Gastrointestinal tracts of P. pipistrellus, P. auritus, M. nattereri, M. myotis, and N. leisleri were examined for acidic mammalian chitinase by western blot analysis. Tissue sections of the gastrointestinal tract of P. pipistrellus were immunohistochemically analyzed to locate the acidic mammalian chitinase. Chitinolytic activity was detected in the stomachs of all bat species. Western blot analysis confirmed the acidic mammalian chitinase in stomach samples. Immunohistochemistry of the P. pipistrellus gastrointestinal tract indicated that acidic mammalian chitinase is located in the stomach chief cells at the base of the gastric glands. In conclusion, European vespertilionid bat species have acidic mammalian chitinase that is produced in the gastric glands of the stomach. Therefore, the gastrointestinal tracts of insectivorous bat species evolved an enzymatic adaptation to their diet.

Like other small terrestrial mammals, bats have a high mass‐specific energetic demand because of the fact that they have an unfavorable surface area to volume ratio. Furthermore, bats have a very energy‐expensive mode of locomotion: flight. This high energetic demand has to be covered by food intake. The retention time of the digestive tract is one factor affecting the energy intake of bat species. Factors like energy demand, gut volume and dietary specialization influence retention time in mammals. However, maximum retention time for only Myotis myotis and transit time only for M. lucifugus, Nyctophilius gloudi and Nyctalus noctula is known. This study investigated the maximum retention times and transit times of 10 Central European bat species. It was hypothesized that the level of specialization of the digestive tract, energy‐demanding processes and intestine length would affect the retention time of bats. Fluorescence‐marked mealworms Tenebrio molitor were used to measure the time between the first ingested mealworm and the first appearance of the marker or the last fluorescing feces, respectively. For the first time, the retention time of 10 insectivorous bat species was measured to determine interspecific differences. Additionally, we measured the retention time of post‐lactating female and spermatogenically active male Pipistrellus pipistrellus to determine intraspecific differences. The retention time of bats differed significantly between species and is probably influenced by the level of specialization of the digestive tract. High‐level specialization of the digestive tract resulted in short retention times. Furthermore, significant intraspecific differences between post‐lactating and spermatogenically active individuals of P. pipistrellus showed that the retention time within a single species might be influenced by energy‐demanding processes (e.g. reproduction).

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This study applied the analysis of stable isotope ratios as a minimally-invasive tool to estimate the diet of Cricetus cricetus for the first time. We took hair and food samples of three different populations of C. cricetus and analyzed stable carbon and nitrogen ratios. The stable isotope ratios in hamster hairs differed significantly within and between populations according to different sampling seasons and animal ages. Additionally, the isotopic signatures of potential food samples differed between sampling sites and food categories. The isotopic mixing models illustrated that diet composition varied with season and food availability. During the summer season hamsters living in agricultural areas mainly fed on green and ripe crop. In contrast to this, during the winter season ripe crop was the main food component for hamsters in agricultural areas while hamsters living in urban areas fed almost exclusively on nuts. These are, despite a wide variety of available food sources, most suitable for hoarding in the burrow. We conclude that stable isotope analysis of hamster hairs is an appropriate minimal-invasive method to investigate correlations between available and consumed food sources throughout the overall distribution of this species.