The parasite load of seven European bat species (Myotis daubentonii, Myotis emarginatus, Myotis myotis, Myotis mystacinus, Myotis nattereri, Nyctalus noctula, Pipistrellus pipistrellus) was compared and tested to see if there was a relationship between high parasite load and poor body condition in bats. Considerable variations of the parasite load between host species, ages and sexes were found, which can be attributed to roosting conditions and behavioural differences of the bats. Overall, male bats had the fewest parasites. Very different parasite population densities were found in different years, and also at the same time at different sites. A generally high parasite load during the nursing season was not observed. There was no strong trend of increasing parasite load in bats with decreasing condition. If weak bats had more parasites than other individuals, the high number of parasites seemed to be a symptom and not the direct cause of the bad condition.

Data are presented on a bat assemblage captured among 10 water holes in Colorado over 5 years. The assemblage consists of Myotis ciliolabrum, M. evotis, M. lucifugus, M. thysanodes, M. volans, Eptesicus fuscus, Lasiurus cinereus, Lasionycteris noctivagans and Corynorhinus townsendii. Results show that reproductive females and juveniles are captured in higher frequencies at water holes containing higher water hardness and that water hardness correlates highly significantly with dissolved calcium content. Also presented are laboratory test data on the stomach volume of Eptesicus fuscus that provide a model for understanding the effect of dissolved calcium content in water as a significant resource. These data indicate that water holes provide supplemental sources of calcium for bats not provided by diet.