Urbanization is one of the main drivers of ecological change in the modern world. In most cases, species diversity in urban landscapes is lower than in natural ones; however, some groups of animals are able to exploit and benefit from urban habitat. Pipistrellus kuhlii s.l. is (P. k. lepidus according to recent taxonomic review), a common European urban bat, whose range has expanded on a wide scale in the last 40 years. Thought to originate in Central Asia, this species has extended its range throughout Eastern and Central and Europe (a distance of more than 2,500 km2) in part by using human settlements as a habitat. This study examines the ecological features of P. k. lepidus in wintertime in the Eastern part of Ukraine, where this species has been living for 20 years. Thirty-nine winter records of P. k. lepidus(1,301 individuals totally) were selected from the database of the Bat Rehabilitation Center of Feldman Ecopark, 19 of which were groups from 2 to 641 individuals. Pipistrellus k. lepidus was found in various types of structures, but most often in administrative buildings (school buildings - 69%). Records were usually obtained during renovation works (85%), and the roosting sites were cavities between the wooden planks of window frames and a wall (75%). The records were obtained in 26 settlements, from a village (0,293 kmand 252 people) to the biggest cities in the country (Kharkiv and Odessa). The sex ratio in winter aggregation in adults varied from 47% to 61% of females and for this-year individuals from 48% to 58%, respectively. The body mass at the end of the hibernation period (February/March) decreases for 17–20% compared to the beginning of the period (December). Adult females have bigger body size (body mass and forearm length) (p-value < 0.05). Our results showed that P. k. lepidus is capable of forming homogeneous, sedentary populations in all types of settlements in Ukraine for these twenty years. However, this choice of habitat means that the species faces a high mortality risk from humans during building renovation and insulation works or pest control actions.

Bats are volant and highly mobile mammals that could cover up to 2000 km seasonally (one-way migration). But the level of mobility among diff erent roosts sites in a breeding season, and among breeding areas and hibernation sites is poorly studied. With this communication, we aimed to present results of recaptures (51 cases with a distance of 0.5 km and more) of bats ringed in Kharkiv Region, Ukraine, from 2006 to 2018. Th e recaptures were obtained of three main study areas (NNP "Homilsha Forests" -17 cases, Izium District -5, Kharkiv City and surroundings -27) and at two other localities of the Kharkiv Region. One recapture was obtained in Lugansk Region. Th e recaptures were received for fi ve bat species (Nyctalus noctula-35, Myotis daubentonii-11, Eptesicus serotinus -1, Pipistrellus nathusii -1 and Pipistrellus pygmaeus -3). Th e maximum distances were obtained to diff erent species as follow N. noctula -209.7 km, M. daubentonii -24.8, E. serotinus -14.5 km, P. nathusii -1.1 km and P. pygmaeus -1.2 km. For the fi rst time, we confi rmed that N. noctula that were born in forested areas of Kharkiv City surroundings moved to the built-up area of the city for hibernation. It is the fi rst direct evidence of the existence of the resident population of this species in Ukraine.

Insectivorous bats provide important ecosystem services, especially by suppressing and controlling the insects’ biomass. To empirically quantify the amount of insects consumed by European vespertilionid bats per night, we estimated their ratio of dry mass of feces to mass of consumed insects. This study combines the results of feeding in captivity and the data obtained in field surveys; dry mass of feces was measured in both cases. In captivity, we analyzed the effect of species, age and sex of bats, species of insects consumed and the mass of food portion on the dry mass of feces. Using coefficients of the regression model, we estimated the amount of insects consumed by free-ranging bats based on dry mass of their feces. According to our estimates, on average, one individual of one of the largest European bat species, N. noctula, consumes 2.2 g (ranging from 0.5 to 8.5 g) of insects per one feeding night, while the smallest European bats of genus Pipistrellus consume 0.4 g (ranging from 0.1 to 1.3 g), further confirming the importance of insectivorous bats for ecosystem services. This publication offers the novel method for the estimation of insects’ biomass consumed by bats.

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Copulatory behaviours stand as cornerstones of sexual selection, yet they remain mysterious in many species, especially in bats. An extremely large penile erection with a heart-shape terminal swelling has been observed in the serotine bat (Eptesicus serotinus). The engorgement of the erectile tissues could take place after penetration to generate a copulatory lock. Alternatively, the erected penis, long and mobile, could be used to pass by the protective tail membrane to reach the vulva. In the latter scenario, the penis may however not be able to penetrate the vagina. In order to find out which of the two scenarios occurs, we investigated the morphology of female and male genitalia of E. serotinus. We found that the vagina is more than seven times shorter than the erected penis, supporting that the penis is used as a copulatory arm rather than an intromittent organ. We could confirm our hypothesis with direct observations of copulations. During mating, the male grasps the female in a dorsoventral position. The male probes the female’s ventral part with its erected penis until the penis is tightly pushed against the vulva. Afterward, the pair stops moving and can hold the position for several hours. In addition, the timing of copulations, which exhibits a peak in October, implies that visits to swarming sites throughout the year may serve other functions besides mating. This research reveals a novel copulatory behaviour that has not been previously documented in mammals and sheds light on the poorly understood area of bat reproduction.