Behavioral ecology of bats in urban and suburban areas: an eco-ethological approach to conservation

Human tolerant species of bats are an important constituent of the biodiversity, albeit-low, in urban and suburban ecosystems. They usually survive by taking refuge inside human artefacts and sometimes using urban green spaces as foraging areas, where they assist in regulating insect density thus providing an important ecosystem service to citizens. Their conservation is therefore particularly important also because of their status which is threatened throughout Europe. I studied the ecology of the shelters choice of both the group of species which roost in buildings and in other human artefacts in Italy: crevice dwelling bats and those that need larger volumes like attics or cellars. As a model species to study the latter group I chose a nursery colony of Rhinolophus ferrumequinum which during the spring-autumn period live in the Natural Park of Migliarino San Rossore Massaciuccoli. I monitored four different roosts that the colony can select throughout the year and I found that the internal microclimatic conditions (temperature and relative humidity) as well as the risk of predation influence significantly the choice by bats which can easily shift between their roosts in cases of necessity. To study the preferences of crevice dwelling bats I used the bat boxes, which are artificial roosts for bats. These shelters were placed by a large amount of citizen volunteers who monitored the colonization of their roosts throughout the year. Monitoring data were collected yearly and their analysis showed a similar trend to the other group of species. Bats choose their roost to better suit their termoregulatory needs and to avoid the risk of predation, selecting the roosts placed since more time. The study, which was conducted over more years, also showed that bats learn to use bat boxes over time, colonizing them earlier in the years subsequent the first year of occupation. I also studied more in depth how the internal temperature affects the choice of roosts in crevice dwelling bats and I found that these animals likely select the roost in order to save energy during the daily torpor. My results also showed a minor utilization of spring-autumn roosts during winter by some individuals both in crevice dwelling and in species which need large volumes. This may be related either to the urban heat-island effect or to a general climate change, at least in the strictly urban species. I also studied the emergence and pre-emergence behavior of a nursery colony of R. ferrumequinum throughout the year, also focusing on the reproductive period. The nightly emergence in bats is a tradeoff between the opportunity to prey and the risk of being a prey for diurnal raptorial birds. The onset of such behaviour is regulated by an endogenous circadian rhythm which is adjusted by various ecological factors. I showed that the onset of the emergence, as well as its distribution of intensity, is influenced by the temperature and by the evening light intensity which facilitate the evening arousal and decrease the predation risk, respectively. The onset of the pre-emergence light-sampling behavior is also anticipated by the presence of pups which increase the trophic necessities of lactating females. The duration of the nightly emergence is although mainly influenced by the presence of juveniles which, leaving later than adults to avoid predation, cause a longer emergence. The distribution of about 50000 bat boxes over five years through the “BAT BOX: be a bat’s friend” project also allowed to involve people directly in a conservation programme entirely focused on bats. To raise people interest and awareness I properly talked, through public meetings, interviews and brochures, about the ecosystem services that bats perform. In particular I focused on the control of insects, thus contributing to change the originally bad attitude toward bats. Through the project I succeeded in positively influencing the behavior of people, making bats a flagship species for the sustainable control of harmful insects.