Bats show pronounced and often-adverse reactions to artificial illumination at night (ALAN) when commuting, roosting or foraging. ALAN also affects bat drinking activity, at least when lighting occurs over short intervals. We tested whether continuous illumination of drinking sites over 4-h periods would lead bats to tolerate ALAN and resume drinking in the course of the night. We conducted our experiments in forest (Italy) and desert (Israel) sites to test whether in the latter habitat, where water is scarce, a greater motivation to drink might lead to less adverse bat reactions. We recorded 6853 drinking buzzes and 1647 feeding buzzes from 17 species and one species group. In the forest sites, species that hunt in open spaces or along forest edges showed little (P. pipistrellus and H. savii) or no (P. kuhlii and N. leisleri) drinking activity decrease, while those associated with forest interiors (Barbastella barbastellus, Plecotus auritus and bats in the genus Myotis) exhibited a strong negative response. In the desert sites, all studied species reduced drinking activity, yet in the desert populations of P. kuhlii we recorded stronger adverse reactions only far from human settlements. The harsh reactions that the desert bat species showed towards ALAN rule out any effect of a greater motivation to drink. Illumination had no effect on foraging by most species, except in the forest sites, where Pipistrellus kuhlii and Nyctalus leisleri increased foraging when the light was on, and in the desert sites, where Hypsugo bodenheimeri decreased foraging in such situations. The progressive human encroachment that is taking place in many world regions on both forests and especially deserts, where few sites for drinking are available, may jeopardize bat populations also through increased exposure to ALAN.
Understanding how species respond to climate change is key to informing vulnerability assessments and designing effective conservation strategies, yet research efforts on wildlife responses to climate change fail to deliver a representative overview due to inherent biases. Bats are a species-rich, globally distributed group of organisms that are thought to be particularly sensitive to the effects of climate change because of their high surface-to-volume ratios and low reproductive rates. We systematically reviewed the literature on bat responses to climate change to provide an overview of the current state of knowledge, identify research gaps and biases and highlight future research needs. We found that studies are geographically biased towards Europe, North America and Australia, and temperate and Mediterranean biomes, thus missing a substantial proportion of bat diversity and thermal responses. Less than half of the published studies provide
1. During their seasonal migration, birds stage in areas comprising stopover sites of varying quality. Given that migrating birds have a limited information about their environment, they may land at a low-quality stopover site in which their fuel deposition rate (FDR) is low. Birds landing at such sites should decide either to extend their stopover duration or to quickly depart in search for a better site. These decisions, however, strongly depend on their body condition upon landing. 2. To understand the decision-making process of passerines within a stopover area, comprising stopover sites of varying quality, prior to the crossing of a large ecological barrier, we constructed a state-dependent habitat selection model. The model assumes that even if migrating birds have an expectation of encountered area quality, they cannot control for their initial landing site. Once landing, movement between low-and high-quality stopover sites will occur only if the body condition of these birds is high to the extent that they can entail the energetic cost of movement. Birds in the model aim to maximize their fuel load at the end of the stopover period, to suffice for successfully crossing a large ecological barrier.3. The model is based on empirical data on autumn migrating Blackcaps Sylvia atricapilla, collected at two important stopover sites in the Negev desert of Israel.Migrating passerines staging at these two sites differ in their FDR and body condition. The model shows that the optimal behaviour when arriving at a low-quality stopover site is to abandon it quickly. However, as lean individuals cannot entail the costs of searching for an alternative site, they have no other choice but to stay there even if their chances to successfully cross the Sahara Desert ahead are low. 4. Our model can be applied to other ecological systems. Proper use of this model may allow good assessment of stopover site quality, as indicated by the bird's FDR, regardless of specific site characteristics. Hence, it can help applying targeted management decisions regarding the maintenance of stopover sites or establishment of new ones.
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