Rain increases the energy cost of bat flight

Similar to insects, birds and pterosaurs, bats have evolved powered flight. But in contrast to other flying taxa, only bats are furry. Here, we asked whether flight is impaired when bat pelage and wing membranes get wet. We studied the metabolism of short flights in Carollia sowelli, a bat that is exposed to heavy and frequent rainfall in neotropical rainforests. We expected bats to encounter higher thermoregulatory costs, or to suffer from lowered aerodynamic properties when pelage and wing membranes catch moisture. Therefore, we predicted that wet bats face higher flight costs than dry ones. We quantified the flight metabolism in three treatments: dry bats, wet bats and no rain, wet bats and rain. Dry bats showed metabolic rates predicted by allometry. However, flight metabolism increased twofold when bats were wet, or when they were additionally exposed to rain. We conclude that bats may not avoid rain only because of sensory constraints imposed by raindrops on echolocation, but also because of energetic constraints

Improving attitudes and knowledge in a citizen science project about urban bat ecology

In order to deal with the current, dramatic decline in biodiversity, the public at large needs to be aware of and participate in biodiversity research activities. One way to do this is citizen science projects, in which researchers collaborate with volunteering citizens in scientific research. However, it remains unclear whether engaging in such projects has an impact on the learning outcomes of volunteers. Previous research has so far presented mixed results on the improvement of citizens’ attitudes and knowledge, mostly because such research has focused only on single aspects of citizen science projects in case studies. To address these limitations, we investigated the impact of an urban bat ecology project on citizens’ attitudes and knowledge about bats, and on their engagement with citizen science. We also examined whether the degree of citizen participation (i.e., collecting data vs. collecting and analyzing data) had an influence on the outcomes. We conducted four field studies and used a survey-based, experimental, pre-/post-measurement design. To vary the degree of participation, we assessed the post measurement in one group directly after data collection, whereas, in a second group, we assessed it after data collection and analysis, at the end of the project. Across all studies, the results demonstrated that citizens’ content knowledge of urban bat ecology increased, and their attitudes toward bats and toward their engagement in citizen science improved during their participation. Citizens’ degrees of participation did not influence these outcomes. Thus, our research illustrates that citizen science can increase awareness of urban bat conservation, independently of citizens’ degree of participation. We discuss the implications of our findings for the citizen science community. © 2022 by the author(s)

Establishing a Large-Scale Field Experiment to Assess the Effects of Artificial Light at Night on Species and Food Webs

Artificial light at night (ALAN) is one of the most obvious hallmarks of human presence in an ecosystem. The rapidly increasing use of artificial light has fundamentally transformed nightscapes throughout most of the globe, although little is known about how ALAN impacts the biodiversity and food webs of illuminated ecosystems. We developed a large-scale experimental infrastructure to study the effects of ALAN on a light-naïve, natural riparian (i.e., terrestrial-aquatic) ecosystem. Twelve street lights (20 m apart) arranged in three rows parallel to an agricultural drainage ditch were installed on each of two sites located in a grassland ecosystem in northern Germany. A range of biotic, abiotic, and photometric data are collected regularly to study the short- and long-term effects of ALAN on behavior, species interactions, physiology, and species composition of communities. Here we describe the infrastructure setup and data collection methods, and characterize the study area including photometric measurements. None of the measured parameters differed significantly between sites in the period before illumination. Results of one short-term experiment, carried out with one site illuminated and the other acting as a control, demonstrate the attraction of ALAN by the immense and immediate increase of insect catches at the lit street lights. The experimental setup provides a unique platform for carrying out interdisciplinary research on sustainable lighting

Urbanisation generates multiple trait syndromes for terrestrial animal taxa worldwide

Cities can host significant biological diversity. Yet, urbanisation leads to the loss of habitats, species, and functional groups. Understanding how multiple taxa respond to urbanisation globally is essential to promote and conserve biodiversity in cities. Using a dataset encompassing six terrestrial faunal taxa (amphibians, bats, bees, birds, carabid beetles and reptiles) across 379 cities on 6 continents, we show that urbanisation produces taxon-specific changes in trait composition, with traits related to reproductive strategy showing the strongest response. Our findings suggest that urbanisation results in four trait syndromes (mobile generalists, site specialists, central place foragers, and mobile specialists), with resources associated with reproduction and diet likely driving patterns in traits associated with mobility and body size. Functional diversity measures showed varied responses, leading to shifts in trait space likely driven by critical resource distribution and abundance, and taxon-specific trait syndromes. Maximising opportunities to support taxa with different urban trait syndromes should be pivotal in conservation and management programmes within and among cities. This will reduce the likelihood of biotic homogenisation and helps ensure that urban environments have the capacity to respond to future challenges. These actions are critical to reframe the role of cities in global biodiversity loss.info:eu-repo/semantics/publishedVersio

Künstliches Licht beeinflusst Fledermäuse unterschiedlicher Klimazonen und Ernährungstypen

Artificial light at night, in particular street lighting, is rapidly increasing globally and sprawls into formerly pristine areas. Worryingly, it can have detrimental effects on wildlife and eventually on biodiversity and ecosystem functioning. Therefore, artificial light is considered a pollutant changing the natural light-dark regime. Light pollution particularly impairs bats, the second most diverse mammal taxon. Bats have evolved traits well- adapted for nocturnal activity but which make them vulnerable to the prevailing high levels of artificial light at night. Indeed, over the past decades an increasing number of studies has demonstrated deleterious effects of artificial light on bats: it delays emergence of bats and reduces the number of emerging individuals, affects their commuting and foraging behaviour, interferes with navigation and slows down juvenile growth. In chapter 1 I review the existing literature, summarising the physiological and behavioural consequences that artificial light has for bats. I discuss the correlation between phototropism of insects and activity of light-tolerant bats and expound upon reasons for why and how this relation is very different for light-averse species. I then widen the scope to cascading effects at the ecosystem level. Finally, I suggest mitigation measures and conclude by pointing out remaining questions. A key finding of chapter 1 is that, to date, most studies have focused on insectivorous species in the temperate climate zone, although bat diversity is much higher in tropical regions. Tropical bats occupy central positions in the ecosystem and provide key ecosystem services. For instance, nectarivorous and frugivorous bats pollinate flowers and disperse seeds of numerous ecologically and economically important plants. To test how street lighting affects the foraging behaviour of frugivorous bats, I carried out experiments in both the field and a flight room using Carollia sowelli (chapter 2). Carollia sowelli is an abundant bat species in many Neotropical regions and constitutes a crucial seed disperser of pioneer plants. In chapter 2 I demonstrate that C. sowelli avoids lit areas in both space and time; specifically, it harvested less fruits in the vicinity of lit street lights, compared with unlit control lights. It stands to reason that if reduced harvesting translates into reduced seed dispersal, artificial light not only deteriorates food availability for light-averse bats, but could have far-reaching consequences for forest regeneration and compromise ecosystem functioning in Neotropical regions. Similarly, several insectivorous bats also reduce commuting and foraging when their habitat becomes lit. Other insectivorous species, however, exploit insect aggregations around street lights and reduce foraging efforts in that way. Thus, street lights can change local bat species composition and affect inter-specific competition. Yet, the impact of street lights differs between light types and strongly depends on their spectral signature. Across Europe and many non-European countries conventional mercury vapour (MV) street lights and other inefficient illuminants are being phased out and a widespread replacement by light- emitting diodes (LEDs) is expected. This change-over will tremendously alter the wavelengths spectrum of lightscapes at night. From a conservation perspective it is thus crucial to understand how modern LEDs differ from conventional illuminants concerning their impacts on wildlife. In order to predict the consequences of the anticipated changeover on urban bats, I conducted a large-scale field experiment across Germany where I compared bat activity at municipal MV street lamps that were replaced by LEDs with control lamps that remained with MV illuminants throughout the study. In chapter 3, I show that Pipistrellus pipistrellus, the most abundant species at my study sites, decreases its activity by 45% at LEDs compared with MV lights, probably in response to a reduction in insect numbers. In contrast, generally light- averse Myotis spp. increase their activity 4.5-fold when MV street lights are replaced by LEDs. These findings suggest that the transition from conventional MV lights to LEDs decreases the anthropogenic impact on bats in urban habitats. In the short-term, however, some species might suffer from a reduced foraging efficiency at LEDs. In conclusion, chapter 1 through 3 of my doctoral thesis demonstrate that the effects of artificial light are not restricted to insectivorous bats, but are also relevant for fruit-eating species. Further, my findings show that illuminants differ concerning their impact on bats and suggest that the negative effects of artificial light can be mitigated to some extent by replacing conventional illuminants with modern, less pernicious light types.Künstliches Licht, insbesondere Straßenbeleuchtung, wird weltweit in schnell zunehmendem Maße genutzt und dringt in vormals unberührte Gegenden vor. Besorgniserregend ist dabei, dass es Wildtiere beeinträchtigen und sich nachteilig auf die Biodiversität und ganze Ökosysteme auswirken kann. Daher wird künstliches Licht, das den natürlichen Rhythmus zwischen Licht und Dunkelheit verändert und auf diese Weise die Umwelt ‚verschmutzt‘, mittlerweile als schädlich angesehen. Insbesondere Fledermäuse leiden unter Lichtverschmutzung, da ihre Sinne an das Jagen und Orientieren in Dunkelheit angepasst sind. Zum Beispiel verzögert künstliches Licht den abendlichen Ausflug aus dem Quartier, beeinflusst ihr Jagdverhalten, beeinträchtigt ihre Orientierung und verlangsamt das Wachstum der Nachkommen. In chapter 1 gebe ich einen Überblick über den derzeitigen Stand der Wissenschaft und fasse die Auswirkungen von künstlichem Lichts auf Physiologie und Verhalten von Fledermäusen zusammen. Zudem diskutiere ich den Zusammenhang zwischen Phototropismus von Insekten und der Aktivität lichttoleranter Fledermäuse und beantworte die Frage, warum lichtscheue Fledermäuse diesem Muster nicht folgen. Im Anschluss betrachte ich die Auswirkungen künstlichen Lichts auf der Ebene des Ökosystems und schlage Maßnahmen vor, die geeignet sind, die schädlichen Effekte zu verringern. Eine wichtige Erkenntnis aus chapter 1 ist, dass die meisten Studien bisher Insekten fressende Fledermausarten der gemäßigten Breiten untersucht haben, obwohl die Diversität in tropischen Gegenden bedeutend höher ist. Tropische Fledermäuse besetzten zentrale Positionen im Ökosystem und vollbringen entscheidende Ökosystem- Dienstleistungen. So bestäuben Nektar trinkende Fledermäuse die Blüten einer Vielzahl ökologisch und wirtschaftlich wichtiger Pflanzen und Früchte fressende Arten verbreiten deren Samen. Um herauszufinden, wie sich Straßenbeleuchtung auf die Nahrungssuche fruchtfressender Fledermäuse auswirkt, habe ich Verhaltensexperimente mit Carolllia sowelli sowohl im Flugraum als auch im Freiland durchgeführt (chapter 2). Carolllia sowelli stellt in vielen Gegenden der Neuwelt-Tropen einen wichtigen Samenverbreiter von Pionierpflanzen dar. Ich konnte zeigen, dass C. sowelli in beleuchteten Arealen weniger Früchte erntet als von unbeleuchteten Kontrollpflanzen. Wenn dadurch auch die Samenverbreitung vermindert wird, könnte künstliches Licht weitreichende Folgen für die Regeneration von Wäldern haben und Neotropische Ökosysteme gefährden. So wie C. sowelli vermeiden es auch einige Insekten fressende Fledermausarten in beleuchteten Gegenden zu jagen. Andere Insekten fressende Arten hingegen reduzieren sogar ihren Jagdaufwand, indem sie gezielt Jagd auf Insekten machen, die von Straßenlampen angezogen wurden. Daher können Straßenlampen die lokale Artenzusammensetzung und folglich die Konkurrenz zwischen den Arten verändern. Allerdings unterscheiden sich die verschiedenen Lichtarten bezüglich ihres Einflusses auf Fledermäuse, abhängig von der spektralen Zusammensetzung ihres Lichts. In Europa und vielen außereuropäischen Ländern ist die Neuinstallation von Quecksilberdampf- (MV, Mercury Vapour) und anderen ineffizienten Leuchtmitteln bereits verboten und es wird erwartet, dass sie schrittweise vor allem durch LEDs (Light Emitting Diodes) ersetzt werden. Diese großflächige Umrüstung wird das Wellenlängen- Spektrum von Nachtlandschaften erheblich verändern. Daher ist es besonders für den Arten- und Naturschutz entscheidend zu verstehen, wie sich moderne LEDs bezüglich ihrer Auswirkungen auf Fledermäuse von herkömmlichen Leuchtmitteln unterscheiden. Um die Folgen einer solchen Umrüstung für Fledermäuse in urbanen Habitaten abschätzen zu können, habe ich die Fledermausaktivität an MV-Straßenlaternen, die durch LEDs ersetzt wurden, mit der Fledermausaktivität an Kontrolllaternen verglichen, die über den Zeitraum des Experiments durchgängig mit MV-Leuchtmitteln bestückt waren. In chapter 3 zeige ich, dass Pipistrellus pipistrellus, die häufigste Fledermausart an meinen Untersuchungsstandorten, ihre Aktivität in Folge der Umstellung auf LEDs um 45% verringert hat. Die Aktivität von Myotis spp., die Licht im Allgemeinen meiden, nahm hingegen an LED-Laternen um den Faktor 4,5 zu. Diese Ergebnisse deuten darauf hin, dass der großflächige Wechsel von herkömmlichen MV- Leuchtmitteln hin zu LEDs den anthropogenen Einfluss auf Fledermäuse verringert. Kurzfristig könnten manche Arten jedoch einen Nachteil durch eine geringere Jagdeffizienz an LEDs haben. Fazit: In meiner Doktorarbeit konnte ich demonstrieren, dass sich künstliches Licht nicht nur auf Insekten fressende sondern auch auf Früchte fressende Fledermäuse auswirkt. Zudem zeigen meine Untersuchungen, dass verschiedene Leuchtmittel Fledermäuse in unterschiedlichem Maße beeinflussen. Die Ergebnisse legen nahe, dass negative Auswirkungen künstlichen Lichts verringert werden können, indem konventionelle durch moderne, weniger schädliche Leuchtmittel ersetzt werden

Data from: Transition from conventional to light-emitting diode street lighting changes activity of urban bats

Light pollution is rapidly increasing and can have deleterious effects on biodiversity, yet light types differ in their effect on wildlife. Among the light types used for street lamps, light-emitting diodes (LEDs) are expected to become globally predominant within the next few years. In a large-scale field experiment, we recorded bat activity at 46 street lights for 12 nights each and investigated how the widespread replacement of conventional illuminants by LEDs affects urban bats: we compared bat activity at municipal mercury vapour (MV) street lamps that were replaced by LEDs with control sites that were not changed. Pipistrellus pipistrellus was the most frequently recorded species; it was 45% less active at LEDs than at MV street lamps, but the activity did not depend on illuminance level. Light type did not affect the activity of Pipistrellus nathusii, Pipistrellus pygmaeus or bats in the Nyctalus/Eptesicus/Vespertilio (NEV) group, yet the activity of P. nathusii increased with illuminance level. Bats of the genus Myotis increased activity 4·5-fold at LEDs compared with MV lights, but illuminance level had no effect. Decreased activity of P. pipistrellus, which are considered light tolerant, probably paralleled insect densities around lights. Further, our results suggest that LEDs may be less repelling for light-averse Myotis spp. than MV lights. Accordingly, the transition from conventional lighting techniques to LEDs may greatly alter the anthropogenic impact of artificial light on urban bats and might eventually affect the resilience of urban bat populations. Synthesis and applications. At light-emitting diodes (LEDs), the competitive advantage – the exclusive ability to forage on insect aggregations at lights – is reduced for light-tolerant bats. Thus, the global spread of LED street lamps might lead to a more natural level of competition between light-tolerant and light-averse bats. This effect could be reinforced if the potential advantages of LEDs over conventional illuminants are applied in practice: choice of spectra with relatively little energy in the short wavelength range; reduced spillover by precisely directing light; dimming during low human activity times; and control by motion sensors. Yet, the potential benefits of LEDs could be negated if low costs foster an overall increase in artificial lighting

Lewanzik_Voigt_2016_data

Lewanzik_Voigt_2016_dat

All data (bat activity) for Lewanzik et al 2019, J Anim Ecol

All data for Lewanzik et al 2019, J Anim Ecol, consisting of bat activity as a function of several predictors in a field playback study. All details are in the article

Data from: Insectivorous bats integrate social information about species identity, conspecific activity, and prey abundance to estimate cost-benefit ratio of interactions

Animals can use inadvertent social information to improve fitness‐relevant decisions, for instance about where to forage or with whom to interact. Since bats emit high‐amplitude species‐specific echolocation calls when flying, they provide a constant flow of inadvertent social information to others who can decode that acoustic information. Of particular interest is the rate of feeding buzzes – characteristic call sequences preceding any prey capture – which correlates with insect abundance. Previous studies investigating eavesdropping in bats yielded very different and in part contradictory results likely because they commonly focused on single species only, differed substantially in playback buzz rate, and did usually not account for (baseline) conspecific activity. Our goal was to overcome these limitations and systematically test which inadvertent social information bats integrate when eavesdropping on others and how this integration affects space‐use and both intra‐ and interspecific interactions, respectively. We used a community‐wide approach and investigated the effects of a broad range of playback feeding buzz rates and conspecific activity on eavesdropping responses in 24 bat species combinations in the wild. For the first time, we reveal that finely graded and density‐dependent eavesdropping responses are not limited to particular foraging styles or call types, but instead are ubiquitous among insectivorous bats. All bats integrated social information about calling species identity, prey abundance, and conspecific activity to estimate the cost‐benefit ratio of prospective interactions, yet in a species‐specific manner. The effect of buzz rate was multifaceted, as bats responded differently to different buzz rates and responses were additionally modulated by heterospecific recognition. Conspecific activity, in contrast, had a negative effect on the eavesdropping responses of all bats. These findings can explain the inconsistent results of previous studies and advance our understanding of the complex nature of con‐ and heterospecific interactions within bat communities. A comprehensive understanding of how bats incorporate social information into their decision‐making will help researchers to explain species distribution patterns and eventually to unravel mechanisms of species coexistence