Trapped in the darkness of the night: thermal and energetic constraints of daylight flight in bats

Bats are one of the most successful mammalian groups, even though their foraging activities are restricted to the hours of twilight and night-time. Some studies suggested that bats became nocturnal because of overheating when flying in daylight. This is because—in contrast to feathered wings of birds—dark and naked wing membranes of bats efficiently absorb short-wave solar radiation. We hypothesized that bats face elevated flight costs during daylight flights, since we expected them to alter wing-beat kinematics to reduce heat load by solar radiation. To test this assumption, we measured metabolic rate and body temperature during short flights in the tropical short-tailed fruit bat Carollia perspicillata at night and during the day. Core body temperature of flying bats differed by no more than 2°C between night and daytime flights, whereas mass-specific CO2 production rates were higher by 15 per cent during daytime. We conclude that increased flight costs only render diurnal bat flights profitable when the relative energy gain during daytime is high and risk of predation is low. Ancestral bats possibly have evolved dark-skinned wing membranes to reduce nocturnal predation, but a low degree of reflectance of wing membranes made them also prone to overheating and elevated energy costs during daylight flights. In consequence, bats may have become trapped in the darkness of the night once dark-skinned wing membranes had evolved

New Perspectives on Analytic Pragmatism

none2noAnalytic pragmatism is a framework of analysis elaborated by Robert Brandom, whose goal is to explain the relations between meaning and use according to a systematic and general method of inquiry. In April 2009, a workshop was organized to discuss the recent developments of this new theoretical approach. Brandom delivered three lectures, where he explored some aspects of analytic pragmatism and addressed the motivating themes of this enterprise, while the contribution from the other speakers ranged over specific aspects of the theory. This special issue is the outcome of that workshop. In this introduction we briefly outline the context of the debate and present the contribution to this issue selected from a much wider range of papers, using the reviewing process of Philosophia. © 2012 Springer Science+Business Media B.V.Santoro, Daniele; Penco, CarloSantoro, Daniele; Penco, Carl