Activity patterns of the lesser horseshoe bat Rhinolophus hipposideros at summer roosts

Abstract

Dusk to dawn observations, using a bat detector and occasionally an image intensifier, were made outside two nursery roosts of lesser horseshoe bats Rhinolophus hipposideros from late May to September. Emergence was correlated with sunset but delayed by extended twilight. Light intensity was important in triggering departure and cloud cover advanced it. Light‐testing behaviour was invariably undertaken, in the form of brief flights out and back into the roosts. The exit from one roost was shaded by trees and exploratory flights were generally more extended there. Heavy rain inhibited emergence. There was almost always intermittent activity throughout the night, with many individuals returning and departing, and no indication of seasonal or overnight peaks. A bat detector inside a third roost confirmed overnight observations at the other two. Some bats often returned to the roost for the night before dawn. Dawn return was linked to sunrise, prolonged twilight in midsummer hastening it. Colony size varied appreciably over periods of a few days and even overnight. There is some limited evidence that increased colony size, perhaps through social interaction, may have influenced timing of departure at dusk and return at dawn.

Roosting behaviour and phenology of the Lesser horseshoe bat (Rhinolophus hipposideros) in a breeding colony in Sintra, Portugal

“…In fact, the availability of aerial insects, daylight-length (McAney & Fairley 1988, Catto et al 1995, temperature (Lacki 1984, Russo & Jones 2003, Russ et al 2003, and other climatic factors as rainfall (Shiel & Fairley 1999), relative humidity (Lacki 1984) and wind speed (Russ et al 2003, Russo & Jones 2003 seemed to play an important role in the activity patterns of insectivorous bats. Some studies show that insectivorous bats present this bimodal pattern due to the exploitation of peaks of activity of aerial insects: a first peak in the number of insects usually occurs after dusk and a second just before dawn (Swift 1980, Rautenbach et al 1988, Jones & Rydell 1994).…”

“…Increased activity before the first departure was probably related to the fact that adult bats need to check levels of light intensity before leaving the roost (McAney & Fairley 1988, Seckerdieck et al 2005, Griffiths 2007, and thus perform several flights exiting and entering the roost before they definitely departure to forage (McAney & Fairley 1988). Light sampling plays an important role in the regulation of the nocturnal activity of several bat species and it is also one way of bats avoiding predators that need of at least some light to capture their prey ( Isaac & Marimuthu 1993, Griffiths 2007.…”

“…Wind and precipitation are also considered important factors affecting the foraging period of bats (Parsons et al 2003, Amorim et al 2012, Erickson & West 2002. For example, in Italy, strong winds decrease the activity of Myotis daubentonii and M. capaccinii (Russo & Jones 2003) and, in Ireland, R. hipposideros seems to be negatively affected by heavy rain (McAney & Fairley 1988).…”

Coletar morcegos por seis ou doze horas a cada noite?

“…É consenso entre os pesquisadores que as primeiras horas após o pôr-do-sol são as mais produtivas, com a taxa de captura declinando três a seis horas após (JONES et al 1996, MARINHO-FILHO & SAZIMA 1989, PEDRO & TADDEI 2002, AGUIAR & MARINHO-FILHO 2004. Na maioria absoluta das espécies de morcegos estudadas até o momento, a atividade noturna é sincronizada com o pôr-do-Sol (CHURCH 1957, HERREID & DAVIS 1966, BATEMAN & VAUGHAN 1974, ERKERT 1978, 1982, AVERY 1986, MCANEY & FAIRLEY 1988, ISAAC & MARITHMU 1993, CATTO et al 1995, KUNZ & ANTHONY 1996. A coleta por toda a noite tem a vantagem de amostrar todo o período de atividade das espécies de morcegos, mas resulta em grande desgaste físico, que é multiplicado em procedimentos que necessitam de noites consecutivas de trabalho.…”

Foraging activity of the free-tailed bat Molossus molossus (Chiroptera; Molossidae) in southeastern Brazil

“…Part of the captures were obtained in sunlight. In most studied bat species, activity is synchronised with sunset (Erkert, 1982;McAney and Fairley, 1988;Isaac and Marimuthu, 1993;Laborda and Cartwright, 1993;Catto et al, 1995;Kunz and Anthony, 1996;Weinbeer et al, 2006). …”