Seasonal changes in the foraging behaviour of Leisler's bats (Nyctalus leisleri) in Ireland as revealed by radio‐telemetry

Abstract

Leisler's bats Nyctalus leisleri, from two nursery colonies were radio-tracked from April to August in 2 years. They commuted directly to foraging sites up to 13.4 km away at speeds often exceeding 40 km h -1 . Except during lactation, individuals occasionally day-roosted away from the nursery in buildings or hollow trees. These were also sometimes used as night roosts, especially during rain, which also stimulated return to the nursery. On most nights the ®rst¯ight lasted the longest. During preparturition, when distances from roost to foraging site were greatest, and time spent¯ying per night (t F ) was least, there was often only one¯ight, with a second towards dawn on warmer nights, and occasionally a third. After parturition, in June, t F and the number of¯ights (N F ) increased up to weaning, corresponding to rising energy demands. But distances to foraging sites fell, rising only slightly in postlactation, presumably because insects, and thus feeding patches, were more abundant than in preparturition. N F fell to preparturition levels after lactation. Exploratory behaviour by juveniles intensi®ed with time ± distances to feeding sites, t F and the total distance¯own each night all increased; the distance¯own each night was eventually greater than any recorded for adults. Roosting away from the nursery was also more common. Before dispersal, there were extended migrations by juveniles outside the summer range of the adults. Distances moved by two dispersed juveniles exceeded 34 km. Two-thirds of the recorded foraging time was over pasture or drainage canals. Foraging over other habitats, particularly lake and conifer forest, was greatest in preparturition. Other habitats foraged included lights, estuary, stream, beach and dunes.

Foraging Behaviour and Habitat use by the European Free-Tailed BatTadarida teniotis

“…The median outgoing commuting flight speed (50.1 km/h), was about 2.5 times higher than the predicted Vmr (20.9 km/h). In fact it has been predicted that bat commuting flight speeds should exceed Vmr (Norberg, 1981), and this has been observed with other species, such as Pipistrellus pipistrellus (Jones and Rayner, 1989) and Nyctalus leisleri (Shiel et al, 1999). However, the observed discrepancy is particularly high, and this may be due to peculiar adaptations of molossids for highspeed flight (Vaugham and Bateman, 1980).…”

Variability of foraging and roosting activities in adult females of Daubenton’s bat (Myotis daubentonii) in different seasons

“…In line with our observation, Henry et al (2002) reported a pronounced decrease in home-ranges from pregnancy to lactation, resulting in analogical decrease in flight distances of observed little brown bats, Myotis lucifugus (LeConte, 1831). Accordingly, Racey & Swift (1985) and Shiel et al (1999) described similar patterns in spatial activity between pregnancy and lactation in pipistrelles, Pipistrellus pipstrellus s.l. (Schreber, 1774) and the lesser noctules, Nyctalus leisleri (Kuhl, 1817), respectively.…”

“…For example, pregnant females are forced to substantially reduce the use of daily torpor, an energy saving physiological mechanism, in order to diminish negative impact of low body temperature on the rate of developing embryos (Racey 1973;Racey & Swift 1981;Dietz & Kalko 2007). As a consequence, they have to compensate for increased energetic demands connected with fetal development by prolonging the time they spend on foraging bouts (Barclay 1989;Rydell 1993;Catto et al 1995;Grinewitch et al 1995;Shiel et al 1999;Dietz & Kalko 2007). However, as the size of embryos increases, the females' flying ability decreases and they have to use different compensatory mechanisms, such as roosting in thermally optimal roosts (McNab 1982) and/or aggregation onto large colonies in order to reduce thermal losses (Kurta et al 1987).…”

Influence of Habitat on the Foraging Behaviour of the Mediterranean Horseshoe Bat,Rhinolophus euryale

“…In fact, individual foraging areas in our study were significantly smaller than in Aihartza et al (2003: table 4) (U-test = 16, n 1 = 7, n 2 = 13, P < 0.05). Values close to or above 10 km have been recorded for bat species with a high aspect ratio (Barclay, 1989;Shiel et al, 1999;Barclay et al, 2000) or with a low aspect ratio but a large size (Arlettaz, 1995). Bats similar in size or in aspect ratio to R. euryale, however, travel shorter distances (e.g., Racey and Swift, 1985;Adam et al, 1994;Duvergé and Jones, 1994;Entwistle et al, 1996;Bontadina et al, 1999).…”

“…Secondly, so as to investigate the influence of habitat quality on the foraging behaviour of R. euryale we compared our results with those by Aihartza et al (2003), and hence the present study site was chosen within the same geographical area of that examined in this latter paper 57 km apart and both studies were conducted in the same season (Racey and Swift, 1985;Shiel et al, 1999). In this way, any observed difference between the two investigations was likely to reflect differences in habitat composition and quality.…”