All community members know about all roost locations How do Natterer’s Bats Myotis nattereri choose where to roost? Simone Mordue1, James Aegerter 2, Steven Rushton1, Aileen Mill1 1 School of Biology, Newcastle University, Newcastle Upon Tyne, UK. NE1 7RU 2National Wildlife Management Centre, Animal Health and Veterinaries Laboratories Agency, Sand Hutton, York, UK. YO41 1LZ. Introduction Bats have been described as exhibiting central place foraging (CP) behaviour. Indeed Rainho and Palmeirim 2011, concluded that distances to resources from the roost are determinant in the way bats forage across a landscape [1]. Conversely other studies have concluded that bats are faithful to their foraging patches returning to the same patch each night but roost selection is variable based on social decision making [2] and bats switch roost often whilst returning to the same patch to forage. Alternatively bats might respond to other drivers of behaviour to explain the spatial relationships between foraging patches and roost choices (e.g. thermal/energetic or epidemiological). Previous work with Natterer’s bats has suggested that they continually re-sort themselves across a restricted network of roosts and individuals within the community constantly move across this network [3]. Mortimer 2006, found that every individual bat he radio tracked used the same core foraging areas regardless of where they roosted [4].Here we attempt to address the CP foraging debate to determine whether distance to roost, social cohesion or another driver is key in roost selection for Natterer’s bats. Methods Natterer’s bats were caught on a weekly schedule using mist nets, hand nets and harp traps at Wallington National Trust Estate, Northumberland, UK during 2013 and 2014 A number of bats were fitted with Pica pip radio transmitters (Biotrack Ltd.) Day roost location was recorded for the life of each tag (approx. 7 days) At least 1 complete night of foraging activity was recorded per tagged bat Data was digitised using ArcMap v.10 Roost association data was visualised using R Studio and the package Igraph Assumptions All community members know about all roost locations Bats are faithful to their foraging patches (Qualitative support currently available - quantitative test will be eventually available) Bats largely move from roost to roost together (Qualitative support available) Results Figure 1. Igraph network of roosts. Nodes represent tree roosts and edges represent bat movement from roost to roost. Thicker lines represent higher use. Figure 2. Roost locations in Northumberland, UK and community 100% minimum convex polygon. Figure 3. Number of days (%) bats were recorded at each known roost 58 Natterer’s bats were caught, biometrics recorded and ringed 17 natural tree roosts were discovered (Fig. 2) 18 Individual bats have been radio tracked, 5 of those over two successive years Bats were very dynamic switching roost every few days (Fig.1 ) Bats returned to the same foraging area on successive nights of tracking Bats used roosts A, B and C most frequently despite alternative closer roosts being available to their foraging patches Average distance travelled from foraging site to nearest known roost was 2.8Km and to furthest roost was 3.9Km Figure 4. Natterer’s bat with forearm ring Figure 5. Natterer’s bat fitted with radio transmitter Conclusions Natterer’s bats at Wallington do not conform to the central place foraging theory and choose roost locations based on sociality rather than distance to foraging patch The social benefits of roosting together outweigh the extra time and energy needed to travel further to core foraging areas Further work is needed to understand the benefits of roosting together, who decides to move roost and why Work will be carried out in 2015 to address these questions and to further strengthen the roost network and build a social network of individuals References 1. Kerth, G., Causes and Consequences of Sociality in Bats. BioScience, 2008. 58(8): p. 737-746. 2. Daniel, S., C. Korine, and B. Pinshow, Central-place foraging in nursing, arthropod-gleaning bats. Canadian Journal of Zoology, 2008. 86(7): p. 623-626. 3. Rainho, A. and J.M. Palmeirim, The Importance of Distance to Resources in the Spatial Modelling of Bat Foraging Habitat. Plos One, 2011. 6(4) 4. Mortimer, G., FORAGING, ROOSTING AND SURVIVAL OF NATTERER'S BATS, MYOTIS NATTERERI, IN A COMMERCIAL CONIFEROUS PLANTATION, in University of St Andrews. 2006. 5. Smith, P.G., Habitat preference, range use and roosting ecology of Natterer's bats (Myotis nattereri) in a grassland-woodland landscape. 2001, University of Aberdeen.