The importance of water bodies for insectivorous bats in a Malagasy dry deciduous forest: A case example from Kirindy (CNFEREF) Elias Bader1, Marta Acácio2 & Ara Monadjem3,4 Résumé détaillé 1Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, Dans les environnements saisonniers, les ressources 8057 Zurich, Switzerland alimentaires fluctuent généralement au cours de E-mail: [email protected] l’année. Les chauves-souris, qui sont des petits 2Centre for Ecology, Evolution and Conservation, vertébrés endothermiques, comptent sur des School of Environmental Sciences, University of East nourritures abondantes et régulières. Pour assurer Anglia, Norwich, NR4 7TJ, UK leur besoin énergétique dans un habitat où ces E-mail: [email protected] ressources sont rares, elles sont supposées se 3 Department of Biological Sciences, University of regrouper dans des endroits où la nourriture est plus Swaziland, Private Bag 4, Kwaluseni, Swaziland abondante, tels que dans les cours d’eau temporaires E-mail: [email protected] ayant encore de l’eau d’une forêt sèche caducifoliée. 4Mammal Research Institute, Department of Zoology D’autre part, l’accès à l’eau est peut-être encore plus and Entomology, University of Pretoria, Pretoria, South essentiel. Nous avons testé ces hypothèses dans Africa E-mail: [email protected] la forêt sèche caducifoliée de Kirindy (CNFEREF), Madagascar en enregistrant les activités de chauves- souris dans trois différents habitats : tout près de Abstract quelques bassins d’eau stagnante ou des lits de rivière asséchés, dans la forêt le long des lits de la In seasonal environments, food supply typically rivière et dans la forêt éloignée de cours d’eau. fluctuates during the course of the year. Bats, as Les cris de chauves-souris ont été enregistrés small endothermic vertebrates, rely on regular and avec un « Batlogger » posé sur le sol et tourné abundant food sources. To assure this in a habitat respectivement vers l’eau et la zone ouverte. Pendant where these resources are scarce, bats are thought 10 nuits entre le 13 novembre et le 27 décembre to aggregate in areas where food abundance is 2011, 1349 chauves-souris sont enregistrées au highest, such as the last remaining water bodies in niveau des 91 points d’échantillonnage, dont chaque dry deciduous forests in the dry season. Further, point est échantillonné pendant 5 mn. Ces cris sont access to water is perhaps equally or even more uniquement attribués au niveau de la famille en essential. We tested these hypotheses in Kirindy raison des incertitudes sur l’identification acoustique Forest (CNFEREF) in central western Madagascar des certaines espèces de chauves-souris malgaches. by recording bat activity with a Batlogger in three Nous avons mesuré la structure de la végétation different habitats: at pools with standing water (in a et l’abondance des insectes à l’aide d’une nouvelle dry riverbed), in riparian forest along the riverbed, méthode facile à utiliser et efficace. and in forest away from the riverbed. We measured Globalement, les activités de chauves-souris sont vegetation structure and insect abundance using plus élevées sur les lits de rivière, en particulier au a simple and effective new method. We found niveau des bassins, et plus bas dans la forêt galerie. that bat activity of the families Vespertilionidae Cependant, les différentes familles ont montré and Hipposideridae, was highest at the pools and différentes tendances. Nous avons constaté que best predicted by distance to water and vegetation les activités de Vespertilionidae et d’Hipposideridae structure. For the Molossidae, activity did not vary sont significativement plus élevées dans les bassins between habitats. The water pools appeared to have et aisées à prédire à partir de la distance au point an influence on bat community structure and seem d’eau et de la structure de la végétation. Pour les to play an important role on bat survival in fluctuating Molossidae, leurs activités ne semblent pas varier environments such as the dry deciduous forests of entre les différents habitats. L’analyse « Biota and/or central western Madagascar. Environment matching » ou BIOENV a montré que la Key words: Bat activity, acoustic monitoring, Kirindy distance des arbres les plus proches et la distance CNFEREF, Madagascar, dry deciduous forest par rapport à la rivière sont les variables qui ont une Bader, E., Acácio, M. & Monadjem, A. 2015. The importance of water bodies for insectivorous bats in a Malagasy dry deciduous forest: A case example from Kirindy (CNFEREF). Malagasy Nature, 9: 88-96. Bader et al. : The importance of water bodies for insectivorous bats 89 forte corrélation avec la structure de la communauté, considerable specific differences (Meyer et al., 2004; même si aucune des corrélations n’est significative Bader et al., 2015). au sein de la communauté. Toutefois, les bassins In this study, we aim to unravel the factors that semblent avoir une influence sur la structure de la determine the activity of insectivorous bats in a communauté des chauves-souris. highly seasonal dry forest habitat in central western Nos résultats montrent que les activités de Madagascar. More specifically, we investigated how chauves-souris sont plus élevées à proximité des forest structure, insect abundance and distance to zones où il y de l’eau que dans les endroits loin de the nearest water source affect the occurrence and celles-ci et que l’eau elle-même semble avoir un activity patterns of bats. impact plus important sur leurs activités que sur l’abondance des insectes. Ainsi, les cours d’eau, Materials and methods fluctuant dans des environnements tels que la forêt Study site sèche caducifoliée de l’Ouest malgache, semblent The study took place in Kirindy (CNFEREF) Forest jouer un rôle important sur la survie des chauves- (20º 03’S, 44º 39’E, 30-60 m above sea level), a dry souris. deciduous forest 60 km north of Morondava, central Mots clés : activités de chauves-souris, suivi western Madagascar. This area is characterized acoustique, Kirindy CNFEREF, Madagascar, forêt by pronounced seasonality, with a hot wet season sèche caducifoliée generally from December to March/April and little or no rain from May to November (Sorg & Rohner, Introduction 1996). The annual average rainfall is 900 mm (Kappeler & Fichtel, 2012). Vegetation comprises In a highly seasonal habitat, resources are unevenly well-developed undergrowth and a dense canopy, up distributed during different portions of the annual to 25 m above ground (Rakotonirina, 1996). cycle. To survive in this fluctuating environment, The Kirindy River that bisects this forest is largely animals have developed various adaptations. Some waterless during the dry season. In mid-November, species in areas with seasonally limited food supply when the first sampling was conducted, only three store fat and enter torpor (Kobbe & Dausmann, pools were left in the section of the riverbed within 2009; Genoud & Christe, 2011; Yang & Wang, 2011) our study area, which was assumed to be the or migrate to areas where the conditions are more only water source in a radius of at least several favorable (Berthold, 2001). kilometers. During the second sampling period, by In areas where water supply is limited, some the end of December, only one pool remained. Data species manage to minimize their water needs, were collected along the foot trails of the grid system enabling them to cover it through food intake only CS7, installed by the German Primate Centre (DPZ), (Grenot, 2001). Insectivorous bats, due to their Göttingen, and along the dry riverbed, covering an generally small size and disproportionately large area of approximately 2.2 km2. surface area created by the non-insulated wings, have a high basal metabolic rate (Kurta et al., 1990) Data collection and therefore are likely to rely on a regular food and water supply. During the dry season, insects are Acoustic data were collected between 13 and 20 sparse in forest habitats (Lack, 1986) but may be November, as well as on 26 and 27 December 2011. more abundant in close proximity to water sources. Sampling points were located every 50 m along the This can lead to increased activity of insectivorous riverbed. Away from the river, points were sampled bats in riparian areas (Grindal et al., 1999; Francl, every 50 m for the first 200 m and every 100 m 2008; Monadjem & Reside, 2008; Monadjem et al., thereafter. Distances in the forest were measured 2009). In regions with a pronounced dry season, this using the grid system, and the points in the riverbed effect may even be stronger due to the temporary were recorded with a Garmin 60 CSX GPS. During drying up of water bodies. On several continents, each night of data collection, three habitat types were it has been shown that the presence and activity sampled randomly: 1) riverbed, 2) forest (away from of bat species is related to habitat structure (Gehrt the riverbed) and 3) three pools (within the riverbed). & Chelsvig, 2003; Peters et al., 2006; Mueller et Sampling commenced at 19:00 (November) or 19:30 al., 2012). Among insectivorous bats, however, (December) and ended by 22:30. All recordings the preferred habitat type and structure show were made during the first quarter of the lunar phase 90 Bader et al. : The importance of water bodies for insectivorous bats hence, bias caused by moonlight was assumed to be et al. (2010b) and Goodman (2011). The genus negligible. The temperature during sampling periods Triaenops has recently been assigned to a separate ranged from 24.7°C to 31.0°C. family, the Rhinonycteridae (Foley et al., 2015), but for Bat activity was recorded with a Batlogger (www. this study we retain the genus in the Hipposideridae batlogger.ch), a real time ultrasound recorder, placed due to the similarity of their call structure (Monadjem on the ground at a 45º angle, pointing towards the et al., 2010b).