The sweet side of life: Nectar sugar type and concentration preference in Wahlberg's epauletted fruit bat J.C. Coleman ⁎, C.T. Downs School of Life Sciences, University of KwaZulu-Natal, P/Bag X01, Scottsville 3209, South Africa abstract article info Article history: Received 23 March 2012 Received in revised form 24 April 2012 Accepted 24 April 2012 Available online 1 May 2012 Keywords: Pteropodid Frugivore Sucrose Hexose Sugar preference Bat Nectar Fruit Whether nectarivores or frugivores place selective pressure on the plants they feed on, in terms of nectar or fruit traits, is much debated. Globally sugar preferences, concentration preference and digestive ability of avian nectarivores have been extensively researched. In contrast, relatively little is known about mammalian nectarivores or frugivores in terms of these, particularly Old World species. Consequently effect of sugar type and concentration on food preference in Wahlberg's epauletted fruit bat Epomophorus wahlbergi was inves- tigated. Pair-wise choice tests were conducted using equicaloric hexose and sucrose solutions at five different concentrations (5%–25%). It was expected that they would prefer hexose sugars as these are dominant in available indigenous fruits. However, bats preferred hexoses only when offered dilute (5%) concentrations. From 10% to 25% they showed a decrease in volume intake. Their body mass was generally higher and similar after feeding during the night with the exception of 5% concentration where the mean body mass decreased. When E. wahlbergi were offered a range of sucrose or hexose solutions (10%–25%) respectively, they showed no concentration preference in terms of total volume consumed, nor energy intake. These findings suggest that these fruit bats do not appear to act as a selective pressure on sugar composition in Old World fruit. In fruit bats with high energy requirements, dietary flexibility may be an advantage when faced with seasonal and unpredictable fruit availability. © 2012 Elsevier Inc. All rights reserved. 1. Introduction It has been suggested that groups of frugivores should show preference for particular sugars and sugar concentrations dominant in the fruits consumed (Baker et al., 1998). If these preferences re- flect the evolutionary interaction of frugivores with their food sources then they should present the predicted pattern when of- fered a choice (Herrera et al., 2000). Whilst the effect of sugar type and concentration on food preference in nectarivorous bird species has been the subject of numerous studies and is much de- bated (Lotz and Schondube, 2006; Brown et al., 2008, 2010a,b,c; Odendaal et al., 2010; Brown et al., 2011), there are relatively few studies on frugivorous or nectarivorous mammals, particularly aerial species. For the purposes of this paper, we refer to the familiar classifica- tion of bats into two suborders, Megachiroptera and Microchiroptera. Frugivory has evolved in two lineages of bats: Pteropodid and Phy- llostomid bats (Dumont, 2003). Members of the Pteropodidae (Sub- order Megachiroptera) are found throughout the Old World from Africa through Asia to Australia and on islands in the Indian and Pacific Oceans. In contrast, members of the Phyllostomidae (Suborder Microchiroptera) represent species endemic to the New World (Mickleburgh et al., 1992). Whilst the majority of Pteropodid species feed on fruit, a number of species rely on nectar as their primary source of food (Dumont, 2003). Consequently they may be consid- ered “nectarivores” in addition to frugivores. When processing fruit, Pteropodids press out and swallow juices from bitten fruit, whilst pulp, fibre and skin are pressed into ‘spats’ which they spit out (Morrison, 1980). Generally, sugar composition of fruits eaten by New World bats is low in sucrose and high in glucose and fructose (Baker et al., 1998). Despite this, in a study of one nectarivorous and two frugivorous New World bats, all species preferred sucrose over monosaccharides (Herrera, 1999). However, in another study no preference for sucrose over hexose was evident in nectarivorous bats (Rodríguez-Peña et al., 2007). Baker et al. (1998) analysed the sugar composition of fruits taken by Old World fruit bats. These fruits were higher in mean percentage sucrose compared with fruits taken by New World fruit-eating bats, and consequently they suggested that Megachiroptera actively search for food with high sucrose content. Nevertheless, the predominant sugars in these fruits were hexoses (Baker et al., 1998). Few studies have been conducted on sugar preference of Old World fruit- or nectar-feeding bats. No pattern of sugar preference was evident in a Comparative Biochemistry and Physiology, Part A 162 (2012) 431–436 ⁎ Corresponding author. Tel.: + 27 33 260 3594; fax: + 27 033 260 3697. E-mail address: colemanj@ukzn.ac.za (J.C. Coleman). 1095-6433/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.cbpa.2012.04.024 Contents lists available at SciVerse ScienceDirect Comparative Biochemistry and Physiology, Part A journal homepage: www.elsevier.com/locate/cbpa