Nectar preferences in male bumblebees
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Insectes Sociaux
RESEARCH ARTICLE
Nectar preferences in male bumblebees M. Brown1 · M. J. F. Brown1 Received: 6 August 2019 / Revised: 2 January 2020 / Accepted: 25 January 2020 © The Author(s) 2020
Abstract Social insect males are relatively understudied, but knowledge of their biology is increasingly important for conservation of declining groups. Bumblebees are important pollinators in temperate, sub-arctic, and Alpine regions, but many species are in decline across the globe. Agri-environment schemes have been designed to support female bumblebees, but free-living males may also need support. Male bumblebees have an energetically expensive lifestyle, and so understanding their foraging choices may provide a first step towards designing interventions to support them in the wild. Using a series of controlled laboratory choice experiments, we demonstrate that males prefer sugar concentrations of between 50 and 60% when under either simple (binary) or complex (octanary) choice conditions when presented with a broad range of sugar concentrations. When presented with concentrations within this preferred range, males exhibit a clear preference for sugar solutions of 56% w/w sucrose when solutions differ by 4%. These results suggest that males maximise their rate of energy intake, as predicted by theoretical models, rather than minimise their water consumption. In the future, male preferences for high sugar concentrations can be combined with knowledge of baseline nectar concentrations and flower phenology to maximise the value of conservation interventions for this neglected sex. Keywords Bombus · Foraging choice · Optimal foraging · Males
Introduction The study of social insects has largely, and understandably, focused on the biology of workers and queens. Males, as transient members of the population, have often been viewed as ‘flying sperm’ and have elicited comparatively little study (Baer 2003; Boomsma et al. 2005). However, male biology is as important as female biology for understanding reproductive success in most species, and thus is particularly important to investigate in groups of conservation concern. Bumblebees are a species-rich genus of annual social insects that play an important role as pollinators in temperate, Alpine, and sub-arctic ecosystems (Alford 1975). Over the last 30–40 years, it has become clear that many species of bumblebee are suffering severe declines across Europe (Williams 1982; Fitzpatrick et al. 2007; Nieto et al. 2014), North America (Cameron et al. 2011), South America (Morales et al. 2013), and Asia (Xie et al. 2008). These declines are * M. J. F. Brown [email protected] 1
Department of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
driven by a range of factors, including habitat loss, agricultural intensification, climate change, invasive species, and parasites (Goulson et al. 2008; Williams and Osborne 2009; Williams et al. 2009; Goulson et al. 2015; Arbetman et al. 2017). Given their importance as pollinators, and their charismatic
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