View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Stirling Online Research Repository i The Nesting Ecology of Bumblebees Stephanie Alexandra O’Connor 2013 A thesis submitted for the degree of Doctor of Philosophy Institute of Biological & Environmental Sciences School of Natural Sciences The University of Stirling ii Summary abstract Bumblebees have undergone dramatic declines both in Britain and further afield during the last century. Bumblebees provide a crucial pollination service to both crops and wild flowers. For these reasons, they have received a great deal of research attention over the years. However, the ecology of wild bumblebee nests and the interactions between nests and other species, particularly vertebrates has been somewhat understudied. This is largely due to the difficulty in finding sufficient nests for well replicated study and a lack of appropriate methods of observation. Here, methods for locating bumblebee nests were trialled. It was found that a specially trained bumblebee nest detection dog did not discover nests any faster than people who had received minimal instruction. Numbers of nest site searching queens provide a reliable indication of suitable nesting habitat (i.e. places where nests are more likely to be found). In order to investigate aspects of bumblebee nesting ecology wild nests were observed by filming or regular observations by either researchers or members of the public. Some Bombus terrestris nests were collected and all the bumblebees were genotyped to identify any foreign individuals. A review of British mammalian dietary literature was conducted to identify those that predate bumblebees. Great tits (Parus major) were filmed predating bumblebees at nests and it was clear from the literature and observations that badger (Meles meles), pine martens (Martes martes) and hedgehogs (Erinaceus europaeus) predate bumblebee nests, as well as the wax moth iii Aphomia sociella. No evidence for predation by any other vertebrate species was found. Behaviours recorded included parasitism by Psithyrus, apparent nectar theft and possible usurpation by true bumblebees, egg-dumping by foreign queens and drifting and drifter reproduction by foreign workers. These events may cause harm to colonies for example, through horizontal transmission of pathogens, or exploitation of the host nest’s resources). Alternatively where for example, usurpation by true bumblebees, egg-dumping or drifting is successful, these alternative reproductive strategies may increase the effective population size by enabling a single nest to produce reproductives of more than one breeding female. These data found that wild B. terrestris nests with a greater proportion of workers infected with Crithidia bombi were less likely to produce gynes than those with fewer infected workers. Gyne production also varied dramatically between years. There is a growing body of evidence that a class of frequently used insecticides called neonicotinoids are negatively impacting bumblebees. An experiment was conducted using commercial colonies of B. terrestris which were fed pollen and nectar which had been treated with the neonicotinoid imidacloprid at field realistic, sub-lethal levels. Treated colonies, produced 85-90% fewer gynes than control colonies. If this trend is representative of natural nests feeding on treated crops, for example, oilseed rape and field beans or garden flowers, then this would be expected to cause dramatic population declines. In this thesis methods for locating bumblebee nests have been tested, new behaviours have been identified (for example, egg-dumping by queens and predation by great tits) and estimations for rates of fecundity and destruction by various factors have been provided. iv Doubt has been cast over the status of some mammals as predators of bumblebee nests and estimates for gyne production, nest longevity, etc, have been given. More work is needed, especially observations of incipient nests as this is when the greatest losses are thought to occur. v DECLARATION I declare that the thesis has been composed by myself and that it embodies the results of my own research. Where appropriate, I have acknowledged the nature and extent of work carried out in collaboration with others. …………………………………………… Stephanie Alexandra O’Connor vi Acknowledgements I consider myself incredibly fortunate to have been given the chance to research bumblebees and especially bumblebee nests which have enthralled me for years. This fantastic opportunity and experience has been entirely due to Dave Goulson. I have enjoyed my time working with you immensely and I can’t imagine my project ever getting this far without your unfailing enthusiasm, support, optimism, and crucial “it’ll be fine” mantra! I can’t thank you enough for all your help. Kirsty Park has also provided a great deal of support during my project and her no- nonsense comments on my experimental design and manuscripts has been invaluable. I would also like to thank Luc and Matt for their input, particularly during my earlier years. Thanks are due to my many field assistants without whom this work would not have been possible, (I am of course delighted that I have been able to give the gift of ‘finding a bumblebee nest’ to so many)! I would like to say a huge thank you to the hundreds of people who reported and watched nests and to the land owners who allowed me to run experiments on their ground, as well as interfere with and occasionally abduct their bumblebees. In particular I would like to thank Iain MacFarlane, John Cross and the Muirhead Clan. Alison and Rowan Muirhead deserve a further mention for putting up with Toby and I as lodgers for several years. I like to think both have developed something of a love for bumblebees because of us! I would like to thank all staff in the department, both past and present for making my time at Stirling a true pleasure. There was always someone on hand to offer advice, plenty coffee vii room banter and engrossing seminars. In particular, Lynn for handling and explaining project accounts, Scott for his instruction on all computer related issues and Ronnie, James and Willy for assisting with various vague and urgent construction projects. I would also like to thank Juliet Osborne at Rothamsted Research for assistance with one chapter and also thanks to Gordon Port and Mark O’Neill at Newcastle for getting me interested in bumble bees all those years ago! The presence of the Bumblebee Conservation Trust was a key factor in my preference to become part of Stirling’s bumblebee research team. Through the BBCT and the University’s media team, I have had the opportunity to some of my work to public audiences on several television and radio programs. This has been both a great experience and useful in reminding me that there are many people in the real world, outside of academia who care deeply about the environment and bumblebees. Thank you to my wonderful husband Kerr, to Kay and all of the Cessford family for supporting me during my final years and not being too cross with my references to ‘intensification of agriculture’ or stirring up issues with insecticide legislation. My parents have always encouraged me to follow my love of animals and nature. I am grateful to them for supporting me during my first degree, keeping me on track through my time at Stirling and allowing me to collect plenty of pets while growing up! My brother James has been a source of constant support, and has always taken a keen interest in my work (which I like to think is because he sold out his science career for accountancy). As viii well as being good humoured, James inflicts an enraging brand of motivation by his refusal to acknowledge any defeatist or negative attitude, upon those around him. A far more sympathetic ear could always be found from my dear friend Claire Stead. Thanks to all of the bumblebee research team and other PhD. students who have assisted and supported me. Special thanks go to Nicky, Dani, Jenny, Jess, Penelope and of course Gillian. I wouldn’t have made it without you all and I certainly wouldn’t have such fond memories: (Terrifying midnight hose reels; getting stung in the ‘bee rearing-room’, dog walking and training, sweltering greenhouses and sitting out storms under hedgerows). I treasure every experiment that Gillian and I attempted; from the construction of 400 pointless bumblebee nest-boxes to the delights of queen collection in Ullerpool and surprisingly bee-free transects in the Scottish borders. Thank you for your constant help, advice and friendship, your confidence in me has been overwhelming throughout. Things didn’t go entirely to plan... Toby didn’t find as many nests as I’d hoped, the camera system employed was not the first one tested and my attempts at rearing nests from queens didn’t go too well. I mention these things because it wasn’t easy, and the people whom I have thanked in the above really had their work cut out. The completion of this project is as much of a credit to them as it is to me, so thank you all once again. ix Table of contents Summary Abstract……………………………………………………............................. ii Declaration………………………………………………………………........ v Acknowledgements………………………………………………………...... vi Table of contents…………………………………………………………….. ix Publications arising from this thesis................................................................. xii List of tables………………………………………………...……………….. xiii List of figures…………………………………………………...……………. xiii List of appendices…………………………………………………...……….