Exploring the world of honeybees and bumblebees Dr Juliet Osborne Dept of Plant & Invertebrate Ecology Rothamsted Research Harpenden, UK

The world’s oldest agricultural research institute ensuring enhanced and environmentally sustainable crop production Rothamsted Research

Aims: To protect and promote: Honeybee & wild bee populations Crop & wild flower pollination Bee & pollination ecology at Rothamsted Bee ecology & movement Pollination of crops and wild plants How agriculture affects bee populations

Pollination by bees Tree fruitSoft fruitSaladOil seedsProtein For humans: 87 of world crop species require bee pollination: representing 35% of global food production (Klein et al 2007) Wild plant pollination Birds & other wildlife rely on seed and fruit InsectsBirdsMammals

Talk outline Different bee species essential for pollinating different plants Commercial bumblebees Bumblebee on raspberry Honeybee on oilseed rape Honeybee decline …..and possible explanations Bumblebee decline …..and possible explanations The research: why study bee movement?

Global trends: honeybees & insect-pollinated crops Aizen et al (2009) Current Biology Trends from 1961 to 2006 A) change in no. hives B) change in crop production

National trends in domesticated honeybee stocks Declines may be economically or politically driven Current major honey exporters Trends vary in Europe Aizen et al (2009) Current Biology

What are the causes of honeybee declines? Not necessarily biological: can be economic and political Different causes in different countries Expert view is that losses are caused by combination of factors Varroa mites & associated viruses are very important Need more evidence of colony level effects of food availability, sublethal effects of pesticides and interactions with disease. Are honeybee colonies reaching a threshold for collapse based on a combination of factors? We are building models to explore and predict the effects of interactions between in-hive & landscape factors on bee colony strength

No. b’bee species per 50x50km Before 1960After 1960 Williams & Osborne (2009) In the UK, ranges of many Bombus species have shrunk Bumblebees in decline in the UK

About 69 species in the Europe (1 honeybee) Bumblebees have annual colonies - need undisturbed nest sites - only bees in colony (h’bees have 60,000) They don’t make honey - need continual succession of flowers - not managed in hives No varroa mite; but have other diseases – not as well studied as honeybees Forage in cooler conditions Much better at pollinating tomatoes, peppers, beans, clover Comparing bumblebees with honeybees

X What is affecting bumblebee populations? Predation ? Commercial colonies? Disease ? Nest sites Nectar & pollen Farming

Effects of agri-environment schemes Farmers sow wild flower mixtures as part of agri-environment schemes Mixture contains red clover, white clover & birdsfoot trefoil What effect does the area of sown wild flower margin have on bumblebee populations? The “Big Bee project Growing on intensive arable farms boosts bumblebee density more Size doesn’t matter: 0.25 Ha plots were as effective as 1 Ha plots Heard et al 2009; Carvell et al (in press)

Talk outline Commercial bumblebees Bees and Pollination Honeybee decline & possible explanations Bumblebee decline & possible explanations The research: why studying bee movement is important Bees must find flowers in a very fragmented landscape …and fly home again Colony survival affected by energy and time spent searching for flowers, and flying to forage Predation, pesticide exposure and pollen movement influenced by foraging range

quantity distance quality How do bees find nectar & pollen sources? How far do they travel? What is the impact on the colony? How bees move around the landscape

Tracking bee movement with harmonic radar Harmonic radar Produces geometrically accurate maps of insect flight Transponder is 16mm long and requires no battery range: horizontal 1 km, vertical 5 m Honeybee, with radar transponder (aerial) Riley et al 1996

How do bees explore and find food? Bumblebee searching on first flight Always see looped patterns Use to predict which flower patches will be used in different landscapes Can build into mathematical models Reynolds et al J Exp Biol (2007; 2009) Searching – feeder removed

flowering crops hedgerows = bee flight path = colony position Most bees flew over 250m Mean flight speed = 15.6 mph Where do bumblebees go? O O 200m Flights of bumblebees leaving a colony Osborne et al, (1999); Riley et al (1999)

quantity distance quality How do bees find nectar & pollen sources? How far do they travel? What is the impact on the colony? How bees move around the landscape

Where do honeybees go: de-coding the dance De-coding dances at observation hives Plotted locations of foraging bees

Placed 18 colonies on a 1.3 km transect across Rothamsted farm. Powder dye added to each colony (one colour per site) Scored number of marked bees on 5 oilseed rape fields Distribution of honeybees on oilseed rape

736 marked bees were seen (constituted 67% of foraging bees) Most bees were on nearest field to their hives Bees foraged further from colonies as flowers dropped Distribution of honeybees on oilseed rape Proportions of bees of each colour observed, by field

Comparing foraging ranges between bee species X XX XX 2km 500m common carder bumblebee 2km earth bumblebee X XX XX 2km 5km honeybees X XX XX 2km Foraging range affects bee survival via food intake; but also risks of predation and exposure to pesticides Foraging range will affect pollen movement between crop fields

What next? Honeybees and bumblebees are in decline in Europe –Need better records of trends: not just overwinter mortality Pathogens and pests: –Target new Varroa control methods –Target beekeeping practices….education Poor nutrition & nesting sites: –Targeted agri-environment schemes work – grow legumes! –Target habitats: Arable, grassland, urban Pesticides: –More evidence required on sublethal effects & interactions –Encourage farmer / beekeeper interactions –Think about domestic horticulture?

Collaborators Prof Lars Chittka Prof Rob Paxton Prof Dave Goulson - Stirling Dr Claire Carvell – CEH Dr Dave Chandler – Warwick Funders BBSRC Defra CB Dennis Trust Game & Wildlife Conservancy Trust Syngenta Acknowledgements Rothamsted bee team