Exploring the world of honeybees and bumblebees

Dr Juliet Osborne

Dept of Plant & Invertebrate Ecology

Rothamsted Research Harpenden, UK

Rothamsted Research

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

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

Pollination by bees • For humans: 87 of world crop species require bee pollination: representing 35% of global food production (Klein et al 2007) Tree fruit Soft fruit Salad • Wild plant pollination • Birds & other wildlife rely on seed and fruit Oil seeds Protein Insects Birds Mammals

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

Commercial bumblebees

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

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

Bumblebees in decline in the UK No. b’bee species per 50x50km Before 1960 After 1960 In the UK, ranges of many

Bombus

species have shrunk Williams & Osborne (2009)

Comparing bumblebees with honeybees • About

69

species in the Europe (1 honeybee) • Bumblebees have annual colonies - need undisturbed nest sites - only 50-200 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

Nest sites Commercial colonies?

Nectar & pollen Predation ?

X Disease ?

Farming What is affecting bumblebee populations?

Effects of agri-environment schemes The “Big Bee project Farmers sow wild flower mixtures as part of agri-environment schemes Mixture contains red clover, white clover & birdsfoot trefoil What effect does the

area

populations?

of sown wild flower margin have on bumblebee • 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 • 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 Commercial bumblebees

How bees move around the landscape

quantity distance quality How do bees find nectar & pollen sources?

How far do they travel?

What is the impact on the colony?

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

How do bees explore and find food?

• Always see looped patterns • Use to predict which flower patches will be used in different landscapes • Can build into mathematical models Searching – feeder removed 100 50 -50 0 0 50 100 -50 Bumblebee searching on first flight Reynolds et al J Exp Biol (2007; 2009)

Where do bumblebees go?

Flights of bumblebees leaving a colony 200m

O O

= bee flight path = colony position Most bees flew over 250m Mean flight speed = 15.6 mph flowering crops hedgerows Osborne et al, (1999); Riley et al (1999)

How bees move around the landscape

quantity distance quality How do bees find nectar & pollen sources?

How far do they travel?

What is the impact on the colony?

Where do honeybees go: de-coding the dance

De-coding dances at observation hives Plotted locations of foraging bees

Distribution of honeybees on oilseed rape • 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 Proportions of bees of each colour observed, by field

Comparing foraging ranges between bee species

500m 2km 5km

common carder bumblebee earth bumblebee honeybees X X X X X X X X X X

X X X X X

2km 2km 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?

Acknowledgements

Rothamsted bee team

Funders

BBSRC Defra CB Dennis Trust Game & Wildlife Conservancy Trust Syngenta

Collaborators

Prof Lars Chittka Prof Rob Paxton Prof Dave Goulson - Stirling Dr Claire Carvell – CEH Dr Dave Chandler – Warwick http://www.rothamsted.bbsrc.ac.uk/pie/JulietOsborne.html