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
Bee ecology
& movement
Pollination of crops
and wild plants
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
Oil seeds
Protein
• Wild plant pollination
• Birds & other wildlife rely on seed and fruit
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
Nectar &
pollen
Farming
Commercial
colonies?
Predation?
Disease?
What is affecting bumblebee populations?
X
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 of sown wild flower margin have on bumblebee
populations?
• 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
distance
quantity
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
100
50
0
-50
Searching – feeder removed
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
Most bees flew over 250m
Mean flight speed = 15.6 mph
200m
O
O
= bee flight path
flowering crops
= colony position
hedgerows
Osborne et al, (1999); Riley et al (1999)
How bees move around the landscape
distance
quantity
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
Plotted locations of foraging bees
De-coding dances at observation hives
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
LH
GK
BH
WH
500m
AT
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
n = 157
n = 558
n = 19
WH
BH
AT
500 m
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
2km
X
X
2km
X
X
X
X
X
X
X
X
X
X
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