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Report of the March meeting.
What’s on the Mind of Pollen Gatherers? A talk by Dr. Natalie Hempel de Ibarra from the University of Exeter.
Natalie and colleagues have been researching the abilities and behaviours of bees when pollen gathering. Relevant questions they are trying to answer are:
- Do bees foraging for pollen have preferences for certain types of pollen?
- Do they know what they need to collect?
- Can they discriminate between pollen from different plants in favour of their nutritional requirements?
The plant’s point of view:
For the vast majority of flowering plants the goal is cross pollination, which will maintain or improve the gene pool and improve the species’ chances of survival. Many animals will pollinate by transfering pollen from flower to flower but pollen removal for feeding comes at a cost, both in terms of energy and lost reproductive potential.
In evolutionary terms pollen has been an insect food source for 100-120 million years. Nectaries appeared about 70 million years ago to attract pollinating insects and cut down on the energy-expensive production of pollen. This strategy was hugely successful as part of the expansion in new species around that time.
The bee’s point of view:
Bees are 100% dependent on flowers for their nutritional requirements, nectar and pollen.
When feeding, insects should:
- Make the lowest effort for the highest benefit and
- Reduce their exposure to toxins
Enormous variation in pollen nutritional quality exists within species and between populations, so how selective should bees be? The benefits of generalised foraging behaviour are:
- Wider diversity of nutrients
- More flexibility to collect sufficient pollen
- Adaptability to change
- Dilution of toxin intake
So, can bees distinguish pollen varieties by taste? The answer is ‘Probably yes’, although they have only 10 taste receptors (we have 5, bumble bees have 23). The bee brain is equipped for learning smell and taste so knowledge and experience of pollen taste could well be a driving force for efficient pollen collection, although the primary driver appears to be quantity of pollen collected. This may partially answer the first question of preferences for certain types of pollen.
To answer the second question, experiments in the past have focussed on whether foraging bees can determine the quality of pollen from different plant species, but without a great deal of success. More recent experiments have adopted a novel experimental approach testing the learning ability of bees with pollen rewards.
Bees possess receptors on their antennae, so individual bees in cages can be trained to extend their proboscis for a reward at the same time as the antennae are exposed to an odour (see image below). This conditioning failed to elicit a response with a variety of dry pollen samples. However experiments conducted with bumblebees and wet samples of varying concentration showed the bees’ ability to distinguish between pollen and pollen-surrogate differing in protein content. Bees preferred a particular pollen type, but this was not always the most concentrated sample. Only when presented with the biggest difference in concentration did the bees prefer the higher concentration.
Methods for experimental testing of pollen collection and pollen-rewarded learning in bees.
(a) When stimulated with pollen bees spontaneously respond with a proboscis extension (PER). The typical sucrose reward was substituted with pollen in an attempt to train honeybees to associate an unfamiliar odour with pollen reward.
(b) Bees accept pollen presented in Petri dishes, which can be presented on various coloured rings to test learned responses.
In conclusion it seems bees will use all the cues available to form their experience of pollen collection. These cues include taste, colour, ease of collection, abundance and possibly freedom from toxins.
- Do they have a preference for certain types of pollen? Yes
- Do they know what they need? No good evidence that they do, or indeed that they would have to.
- Can they discriminate nutritionally? To some extent, perhaps, but it is more important to collect large quantities and avoid toxins.
Images of experiments courtesy Natalie Hempel de IbarraCentre for Research in Animal Behaviour,
University of Exeter,
Exeter EX4 4QG
Dead Bees don’t Buzz – Surviving the Winter
Report of talk by Roger Patterson at the joint meeting of West Dorset and East Devon Beekeepers, January 2018
Roger started off by reminding us that bees are wild animals with a yearly cycle of nest expansion in the spring and contraction in autumn, and although they are very adaptable it is often the case that beekeepers work against the natural cycles leading to loss of bees through beekeeping errors.
Beekeeping advice is very variable, possibly based on human perceptions, and there is therefore a need to consider the situation from the bees’ point of view. Simply put they try to maintain population stability and prepare for the future.
In the wild it is definitely a question of survival of the fittest. Weak or diseased colonies are less adaptable and will die out, so wild colonies tend to be strong, healthy and adapted to their environment.
Roger went on to show how a wild colony behaves through the yearly cycle, with the cluster moving up to fresh stores in winter then the queen starting to lay in the empty cells below the nest as the weather warms up.
Other characteristics of successful wild colonies that we should take note of are:
- the bees tend to be dark
- nests are well above ground level and are therefore less prone to damp
- the entrance is defendable
- usually well insulated in a tree or building
- the interior is 100% propolised
- they always have their food stores above or behind the brood
- they tend to have the brood nest near the entrance
How can we copy them and improve our beekeeping and winter survival?
Allow the bees plenty of time at the end of the summer to arrange their stores where they want them. Consider putting frames “cold way” over winter to reduce the risk of isolation starvation.
With frames ‘warm way’ the cluster near the entrance (green area) will not move to stores at the back of the hive (red) during cold weather.
Make sure there is adequate air circulation round the hive to reduce dampness.
Ensure colonies going into winter are strong, healthy and well populated with plenty of young bees. A small colony can be given surplus frames of brood to boost numbers.
Unite weak colonies, especially those colonies with poorly performing queens.
When feeding in the autumn feed little and often to allow the bees to keep up with pollen collection and storage in proportion to the quantity of syrup, otherwise they will not have sufficient protein to produce healthy brood during the winter months.
Conditions are something the beekeeper can do something about. Remember that cold doesn’t kill bees but damp conditions do. Roger advised to always leave the tray out of the mesh floor for this reason. The beekeeper can also ensure protection against pests such as wasps, mice and woodpeckers.
Monitoring during the winter months usually involves hefting the hives. A word of warning! This only works if the stores are still liquid. Any honey which has solidified, such as ivy, will be unavailable to the bees.
The picture shows solidified stores next to the cluster preventing the bees from moving to liquid honey, just a few inches away, during cold weather. If in doubt feeding a small quantity of fondant will let you know whether the bees are ok or need help.
Finally, remember that Varroa has not gone away. You need to monitor throughout the year and do something about high counts BEFORE it gets out of control.