First posted on 07-31-2014
Bumblebees are able to connect differences in pollen quality with floral features, such as petal color, and so land only on the flowers that offer the best rewards, according to a new study by researchers at the University of Exeter. The study used bumblebee foragers housed under controlled conditions to test whether the bees learn about flowers during pollen collection.
Bees do not ingest pollen while foraging on flowers, only nectar. It has been unclear whether they are able to form associative relationships between what a flower looks like and the quality of its pollen. Test results indicate that bumblebees can individually assess pollen samples and discriminate between them during collection, quickly forming preferences for a particular type of pollen.
The findings show that pollen foraging behavior involves learning and individual decision-making, which may allow bees to quickly learn which flowers provide the most nutritious pollen rewards for rearing their young.
Dr. Natalie Hempel de Ibarra, one of the researchers, said “There is still very little known about how bees decide which flowers to visit for pollen collection. Easily learning floral features based on pollen rewards, without needing any nectar rewards, is a fast and effective way to recognize those flower species which bees have previously experienced to be the best ones.”
Another member of the team, Dr. Elizabeth Nicholls, added that “Bees need to be able to select flowers providing the most nutritious food for rearing their young. Since bumblebees don’t eat pollen when foraging, it was unclear if or how they might be able to assess differences in quality. Here we’ve shown that they are able to detect differences in pollen, even before landing, which means they may be able to tell, just from the colour of the petals, which flowers are worth visiting.
“We already know a lot about how and what bees learn when collecting nectar from flowers, but since bees don’t eat pollen when foraging, we were interested to see whether they could still learn which flowers to visit when collecting this resource.”
The experiments involved manipulating the quality of pollen offered to the bees by diluting the samples. The researchers examined what they preferred to collect, if they could differentiate quality before landing by only letting the bees smell and see the pollen rather than probing it; and presenting the bees with four different colored discs containing stronger and less diluted pollen to record preferences and change of preferences over time.
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