Flower constancy in honey bee workers (Apis mellifera) depends on ecologically realistic rewards

Abstract

SUMMARYAs first described by Aristotle, honey bee (Apis mellifera) workers show a strong tendency to visit flowers of only one type during a foraging trip. It is known that workers rapidly learn a flower colour when rewarded with artificial nectar (sucrose solution). However, some previous studies report that the degree of constancy after training is unaffected by reward quantity and quality when bees are tested in an array of artificial flowers of two easily distinguished colours, such as blue and yellow. One possible reason for this surprising result is that large reward volumes were compared. This is likely to mask the abilities of foragers to make adaptive decisions under more realistic conditions. To test this possibility, we offered untrained honey bee workers ecologically relevant rewards (0.5, 1 or 2l of 0.5 or 1moll -1 sucrose solution) on one or two consecutive yellow or blue artificial flowers and then recorded which flowers the bees subsequently landed on in an array of 40 empty flowers. The results showed that an increase in all three factors (volume, concentration and number of rewards) significantly increased constancy (proportion of visits to flowers of the trained colour) and persistence (number of flowers visited) during the foraging bout. Constancy for the least rewarding situation was 75.9% compared with 98.6% for the most rewarding situation. These results clearly show that honey bee workers do become more constant to blue or yellow with increasing nectar rewards, provided that the rewards used are ecologically realistic. As the most rewarding conditions led to nearly 100% constancy, further reward increases during training would not have been able to further increase constancy. This explains why previous studies comparing large rewards found no effect of reward on constancy.

Persistence, reticence, and the management of multiple time memories by forager honey bees

“…Presumably, commitment to a single species is adaptive because it eliminates the period of time needed to learn flower handling and nectar extraction when switching to another species (Waser, 1986;Chittka et al, 1999). Honey bees show greater levels of flower constancy in artificial flower arrays when nectar volume, concentration or the number of nectar rewards is increased, providing that these factors are ecologically realistic (Grüter et al, 2011). Another possible explanation for flower constancy is a limited cognitive capacity (Dukas and Real, 1993).…”

Flower constancy in insect pollinators: Adaptive foraging behaviour or cognitive limitation?

“…That is, if the alternative colors are highly distinct in bee color space. However, a recent study 26 suggests that the reported inability of honeybees to adjust their flower choice according to differences in the rewards experienced was caused by the use of unnaturally large nectar (sucrose solution) rewards per flower (see ref. 27 and 28 for a similar argument).…”

Honey bee foraging distance depends on month and forage type

“…In other words, the farther a bee must fly to forage, the less available that forage is closer by (Seeley 1994;Seeley 1995). Bees have evolved exceptional sensitivity to measuring relative energetic rewards and to discovering new forage sources in the landscape, so a forager will only dance for the "best" forage sites known at any given time (Schmid-Hempel 1987;Schmid-Hempel and Schmid-Hempel 1987;Seeley 1994;Barron et al 2007;Grüter et al 2011). Therefore, each observed dance has already passed a cost/ benefit analysis and represents that bee's economically smart advice for where the colony should direct foraging efforts.…”