Bees segregate between recently visited and unvisited flowers
That may not be news (the study in question* was published in 1992), but this is a rather interesting result… Bees are able to detect if flowers have been visited by another bee, and more readily leave those that have recently been. This behaviour is not difficult to explain: you better have to move if there is less to forage (don’t waste your time where reward is probably lower). Direct cues to assess nectar availability can be used by bees (when nectar content of a flower can be seen, or smelled), but this way isn’t always possible with any flower morphology and requires some level of inspection, i.e. there is a time cost. But bees are making the process easier by marking the flowers they visit with a special scent.
The effect of the scent was here experimentally reduced in the study (with artificial flowers) via an air extractor. When on, flower rejection dramatically decreased, flower inspection and visit time were also increased, while the number of visits was unchanged between the two experimental conditions. I find it amazing how far and finely tuned behaviours have evolved in these insects…
But we may also notice that the experimental flowers were still providing a great reward even after they were visited. This means bees in the experiment were stuck into their innate foraging method and losing resources aside. This probably means there is no such thing as a continuously rewarding flower in nature… :-)
M. Giurfa and J.A. Nunez (1992).Honeybees mark with scent and reject recently visited flowers. Oecologia 89: 113-117.
Filed under: Animals, English, Evolution, Insects, Pollination biology
[...] doesn’t (it is specialized on being pollinated by bees, which are contributing to the flower scent too, but for another reason [...]
Something like this seems so obvious, I am amazed it took a study.
It much less obvious than it seems, actually. For such a thing to evolve, it has to pay off. But producing a scent, usually a complex chemical, is costly (in terms of energy), and the cost is repeated over visits.
It can be selected if the cost is less than the gains, that is time spent not foraging already visited flowers allows to gather more resources than when visited flowers are investigated several times. But don’t forget flowers also produce nectar and stamens further dehisce, so the flower is not either full or empty…
My guess is that, bees make a living in huge colonies and communicate about flower fields (which they visit in high numbers), therefore the probability of a flower being visited is somewhat high. The cost of the behaviour may thus well be lower than the gains…
I would be curious as to whether other social hymenoptera evolved this characteristic too. E.g., bumblebees, living in much lower colonies, may not… But I don’t know if this question has been investigated yet…