How far can a bee fly, and why should we care?
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Honeybee (Apis mellifera) landing on a milk thistle flower (Silybum marianum). Image credit, Fir0002/Flagstaffotos.Entomologists from Switzerland have published a study that measures how far three different species of bees can fly to forage for food.
Their study is innovative because it uses a new, direct experimental approach in which patches of host plants were moved progressively farther back from the nest over time. Antonia Zurbuchen and fellow authors measured the number of female bees that were able to forage at the patch at each distance.
Hoplitis adunca female on its host plant Echium vulgare. This is one of the bee species from the study. Image credit, Antonia Zurbuchen.This research question is crucial for addressing the widespread decline in bee species. Development, road building, intensive agriculture, and other disturbances to the landscape have expanded the spatial gaps between bees' nests and their host plants (i.e. food sources). This is especially problematic given the important pollination services that bees provide in the ecosystem.
The study found that the maximum foraging distance recorded was 1100 meters for the small Hylaeus punctulatissimus, 1275 meters for the medium sized Chelostoma rapunculi and 1400 meters for the large Hoplitis adunca. This is farther than expected based on the size of the bees and the results from past studies.
However, they found that for two of the species, at least 50% of the individuals were not able to forage more than 300 meters. From a conservation perspective, these results show that the metric of maximum foraging distance alone is not entirely useful, because it may be much greater than what much of the population is actually able to fly. Therefore, it may overstate the maximum distance between a nest and the closest food source that can sustain a population.
The authors note that past studies on bee flight have largely focused on maximum distance while ignoring the distance that a sizable proportion of the population can fly to forage. They write,
"For the conservation of bee populations knowledge of threshold distances at which for example 50% of females discontinue their foraging activity is supposed to be more important than the mere knowledge of species specific maximum foraging distances covered only by a small proportion of individuals. Such threshold distances may be substantially shorter than maximum foraging distances as shown in the present study, indicating that a close neighborhood of nesting and foraging habitats within few hundred meters is crucial to preserve populations of bees."
--Reviewed by Rob Goldstein
A. Zurbuchen, L. Landert, J. Klaiber, A. Müller, S. Hein, and S. Dorn (2010). Maximum foraging ranges in solitary bees: only few individuals have the capability to cover long foraging distances Biological Conservation: 10.1016/j.biocon.2009.12.003
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