Bees use natural GPS to get home at night


Go to a park on a hot summer day and you won’t be surprised to see bees coming in and out of flowers. They drink the nectar from the flowers and collect the pollen from the flowers. Then, depending on the type of bees they are – we know 20,000 species in the world – they return to their hives or nests.

In the rainforest of Barro Colorado Island in Panama, you will only encounter native sweat bees (Megalopta genalis) at night. They collect nectar and pollen just after sunset and about an hour before sunrise.

It’s so dark at such times that “if you reach out as far as you can, you won’t be able to see your thumb,” says William Wcislo (pronounced wice-lo). He is a principal investigator at the Smithsonian Tropical Research Institute in Barro Colorado.

How can these green and golden bees find their way around in such a dim light? This was the question Wcislo and his Swedish collaborators wanted to ask. The trick to studying animal behavior, Wcislo says, is “to know what (animals) are trying to do so that you can ask questions so that they are able to tell the answer.”

For bees and wasps, we know that once they have obtained food, “they try to get home and they have the ability to navigate very complex environments,” says Wcislo. One of the ways they do it is the same as that of humans.

We memorize landmarks like a train station or Starbucks that show us how to get home. Sweat bees do it too. When the bees leave the twig nests they build hanging from branches, “they turn around and face the nest and fly around it. They learn where the Starbucks is, ”says Wcislo.

How do they see the nest in the dark? The researchers may have thought they were looking at the forest canopy, where the globular patterns of the night sky appear slightly brighter against the leaves of the ultra-dark trees. Do bees recognize these patterns to return home?

Researchers built nests with different patterns of black and white stripes on their entrances. The bees could find the nest that matched the pattern they memorized when they left the house even if the researchers moved its location.

This ability to navigate using forest canopy models, says Wcislo, “is quite remarkable. It shows that this is a sensory world and that what these bees pay attention to is richer than we previously thought. “

It also shows that light pollution (too much artificial light) could confuse bees and other animals active at night: they need total darkness to navigate their way. Wcislo says the good news is we can prevent light pollution.

For example, people can program highway lights to go out when there are no cars on the road, and we can use different wavelengths of light that don’t bother animals. .

“If we want plants and fruits, we need pollinators” such as sweat bees, says Wcislo. And by figuring out what they need to navigate, we can do a better job of helping to retain them.

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