Bees of a Feather Flock Together?

During my research as a graduate student, I noticed that often bumblebees would land on artificial flowers if other bumblebees happened to be on them.

White-tailed Bumblebees (Bombus lucorum) visiting Spear Thistle.
White-tailed Bumblebees (Bombus lucorum) visiting Spear Thistle. (This is a real flower; I used fake flowers in my research. Thanks to Warren Photographic!)

Are bees attracted to other bees? Could other bees serve as a cue as to where to find food? Unfortunately I didn’t have time to run any experiments to find out.

Then I recently came across a paper by the folks from the same bee lab where I studied at the University of Ottawa. And hooray: they ran some experiments!

The “participants” in their study were worker bumblebees who had never left the nest. They are referred to as “naïve” bumblebees. I’ve included a photo of  bumblebee nest below. Here, the nest is in a wooden box. In nature, the contents of the nest would look the same but it would be in a hole in the ground (probably in an old rat’s nest). Also, the nest would be pitch dark since it is underground. This is all that naive bees would have been exposed to.

Marked_Bumble_bees
Photo: Wikipedia. Labels: Me.

So, what did the folks in the bee lab do?

First, they took naïve bumblebees out of the nest one at a time, and gave them each the choice between: (1) one live bumblebee; (2) six live bumblebees; (3) one fake purple flower; (4) six fake purple flowers; (5) one black disc; (6) six black discs. This experiment was intended to show whether bees prefer other bees over inanimate objects.

Turns out that naïve bumblebees chose live bumblebees more often than everything else, and they especially preferred six bumblebees over just one.

In their next experiment, they gave naïve bumblebees the choice between: (1) six black discs moving slowly around in a circle by a clock motor; (2) six black discs that didn’t move; (3) six dead bees moving slowly around in a circle by a clock motor; and (4) six dead bees that didn’t move. This experiment was designed to see whether bees prefer moving objects, and especially if they prefer moving, bee-shaped objects.

They chose the dead bees! And especially the moving dead bees. This suggests that naïve bumblebees are attracted to moving, bee-like objects.

So what I saw, way back in the day, was likely an actual preference of the bees for other bees compared to unmoving, unoccupied flowers.

What fascinates me about this is that an animal with a brain the size of a grass seed comes equipped with “unlearned” preferences: bees seem to innately prefer some features of objects over others without having any prior experience with them.

But the big question is: Does a bumblebee experience or know that another bumblebee is a bumblebee? Or do they just experience the features of bumblebees? In other words, is the attraction of bumblebees to other bumblebees truly social behaviour? Or is it just preferences for a certain set of things in the environment?

Here is a link to the bee lab where I studied.

Here is the full citation for the article:

Walker, C. M., & Plowright, C. M. S. (2015). Single bumblebee leaving colony for first time seeks company. Behaviour, 152(15), 2127-2143.

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