Ball-Rolling Bumble Bees Just Wanna Have Fun Tiny, soccer-playing bees raise questions about the inner lives of invertebrates

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Ball-Rolling Bumble Bees Just Wanna Have Fun 
Tiny, soccer-playing bees raise questions about the inner lives of 
invertebrates 
 
Ball-rolling bumblebees have become 
the first known insects to “play,” 
researchers say. The scientists recorded these tiny fliers manipulating 
wooden balls again and again in a series of new experiments. 
When animals repeatedly engage in behavior that does not provide them 
with food, shelter or another immediate benefit, researchers consider the 
behavior play. Play with inanimate objects is widely observed in animals, 
although most examples come from mammals and birds, with no record of 
the behavior in insects until now. 
Animal play is one piece of the puzzle when determining whether a group of 
animals is sentient
—whether its members have inner feelings and 
experiences. Scientists consider mammals, birds, and increasingly 
cephalopods and fish to be sentient beings. “Eventually, this can tell us 
something more about whether [insects] are sentient,” says Samadi 
Galpayage, a graduate student in Lars Chittka’s lab at Queen Mary 
University of London and lead author of the new bumblebee study, which 
was published on Thursday in Animal Behaviour. 
In 2017 Chittka and other scientists taught bumblebees to roll balls in 
exchange for a sugary prize. To determine whether ball rolling could be a 
form of “play” in the new investigation, Galpayage, Chittka and their 
colleagues needed to take away the reward. First, they set up a system that 

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let bumblebees move in an unobstructed path to a sucrose solution in a 
feeding area. Along the path’s sides, the researchers placed small wooden 
balls of varying colors, some fastened to the floor and some loose. Bees 
could access the sucrose without interacting with the balls at all. 
Over 54 hours, the team observed each of the experiment’s 45 bees 
contributing to 910 total ball-rolling actions. Some bees returned again and 
again, moving the balls in various patterns. The researchers found that 
feeding and ball-rolling activities happened at different times and 
frequencies, indicating that the bees had different motivations for the two 
actions. Younger bees and male bees were especially interested in rolling 
the balls. 
In a later experiment, the scientists trained the bees to associate ball rolling 
with a certain chamber color. The bees then preferentially chose to enter that 
color chamber even when it was empty. 
While these results illustrate play behavior in the bees, Galpayage says, the 
research does not show any motivations for it. Determining whether the 
insects are playing for pleasure, for instance, would require analyzing which 
neurotransmitters activate during ball rolling. 
Olli Loukola, a behavioral ecologist at the University of Oulu in Finland, who 
led the ball-rolling study in 2017 and was not involved in the new work, also 
wonders about the behavior’s ultimate function. The interest in moving 
objects, he says, could be motivated by an “innate need to develop motor 
skills
.” 
Regardless of the play’s function, such studies can help researchers 
determine if a species is sentient, says Heather Browning, an animal welfare 
expert and philosopher at the University of Southampton in England. 
“We don't have a good grasp yet on what the relationship is between 
sentience and different behaviors,” says Browning, who was also not 
involved in the study. Evidence for many different characteristics, such as 
play behavior, complex brain structure and learning ability “raise the 
probability of sentience.” This study, Browning adds, “seems to be pointing 
in that direction.”