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A trio of researchers, one a zoologist, another a primatologist and the third a linguistics professor, from Institut Jean Nicod, Heinrich Heine University and the University of Oslo, respectively, have discovered that female gibbons engage in a strange type of robotic dancing.

In their posted on the bioRxiv preprint server, Camille Coye, Kai Caspar and Pritty Patel-Grosz describe the dancing they observed and theorize possible reasons for the behavior.

Many types of animals, from birds, to spiders and insects, have been observed engaging in what looks like dancing. And one thing most of them have in common is that the dancing is done by males, generally as a means of attracting a mate. In this new study, the research team has found that adult female gibbons sometimes dance for no other reason than to get attention.

The work by the team began after speaking with gibbon handlers who had reported observing some of their charges dancing in ways they had not seen before. Intrigued, the researchers began studying videos that showed gibbons going about their normal routines, which, the researchers found, sometimes included females dancing.

They noted it was only the females dancing and that they always did it with their backs turned toward an observer. They describe the dances as jerky and robotic, but generally rhythmic, with many of the key elements involved in human dancing.

They also noted that the dances were performed without an obvious purpose, such as attracting a mate. The females would dance for both male and female gibbon observers and also sometimes for other animals, including humans.

The researchers also noted that the dancers would occasionally look over their shoulder as they danced, at the observer, to make sure they were still watching—and that they did it in silence. The style of dancing was also consistent between individuals, though there were variations in duration and sometimes complexity. And it was done by females from four different species of gibbons.

The research trio was unable to identify the reason for the dancing, but suggest it may have something to do with social interaction, or anticipation of an event, such as feeding.