Flying By

A key ability for survival is the recognition of the motion of objects. If you’re an animal that may become lunch you certainly want to take good care that nothing is sneaking up on you. Lying about in the sunshine watching gives you plenty of warning as any movement out there will attract your attention.

This is where Zabala et al start off in their recent paper in Current Biology (1). Needless to say that’s not where they finish as they pondered over the problem of detecting something moving when you are in motion as static objects come into view, pass by and disappear as you march onwards.

Specifically, they pondered on flies. It is notoriously difficult to sneak up on a fly and they asked the question would it be easier if the fly was also moving. To put this too the test, they built a fly-sized robot that could move around with a fly without dominating the visual space, so it would resemble a predator as opposed to you or I with a copy of the Sunday newspaper in a tight roll.

They tried this out with female flies walking around, no flying by in this case as they wanted the robot to be more interesting than a passing tourist and more like a predator or a promising version of a fly-lothario.

If the robot was static, the female flies ignored it as though it were part of the furniture. The habit of predators is to sneak up from behind and when the robot played that role, the females froze until they knew if they were going to be eaten or ravaged. Of course, with the robot, ravaging wasn’t on the menu, and none of the flies were de-briefed during or after the experiment.

It is interesting that we tend to react the same way. As I was walking this morning my senses went onto high alert when I heard or spotted anyone out of the corner of my eye beginning to catch up. Having been fine-tuned by this report, I became keenly aware that a couple of different females paused as I caught them up and waited for me to pass. I didn’t ask if they thought that predation or ravagement were on the program.


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