When I want to know what’s your favourite song, I just ask. It’s as simple as that. But how do you ask a fly what’s their favourite song?
Clearly, flies cannot tell me what song they like as a person could, but you can tell what songs flies like from their behaviour. This is because, when flies hear a song they like, they change their behaviour, they actually start to dance and sing along – no kidding. Well it’s a bit more complicated than that as only male flies actually sing along, but both males and females start dancing, or as scientists would say, they increase their locomotor activity and chase one another. But really, moving and chasing is what a dance is, so I will call it dancing.
Flies don’t dance and sing to any song, no, they are picky. For example they don’t sing to Travis’ Sing, sing sing despite the clear encouragement to sing.
Flies only dance to songs that meet certain criteria: they need to be at the right frequency and come in the right rythm. The right frequency and ryhthm are determined by the species the fly belongs to, as fly species sing differently and like their species’ songs most (see my post from the 27. April ’16).
So how do we find out what songs flies like? We need flies, a speaker, fly song for playback, and fly chambers to prevent flies from escaping. You then place flies in the chambers and start playback. If flies like the song they’ll start dancing and females become more willing to copulate (note it’s female flies, not humans).
I am interested to find out whether flies care about variations in volume over time. So I designed fly songs with variations that are typical for three different species: melanogaster, simulans and yakuba. For that I calculated the mean gain for each species, generated an envelope with that gain and masked songs of the three species, as you can see here:
So which of the songs do flies like? I will let you know in the next post.