So afaik there’s no definitive answer as to why they do it. I heard it’s an attempt to lure prey closer but I find that not very convincing as I can’t believe it would ever actually work, especially since they make the same sound for mice, birds and even insects.

I’ve observed two aspects about it that I haven’t heard anywhere before: They only make the sound when the prey is out of reach and there’s a social aspect to it. I’ve tested both myself. If you want to you can test the social aspect too. Next time your cat is locked in on a bird outside the window just make a vaguely chitter-esque sound and there’s a good chance it will join in. I do it a lot since I’ve discovered it’s contagious for them. Really gets them riled up and ready for murder 😅

My best guess is when cats do this they’re basically stimming, similar to purring. They don’t have naturally great attention spans but they need to stay focused on the prey in case it moves within range. Producing a sound might help them stay in the zone. The fact that it can be triggered by making the same sound does puzzle me a little. Maybe it’s just a way for them to bond, sort of like howling in wolfs. Hunting is very important to them after all so actively stalking prey together could be a way to strenghten the relationship. I don’t think they do it as a hunting strategy though. Maybe I’m wrong but I’ve never seen house cats actually hunt together as a team.

Ok enough yapping out of me. What are your thoughts? Do you have theories of your own? And have you ever chittered together with your cat? 😄