Guinea pig making strange (new) noise

[bluetrooth]

I have two guinea pigs (boys, father and son) and for over two years now there haven't been any issues, but in the last week on two separate occasions, one of them has started making a noise I've never heard either of them make before. He only ever does it at night, and when we wake up to check on him, he's at his (full) food bowl, seemingly fine. I recorded the noise last night. Does anyone here know what this means? Should I be worried?

I've uploaded the recording here, the sound gets clearer around 15 seconds in:
Vocaroo | Online voice recorder

 

[lucifermp3]

I have two guinea pigs (boys, father and son) and for over two years now there haven't been any issues, but in the last week on two separate occasions, one of them has started making a noise I've never heard either of them make before. He only ever does it at night, and when we wake up to check on him, he's at his (full) food bowl, seemingly fine. I recorded the noise last night. Does anyone here know what this means? Should I be worried?

I've uploaded the recording here, the sound gets clearer around 15 seconds in:
Vocaroo | Online voice recorder

That sounds like chirping! Here’s a video for comparison:

It’s a vocalization that wild guinea pigs make, but our domestic friends don’t make very often at all.

The reason behind it is not 100% agreed upon (a quick google search will tell you this much!); in the wild, it could be a “warning” signal for the rest of the herd because the piggy has spotted a predator, so it could be that your boy feels threatened for some reason. In domestic guinea pigs, it seems as though it’s generally the more nervous/anxious ones that chirp. I had a very anxious girl years ago who would chirp on occasion if she saw my parents’ dog, and once she had gone blind, if she couldn’t find her friends because they were on the other side of an L-shaped cage.

 

[Tnoz]

It sounds like you got a bird in cage, when you say full bowl, what was in that?

 

[bluetrooth]

Thanks! Seems to be chirping indeed. Not sure why, but that's definitely the sound he's making.