Randomly hissing 1-2 month old?

[SamsonizeMe]

I have a baby, (~10 grams) that is showing a strange behavior I haven't seen before. She is randomly hissing when she is under cover or in a hide. She does this when there is nothing perturbing her, whether or not her tank-mates are around her or not. The first time I heard it she was in a hide with another, who was resting on her but not showing any signs of aggression.

My girlfriend and I had the other two, slightly older (2-3 monthers, 15 and 18 grams) both out of the tank, and the baby was alone in a cave hide, and started making the hissing noise twice. When we take the hide off of her, she stops. Another time she was under a log and making the noise. It doesn't seem to matter what's going on. She seems healthy otherwise. Is this a territorial announcement or something else?

Other thoughts: she is an enigma, with no visible enigma syndrome, and she is eating/pooing fine. Girlfriend just checked on her and she was doing it again. The baby heard her talking and stopped.

EDIT:

In case anyone's interested, I posted up pictures of these little ones. Stable for 4! The girls are the ones doing the hissing.

 

[TranceZ]

That's really strange

 

[im faster]

Maybe she is seeing her reflection or something small that your not noticing that scares her

 

[Jordan]

she may be stretching, yawning, waking up, in pain, ill, or just stressed.

 

[SamsonizeMe]

I noticed the other female doing it too when I took the rest out of the tank. The hide is over the UTH, and could be trapping heat a bit. Since they have only been in the set-up for three days, they may simply not realize they can leave that side for the cool side.

Could this be an announcement of discomfort, in that they are too hot?
I will put the thermometer inside the hide and see how hot it gets in there...

 

[bettafish]

Oo, good theory!

 

[SamsonizeMe]

Discovered that it's actually the UTH making this noise. Gonna send it back for a replacement.