Well, last night and this morning the kittens had me very worried. Last night the little one who looks like her mom was panting.
This morning Coda was doing it, and then one of the black ones.
I did quite a bit of research, all of which said panting (without an obvious cause like overexertion) could signal something serious: congenital defect, upper respiratory infection, heart issue. So I called the vet and waited for a call-back. Then I came across something interesting. Someone had posted a video on YouTube showing kittens about the same age, and they were doing what mine were. He talked about how there was a disagreement about whether this was panting – or hissing! He illustrated his conviction that it was hissing, by showing how they did it when he put his finger in front of their nose. Smelling him triggered it, but when he stepped back they stopped. I tried the same thing with mine, and the same thing happened. The adorable little babies are hissing! It seems like panting because it’s prolonged – usually a hiss is a single effort that stops. But they’re doing the best they can to be fierce!
The thing about fostering is that I’m always learning. I hadn’t encountered this before. It’s pretty strange to me that it’s these kittens who hiss, and none of my previous ones have, since their mom is so super friendly. But I’m happy to find out it’s not a major health issue for these little guys.