When one of my cat doesn't used her litter tray at night?

[Harvey]

This started out as a new behaviour for one of my female cats. She used to make use of her litter tray all the time but I'm not sure what happened in the past month for her to stop using her litter tray at night. It's not like the litter tray is dirty because I make sure to keep it clean at all times.

What could be the cause of this new behaviour?

 

[Foxybananas]

Maybe her bladder is weaker and she can't hold it? Is she using it in the daytime? If so, maybe she's too tired to make it to the litter box at night.

 

[Shortie]

This could be several things that could be causing this. Is she too tired to get to that specific litter tray?

Could she have been spooked when using that specific litter tray and now she associates that litter tray and it's position with that fear?

 

[Ragnarok]

I think there is a problem that is making your cat not to make use of the litter box at night. It's either something is scaring it not to go to the box at night which is why is no longer she's no longer doing it. You need to look into this to find out exactly what is wrong.

 

[Sarah]

You can bring the litter box closer to them while they sleep. Maybe she's not really pressed at night, the main reason for not using it. You can observe more and know where the problem is coming from.