nesting

Hi! I have two female rats, in the last week or so one of them has suddenly had a big behaviour change. She is hoarding all the food and has become very territorial - she's taken one of the shelters in the cage as her den and is nesting. She takes all the bedding and will lash out at the other...

While looking on Oxbow's website (to see if their essentials diet for rat was non-GMO or not), I came across that they recommended putting hay in yours rats' cage for nesting material. Is it worth it to spend the money and get them some hay? I saw something on one site saying that the oils found...