tortoise
Wild Hare
I think you're right about cotton, unless you have waterproofing spray on hand. Lanolized wool would be best. Cordura nylon and/or polyester fleece would be good choices too.I’ve got a really old hoodie/jacket with a broken zipper and some holes. It think it would fit her but it’s cotton fabric, I’m afraid it would hold more water than her fur and she’d be worse off. We get a lot of rain in the winter usually. There’s no way to stay dry, even though they have shelters someone will always push her out and make her run into another one.
Tip: It costs less to buy fleece blankets at thrift stores than to buy fabric.