My boys and girls both have a chinchilla Townhome. My boys have three shelves in their cage, my girls have two. I introduced the both pairs to perches. The girls are always sitting on theirs, and somehow squeezing both of their butts onto a 1 1/2 inch wide, four inch long perch. I have not added the third shelf so they can have room for perches. The boys seem much less interested. They are always on their shelves. Do some chins just have a preference? Or should both be offered?