Rat on a diet
scroll down to
the rat cabin,http://www.martinscages.com/images/full/...
the rat lodge http://www.martinscages.com/images/full/...
or the rat retreat http://www.martinscages.com/images/full/...
they have shelves and levels to exercise and flex his feet and a solid bottom too and are no bigger than a decent tank
they would certainly encourage climbing and exercising, allow hammocks to be hung, allowing him to be off his feet to rest etc
please try him, for his sake
OH AND BY THE WAY
he still needs a same sex friend as well, a friend would help him exercise, keep him playful, less stressed
AND
help him get over his fears which are solely caused by having no other rat to let him know things are A-OK, rats, being neophobic, rely on each other to help them over come those phobias. us as humans just dont do it for them ; - )
with a friend the smallest cage I WOULD recommend would be the
rat high rise [H 600HR]
http://www.martinscages.com/images/full/...
hope that helps