I rescued my old rat Mendez from a shelter a little over a year ago and he's hitting around 2 years of age. Lately he's been showing some worrying signs. A lot of lethargy; he won't move from a level in the cage for nearly an entire day. He's lost a lot of weight suddenly and his sides are sunken in along with constant quick breathing. My poor babe can hardly move a few inches without keeling over from exhaustion. I'm thinking about getting him put down, since he's obviously miserable. What does anyone else think?