These are three of my furbabies. The black and white one is Hades and peeking out right under him is Ares and on the left was Jasper. I lost Jasper earlier this year and I still miss him. I have two old rats right now, Hades and Ares are both 3 years old and the average life span of a rat is between 3-4 years, so my boys are old men.
I wrote an article on caring for older rats that you can find here. So many of my friends who have rats have lost their pets to old age here recently and it makes me sad to realize that my boys are getting older and probably won't be around to many more years. Both Hades and Ares are in good health and are spoiled rotten. Healthy rats are always good when they start getting older.
Of course they have slowed down quite a bit, but that's to be expected in older male rats because male rats are known to be much lazier than female rats. Male rats are known as lap rats or cuddle rats because they usually love cuddles and just laying around on you, in your lap or next to you on the couch.
Hades likes to come out and sit with us but Ares has always been a bit more stand offish. Ares would rather you give him a little pet while he's inside his cage, then give him a treat and be on your way. lol
Taking care of an older rat or any animal is pretty much the same. You make sure they are comfortable, healthy as possible, not in pain, and that they can get to their beds, food, water with ease.
My boys cage is a two story and they have to walk up a ramp in order to get to the second story and while they do it more slowly than they did when they were younger, they can still make it up the ramp when they want to, so for now It'll stay in the cage. If at anytime they become wobbly while walking, I will take the ramp out and make sure everything is on the bottom. Right now I have two water bottles in the cage so they can get a drink whether they are on the top or the bottom and a soft bed on both floors.
As pet parents it's our job to make sure our fur babies are comfortable when they get older.