New pooping behavior

So I have a ferret who is about 4 years old and he has recently started pooping all over the shelves of his cage. I have no idea why he started to do it. I tried completely cleaning his cage out and scrubbing it completely and that didnt work. 
 
About three months ago I had to put down my other ferret who he shared a cage with because he had cancer. Could it be that my ferret is now acting out because he is lonely? 

Any idea on what I should do?