Companion Dogs

Absolutely.  They go through a grieving process, I've seen it within my own dogs.  They do move on, but I've observed "sadness" and I've observed my dogs searching for the deceased dog.  

It may sound funny, but my dogs understand what "all gone" means which I use when there is no more of something, i.e., food or treat, whatever.   When my Codycoe died last summer, Buddy grieved hard (he's such a beautiful soul).  He would look for her around the yard and I would say "Cody all gone".  He would look at me with his big sad eyes, then come lay down by me with a big sigh.

Yes, they grieve.

Absolutely.... It is beyond sad to watch a dog without their companion. When Jasmine's mate Bo passed away in '06, she was devastated.  Thankfully the Raptors were born at the end of the month. She buckled down to help with the pups. Had it not been for them we would have been in trouble.

Earlier in our kennel  we would get a pup to not replace, but to occupy the dog remaining. It gave us many more years with each of our older dogs.

Bonita of Bwana

For certain.  And one dog knows when the other dog is sick.  What a sad experience to see sister littermates having to say good bye to one another.

Here is a my thread and what I did to help bring back the surviving pup. 

http://community.dog.com/forums/t/70012.aspx

They certainly do.  Not only dogs but cats as well.  My SIL had to put down one of her littermate Cat's at 15 years old, one full month ago and the remaining litermate meows tiredlessly all day and night and she can't seem to make him happy.