I haven't looked up the details, but I've read that President Franklin Roosevelt's dog, Fala, grieved terribly, and sat by his (FDR) chair constantly. It's said that Fala died of a broken heart.

Hey, I know Logan misses me terribly when I'm gone. John said that even though he's home, it makes no difference. She'll lay with her head on her paws, staring at the door. I'm sure all your dogs do the same.

This story broke my heart. I hate when some researchers say dogs (animals) don't emote like humans. Yeah, right.