I have a nice, good tempered 14 year old male unneutered mixed terrier. On many, though not all evenings, starting at about 9pm and going till midnight or even later (last night 4:30am), he will just bark. Bark at a window. Bark at the door. Bark at nothing. I take him out around the block–he comes in and barks. I give him food and water, which may help temporarily, but then he barks.
Again, it’s not every night–about 1/2–but it’s ONLY at night. I’ve tried leaving lights on in case he doesn’t like the dark now.
Often the barking is accompanied with some panting and a bit of "wild eyed" look–I think he may be catching the scent of a dog outside, because he’ s most interested in "sniffing" when I do take him out. BUT–why only at night?
Now, of course, I’m bleary eyed, and he’s sleeping soundly and snoring in the living room!