My dog is 16 years old and in good health. She sleeps with me in my bed and usually sleeps through the night. Last night she woke me up with yelping and whimpering like she was hurt. I picked her up and cuddled her and she urinated while she was in my arms. This was the most bizarre thing, she’s never done anything like this before. After a few minutes of comforting her she seemed fine. I cleaned up and we got back into bed. She immediately fell asleep again. I fell back asleep too and when we woke up she was her normal self. There have been no changes to her routine nor has there been any type of stress for her. Could this have been a bad dream? 
Dogs clearly dream regularly – anyone who’s ever watched a dog sleep on a regular basis has seen it’running’ in its sleep, and perhaps other behaviors mimicked in sleeping. (Obviously the dogs cannot relate the contents of their dreams, but it’s easily interpreted from the observed behavior.) I see no reason why a nightmare would be exempt from this phenomenon.
Since it’s well known that animals do dream (just another link from quick googling), wouldn’t it be quite surprising if they never had nightmares? Happy your dog got over it though.
I knew a standard poodle that clearly had nightmares even to the point of night terrors sometimes. He would just lay there sleeping and become obviously disturbed from what he was dreaming. If it got bad enough, he would sort of wake up, panic, jump to his feet and bark randomly until he got his composure back which might take a few minutes and then he would be really worked up for a long time after that and couldn’t go back to sleep. He was the most neurotic dog that I have ever known but he was really smart. It was obvious to anyone that saw it what was happening.
FYI, I did know a lady with an older dog that had seizures sometimes where it urinated on itself, so be aware.
But I’ve certainly seen dogs seem to have nightmares - they’re not always having happy chase dreams, I think. Captain more than the other dogs I’ve had has acted fearful while dreaming, and I’m never sure whether to wake him up or not.
I give you: Bizkit the sleepwalking dog.
I’ve had dogs that seemed to experiencing disturbing dreams (accompanied by shaking/agitated motions/barking) and have stroked them gently to comfort them. A few times they’ve awakened at this point. You’d think there might be confusion or a startled reaction, but all I ever got was a look (the canine equivalent of “Meh”), maybe a stretch and a yawn and that was it.
Not even a hint of resentment either (“I was just about to catch and eat a juicy ten-pound steak when you woke me!”).
Why is this considered easily interpreted? I dream about walking and talking all the time, but I’ve never been observed walking or talking while dreaming.
I wonder if the dogs must consciously be understanding the difference between dreaming and sleeping, and that it’s evidence of their intelligence. Hell, that’s not something necessarily all humans are good at (cue women who get dreams about their boyfriends cheating and then are pissed at the boyfriend the whole day).
I generally don’t wake up my dog when he’s having a bad dream. I figure when I wake up during mine I remember it much better vs just sleeping through it.
This has been my experience too. You’d think that if he’d been woken up in the middle of an actual dream, there’d be some sign of confusion. (“Wait, wasn’t I in the middle of a field chasing rabbits? How’d I end up back in the house? Damn.”) So I’m kind of leaning toward believing it’s some kind of myoclonus.
But he even barks when he sleeps! Surely he must think he’s chasing something. Except my dog rarely barks when he’s awake, and certainly not when he’s chasing a rabbit. Humans’ myoclonic jerks, however, are sometimes accompanied by grunts.
I wonder about this, too. I have a 6 month old puppy who has had a few dreams bad enough that he wakes up and runs. Once he was asleep in his crate and ran out snarling and growling like he was in a dog fight. It was a little scary because he had never made those sounds when he is awake (he loves other dogs and AFAIK has never been in a fight) and I wonder if it was because he had run into a dog that day that had snapped at him?
Because when dogs dream, it is easily observed - they (and my data sample is the admittedly small sample of 6 dogs I’ve had throughout my life) regularly twitch and make little ruffing sounds - the same movements and noises they make when running and barking, only muted by sleep.
Dogs seem to have two dream types - what my family calls “the good dream” and “the bad dream”. We like to speculate that in the former they’re chasing something, in the latter it’s the other way around.
No, dogs don’t have nightmares; they don’t even dream. The moment they fall asleep it is just like putting your computer on stand-by. Or so some would have us believe.
Perhaps the more interesting question is why it’s so important to some people to deny what is easily observed (and, according to the link above, was proved scientifically in 2001, if not earlier).