Do dogs get headaches?

I believe so, and here’s why. Ever since our dog was a puppy, one of us would take her for a walk nearly every night. Most days she is enthusiastic and seemingly very happy on our walk around the village. Occasionally however, she makes it clear via her body language that she doesn’t want to be out and about. Granted, she is a black, long-haired dog, so I can understand if it’s a hot day and she’s in the sun. But sometimes, it’s on a day which seems to be the perfect temperature for her. She’ll walk about a block at a really slow pace with a really depressed body position (tail down and not wagging, ears and head lowered). Sometimes she’ll actually turn around so she’s facing home and sit down as if to say she’s not going any further. I have thought that perhaps she gets sore muscles, like we would if we ran without conditioning ourselves first, but her activity levels are very consistent (long, slow walks – nothing very strenuous). I have to believe a headache would be the most likely explanation. Physiologically speaking, I can’t see why dogs wouldn’t get headaches. Sure wish they could talk sometimes!!