Dogs Don't Cry

This dog is supposed to be showing "tears of gratitude" after being rescued along with her puppies: 

Is this likely? I mean, I’d cry too if I were covered in demanding puppies and some dude shoved a camera in my face. But…biology says nope. Normally a dog’s tear ducts drain into the mouth, not down the faces. Even if they did cry when they were sad, we’d never notice, and all they’d get would be a mouthful of saline. 

The only reason a dog would have watery eyes - a condition called epiphora - is if there’s something medically wrong. Usually epiphora is caused by a something irritating the eye and blocking the tear ducts, whether that’s a foreign body, allergies, or an underlying medical condition like entropion.