Can someone explain to me why Cooper's butt smells so bad at night? Not during the day, just at night. Usually after she licks her own butt. (She's a dog.) I wonder if her anal sacs need to be expressed. I read about that once, only wouldn't she then smell bad in the day too? Maybe there's some cross-reactivity between her saliva and her butt effluent that's making her butt stink, and we only really notice it in the evening because she doesn't lick her butt during the day. Or, more likely, we're just less likely to be around during the day. Either way, it (the mystery source, her anus/mouth) smells like a swamp. A swamp filled with feces.