it's the same as sam leong sniffing scrooby's butt...haha...lol...
http://www.huffingtonpost.com/2014/07/28/why-do-dogs-sniff-each-others-butts-video_n_5627304.html
http://www.huffingtonpost.com/2014/07/28/why-do-dogs-sniff-each-others-butts-video_n_5627304.html