Quote Originally Posted by Dalek Supreme D L View Post
Not being a dog or knowing much about dogs.... I really don't know what the bum sniffing thing is about(surely dog sent/roaming/hunting land marking is via urine not shit).....at least humans don't have to grab each other via the throats or role onto our backs....or do we Being a Dalek its all about the colour of the case work
But with dogs it's not just about urine and faecal matter.........they have a little something extra of their own:

Whenever your dog urinates or defecates, the anal glands receive a small amount of pressure, and a tiny bit of the fluid is released, along with your dog's custom blended scent. Your dog can also express a little of his personal essence when he meets a fellow canine. Have you ever noticed that when two dogs meet, they often raise their tails on high alert? This action applies the pressure to the dog anal glands, and this leads to the traditional butt sniffing we humans cannot seem to fathom. However, to our dogs this behavior is as normal as shaking hands when you meet someone new. By sniffing, the dogs learn to identify each other by their scents. Equate it with exchanging business cards, and you have the idea.

If you're alarmed at this point about all this expressing going on, don't be. Remember that a dog's sense of smell is light years beyond our own, so the amount of the actual expressions are minute, and you'll likely never smell anything yourself unless your dog develops an anal gland infection.

http://dogs.lovetoknow.com/wiki/Dog_Anal_Glands

(Ha-ha, I bet you didn't think this thread was gonna go in this direction when you were typing the original post, did you!!!?)