system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do dogs have to sniff all over the god's green earth before finally feeling satisfied enough to piss or shit? What are they sniffing for?

It seems like it should be a territorial thing, but this idea seems to fail to me for two ideas: 
1. It'll often take 5-10 minutes of sniffing for my dog to take a shit anywhere--including the same backyard he's been shitting in for over 10 years.
2. Since when is poop a territorial marker? I could definitely be wrong about that one, but it's something I've genuinely never heard of before.
gpt
Dogs shit in about the same way you surf for porn. They will find a spot that they want to mark to keep other animals away, then they smell a spot where a bitch just did her business. The dog will then look for a spot marked by a bitch and also a pest droppings nearby. The dog finds a good spot, then thinks there must be something better. Again continues surfing until a spot is found that can be marked and get the attention it deserves.