The Antifragile Chaos Monkey
Man, now you've got me examining stool samples?I would guess that they are from either a scavenging dog (small or medium-sized) or from a raccoon. The reason is the consistency (long and firm, or in cylindrical chunks), that they both have similar digestive tracts, as well as the variation in color (both animals tend to have a varied diet that results in these color variations). Also, both animals are quite territorial with regard to their bowel movements in that they will continue to poo in the same general area until there is reason not to. I can't really be certain unless I am able to smell it. Raccoon poo is very distinctive, making it easily identifiable. Dogs also have a distinctive smell to their poo, but not nearly as much as raccoon poo.
Actually, I'm going to go with a raccoon, because dogs don't generally move much when they poo, whereas raccoons do.
I swear my dog walks like 10-20 feet while doing one poo. It's comical. Well, except that we have to scoop it.
Andy I'm leaning racoon:1) These were small (you guys couldn't tell from the photo!) and2) There aren't many dogs likely to be in my yard: I am close to only one house, and there dog is always fenced in.