Don't they eat everything regardless? I don't think they care.

I don't think they know the difference. When they turn over my garbage can they eat anything and everything and probably have the poops for a week after.

Well at first they just don't know/don't care? what's safe to eat but after they eat something that disagrees with them they would probably stay far away from that after due to experience

According to my Border Collie: "I have no certain time to eat. i can eat anytime, all the time. wave a bone in front and me just watch". This is true, at least with Mikey. when he is really hungry and we have ignored him, he will pick up his bowl and set it in our laps. This dog is too smart.

Dogs can generally tell by the smell of something if food is spoiled or not. If you try to feed a dog bad food they will (typically) try to bury the rotten food. When they can't tell if something is bad or not via smell, they eat it and then throw it up if it's bad (natural reaction, it's not consciously done), and then they won't eat it again. So, it is a mix of genetics (sense of smell, regurgitation), and experience.

I think it has to do with genetics and with smell. They can probably smell something and there is a hint that it is bad for them.

Probably pretty much the same way humans tell. We know that eating things with weird colors or smells can do funny things, so we instinctively stay away from those. We also know what flavors or textures we dislike, and avoid those as well. Dogs use these to distinguish between edible and inedible things, although sometimes they're just dumb and eat poo or something.

It's actually a bit more complex than all of this indicates. There are sick people in the world who will take it upon themselves to poison dogs on occasion. They will often hide the poison in meat. The Meat is good, the Poison is going to kill or make the dog sick..so it is assuredly not safe to eat. Then, we have chocolate. Chocolate is not especially safe or good for dogs. Although almost everyone knows some dog, somewhere, who ate chocolate..perhaps even some insane amount of chocolate....... (my old dog (RIP NOT from chocolate) ate a tray of double chocolate brownies, that he fletched off the table..from way in the back...homemade...with tons of baking chocolate in them...and nothing happened, he didn't even get cannon butt or have elevated heart-rate..zip..zero...zilch).....and nothing happened to THOSE DOGS, known by those people. By the same token, I've seen as many as 8 dogs be rushed into after hours emergency clinics with the toxic aftereffects of consuming chocolate...on any given "high holy chocolate candy" holiday. Some were saved and lived...and others were not, could not be and died. Then we have the dastardly ANTIFREEZE that goes into your car's radiator. It tastes SWEET...why the hell it tastes sweet I have no clue...I with THEY would put something utterly foul into it. Antifreeze KILLS a lot of outside cats and some dogs too...with a fair amount of frequency...it drips, is spilled or overflows... the animals love to lick it up...and it almost always kills them. I hate this! With regards to "bad meat," MOST dogs, if given a chance maybe indifferent to what WE would be willing to call BAD MEAT vs. GOOD MEAT. Meat that has been in a freezer for 1, 3, 5 years... most of us would call BAD MEAT...but NUTRITIONALLY... there is nothing wrong with it. It is likely to be freezer burned and unpalatable to US...but old Spot or Fluffy would be just as likely to scarf it up and wag the entire time! (Because it really isn't "bad" meat!) I know people who feed their CARNIVORES, aka DOGS and CATS freaking ROADKILL...yupper! And it might have been on the road for 24 hours or so...before they pick it up. NOW...I personally am not going to go that far. I might learn how to correctly bleed and butcher out meat, but it isn't currently one of my more developed skills...therefore...I'm not going there. (Plus, I seriously doubt I could LIFT a full grown dead deer into my (as if I would, even if I could) little Saturn car! I think NOT! Some Raw Feeders report that their dog TYPICALLY will take their meat..regular meat not roadkill, and bury it for several days...after burying THAT piece of meat, the dog then moves to another spot and proceeds to DIG UP the hunk of meat he/she buried 2 or 3 days ago and eats THAT ONE NOW! Dogs do not have problems with Salmonella, humans have problems with Salmonella. Dogs will eat COOKED BONES...even though cooked bones ARE NOT GOOD FOR DOGS BECAUSE THEY SPLINTER. RAW BONES (as long as they are not heavy, weight baring bones...like cow, deer, moose, elk LEGS) even RAW chicken bones...ARE not only SAFE...but are healthy for a dog to eat...along with RAW MEAT. The dog doesn't know it...but the correct ratio of species appropriate feed is: 80% RAW MEAT, 10% RAW bone and 10% Raw Organs (hearts are a muscle = meat, NOT an considered an organ when feeding...liver, tripe are both organs) And what about KIBBLE...dry dog food that most dogs will eat...but which is considered poison by most RAW feeders? It's NOT species appropriate food at all. It does not digest well in dogs...compare what "comes out" of a kibble fed dog with one fed exclusively Raw. There is NO comparison. Kibble fed dogs poop more, it smells more...and they poop more often. Raw meat is more fully digested...almost all of it gets used by the dog..so there is less poop...it does not smell as much and the dogs poop less often... there is literally LESS WASTE! Then to top it off...the Raw fed dog poop turns to powder within a couple of days.. poof..gone. So DO DOGS know what is safe or truly good for them? It seems to me they might not...they eat what they are given, what they have access to...and IT might well be something that is harmful to them.