What a nice picture!
I am not an expert in caterpillars, so I had to ask for help with this one. (Thanks Dave!) This is a Tobacco Hornworm (manduca sexta). I thought it was a tomato hornworm, but what do I know? They are often confused. Like most caterpillars, it's main job is to eat! Tobacco hornworms feed on tomato, tobacco and Jimson weed leaves.
My expert friend says that your dogs probably won't have much interest in eating these because they can taste bad. I didn't ask him how he knew that. The hornworm can get your pets sick, if it has been eating a toxic plant like Jimson weed (also known as stink weed). However, most likely your dog would spit it out before swallowing it because of the bad tasted.
