Chocolate is poisonous to dogs. Have you ever wondered why?
The following link from webmd explains:
The breakdown below shows us that cocoa (chocolate) contains theobromine and caffeine which are hazardous to your dog’s (pet’s) health and can kill them. Some dog treat manufacturers use carob, a healthier substitute for animals.
Also, beware of cocoa shell mulch in your own yard or other yards you pet may venture into. It is toxic to animals. Cocoa mulch is made from the cacao shells which contain theobromine.