Cocoa Mulch Can Pose Risk for Pets
Cocoa Mulch, which is sold by Garden supply stores, contains an ingredient called 'Theobromine'. It is lethal to dogs and cats. It smells like chocolate and attracts pets.
Theobromine is in all chocolate, especially dark or baker's chocolate which is toxic to dogs. Cocoa bean shells contain potentially toxic quantities of theobromine, a xanthine compound similar in effects to caffeine and theophylline. A dog that ingested a lethal quantity of garden mulch made from cacao bean shells developed severe convulsions and died 17 hours later. Analysis of the stomach contents and the ingested cocoa bean shells revealed the presence of lethal amounts of theobromine.
See http://www.snopes.com/critters/crusader/cocoamulch.asp for more information.