Over the weekend the doting owner of two young lab mixes
purchased Cocoa Mulch from Target to use in their garden.
They loved the way it smelled and it was advertised to keep
cats away from their garden. Their dog Calypso decided that
the mulch smelled good enough to eat and devoured a large
helping. She vomited a few times which was typical when she
eats something new but wasn’t acting lethargic in any way.
The next day, Mom woke up and took Calypso out for her
morning walk. Half way through the walk, she had a seizure
and died instantly.

Although the mulch had NO warnings printed on the label, upon
further investigation on the company’s website, this product
is HIGHLY toxic to dogs and cats.

Cocoa Mulch is manufactured by Hershey’s, and they claim that
‘It is true that studies have shown that 50% of the dogs that
eat Cocoa Mulch can suffer physical harm to a variety of
degrees (depending on each individual dog). However, 98% of
all dogs won’t eat it.’

This Snopes site gives the following information: 
 http://www.snopes.com/critters/crusader/cocoamulch.asp 

Cocoa Mulch, which is sold by Home Depot, Foreman’s Garden
Supply and other Garden supply stores, contains a lethal
ingredient called ‘Theobromine’. It is lethal to dogs and
cats. It smells like chocolate and it really attracts dogs.
They will ingest this stuff and die. Several deaths already
occurred in the last 2-3 weeks. Just a word of caution, check
what you are using in your gardens and be aware of what your
gardeners are using in your gardens.

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 cacao bean shells revealed
the presence of lethal amounts of theobromine.