'Death by Chocolate' : Wild Dogs controlled by chocolate

While humans happily stuff themselves with chocolate at Easter and Christmas, the confection contains chemicals that are lethal to many animals.

Dogs are especially vulnerable. Just 240g of unsweetened dark chocolate can kill a 40kg dog the size of a german shepherd.

While some scientists have focused on the healthy antioxidant properties of chocolate, others are looking into its darker side, it was reported yesterday.

American experts are testing a mixture of caffeine and the chemical theobromine, both found in chocolate, to see if it can be used to control coyotes.

The wild dogs are serious pests in the US, killing $25 million worth of livestock each year, damaging property and attacking people and pets.

Fences are ineffective against them, and poisons such as sodium cyanide are toxic to people and other animals.

The chocolate poison under investigation kills coyotes quickly and with minimal distress, and is harmless to humans.

Chemist John Johnston, from the US Department of Agriculture, who is leading the research, told New Scientist magazine: "If we can come up with something that is more selective, it offers an advantage. It's a more responsible approach."

Cocoa beans, from which chocolate is made, are naturally rich in caffeine and its chemical relatives theobromine and theophylline.

Humans tolerate chocolate mainly because of the speed at which their bodies break down theobromine.

Rats metabolise it much more slowly, and dogs more slowly still. An average adult would have to eat about 50kg of chocolate at one sitting to consume a lethal dose