by Whit Gibbons

April 20, 2008

The poison dart frog of South America, scientific name Phyllobates terribilis, is arguably the most dangerous animal in the world. To a laboratory mouse the frog's skin secretions are more than 400 times as toxic as the venom of a king cobra. Another dangerous animal, the funnel-web spider from Sydney, Australia, has venom more toxic than that of an eastern diamondback rattlesnake. Drop for drop, the funnel-web is about five times as venomous as a black widow spider.

The comparative toxicity of 30 of the world's most toxic animals are given in a table in the book "Venomous Animals of the World" (2007, Johns Hopkins University Press) by Steve Backshall. Based on laboratory experiments with mice, the lethal dose measurements are not perfect mimics of how humans would respond, but they are certainly close enough for practical purposes. Whether a deathstalker scorpion of North Africa is 25 or 78 times more toxic than an African gaboon viper won't much matter if you get bitten by one of them. In either case, you could be in trouble.

The book is full of information about and color photographs of the world's most toxic animals. Some are "venomous," meaning they have venom glands and inject the toxin into their victims. Others are "poisonous" in that their bodies or skin secretions are toxic if eaten or otherwise absorbed. The venomous species include scorpions, centipedes, spiders, and jellyfish. Poisonous ones include millipedes that produce cyanide, fire salamanders and California newts with toxic skin secretions, and blister beetles that secrete a burning chemical from their leg joints.

The Sydney funnel-web spider is credited with being the world's most dangerous spider. Although both sexes have venom and will bite, the male is smaller but more dangerous. Interestingly, the venom of male funnel-webs is more virulent to humans and other primates than to mice or dogs, which means that they are even more dangerous to us than some laboratory tests would indicate. Before an antivenin was developed in 1981, at least a dozen deaths had been documented from funnel-web spider bites. To develop the antivenin, venom is extracted from spiders and injected into beagles, which build up an immunity to the spider venom. The antibodies generated by the dogs are the foundation for the antivenin. Apparently the development of an antidote that neutralizes the spider venom in a bite victim has greatly reduced the chance of fatality from the bites.

The book's photography is outstanding, in part because many toxic animals are brightly colored. Some of the photographs include the author himself in situations reminiscent of Steve Irwin, the Crocodile Hunter. In one he is confronting a Mozambique spitting cobra that he says "let rip with a jet of venom, which drenched the goggles protecting my eyes." In another he is holding a brightly colored red, yellow, and black snake "during a tropical downpour," while he is "frantically assessing the colour bands to . . . figure out whether it is a deadly coral snake or a harmless false coral." Backshall is also shown in an underwater scene where he is reaching his hand toward the mouth of a gigantic stingray. He notes that stingrays "generally make excellent swimming partners. I fed this one for nearly an hour and it behaved like a large, friendly dog."

The concluding section of the book discusses some of the environmental threats faced by the featured species of animals. The author notes that unrestrained human population growth, which has now given us more than 6 billion humans, is leading to the decline of wildlife on a worldwide scale. Animals in oceans, forests, and even deserts are under siege from human habitat destruction and other assaults.

"Venomous Animals of the World" sports stunning color photographs of some of the most toxic animals in the world, such as the deadly poison dart frogs with their brilliant reds, yellows, greens, and blues. A first step in any conservation effort is to develop an awareness of and appreciation for all wild animals and plants, even those that protect themselves by defenses that can be lethal to us. This book does just that.

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