"There are some frogs that you have to simulate rain for or they won't come out and breed," Wiese said. "Other frogs, they just need to hear the sound of rain and the sound of lightening and thunder. That's what sets off their hormones."

Around since the 1980s in paperback form, most of today's studbooks are in computerized databases. Basic information such as family tree, medical history, age and weight are entered by studbook keepers, then sent to a central location where the data is analyzed and converted into a "master plan" for breeding.

But the databases have their limitations. They aren't updated quickly and don't include the extra information from the dog-eared husbandry manuals on setting the optimal conditions for an animal's breeding.

So zookeepers who rely on the databases might not know, for instance, that satanic leaf-tailed geckos like group sex, that fighting equals foreplay for giant leaf-tailed geckos or that expectant gecko moms should eat snails.

That could mean the difference between a sustainable population and extinction of a species, said Ed Diebold, director of animal collections at Riverbanks Zoo, one of the only zoos to successfully breed several species of geckos.

"Big populations out in the wild breed randomly," Diebold said. "In captivity, usually these populations are considerably smaller than wild populations, which is why you can't afford to allow animals to inbreed or breed along closely related lines. That's why you have the studbooks."

Careful planning among zoos may take some of the wild out of "the wild thing" but it also ensures that the most genetically diverse animals breed, said Steve Feldman, spokesman for the Association of Zoos and Aquarium, which oversees all studbooks.