Your best rat or mouse isn't necessarily a fat one she says Raising rodents can be a dicey business

"Your best rat or mouse isn't necessarily a fat one," she says Raising rodents can be a dicey business. They won't mate if the air-conditioning is too high; yet if they get too hot, they die. Tippie's rats stay lean on a high-fibre diet that includes beet pulp and wheatgerm, which means they make healthier reptile food. "It's like someone who wants the best for their Mercedes," she explains. "They don't want junk parts." And predators can be picky: the more delicate reptiles are only able to digest the "pinks" (newborn rodents) and the "fuzzies" (those about 10 days to three weeks old). A large adult rodent, served alive, may gnaw a snake to death.While some buyers are willing to take frozen rats, which can be stockpiled, shipping costs often make them more expensive than the live ones.

Besides which, many reptiles insist on a live or freshly killed meal. "You can train them to eat thawed-out frozen, but some owners won't take the time," says Toby Cromwell, a herpetologist at Reptile World Serpentarium near Orlando. Anyway, he says, many reptile owners love watching the attack. "The snakes don't need that, but it fascinates a lot of people."At the moment, evidently, a wave of so-called "power feeding" of reptiles is adding to the shortage. This means giving them two or more rodents a week, which encourages fast growth "People are 'bulking up' their snakes and lizards. It's an image thing," says David Tetzlaff, an animal curator at Caribbean Gardens, a tourist attraction in Naples, Florida. "I've seen monitor lizards so overfed they look like footballs with legs." The sad truth is that small lizards and snakes just don't impress any more.

The promotional slogan for the 1998 remake of Godzilla has embedded itself in the psyche of many a reptile fan: "Size does matter". James Murphy, a herpetologist at the National Zoological Park in Washington, DC, says that these days he can easily distinguish between pythons or boas that have been reared in captivity and those found in the wild. "The captive- bred ones have bodies so big that the heads can't keep up with them." Never mind the rodents: all this eating can mean an unhappy end for the reptiles. David Tetzlaff delivers a gory warning about the risk of "hair impaction", which afflicted one of his monitor lizards last year. Too many rat snacks, he says, caused the creature "to form a hairball the size of an orange in its gut. A vet had to perform emergency surgery."Working at a breeding centre is, according to many, a revolting profession. "It's filthy - and then there's the smell," says Susan Tippie.

Her worker turnover rate is almost 100 per cent a year: "Some people quit during their first coffee-break."She is careful, she says, not to rear animals that are too ferocious, putting down "the biters" with gas - "because biters breed biters". She herself has been bitten a fair few times in her eight years in the rat- and-mouse business, and the leather gloves she wears to work show the wear-and-tear of daily nibbling.Paradoxically, in the midst of this surge in demand, some rodent breeders still haven't made much profit. "I heard there's a fortune in rats, but I haven't seen it," says Jim Dykes. "I sold about $100,000-worth of prey mammals last year, but I'm living on noodle soup.

In fact, the rats eat better than I do."Many new breeders make critical mistakes, such as keeping the thermostats in their breeding buildings at too low a setting, which can mean that they wipe out much of their stock overnight That is what happened to Jim Dykes. One night last spring he allowed the temperature in his mouse building to fall and remain for several hours below the 70F at which the creatures thrive. He had forgotten to turn off a huge fan that helps to cool the building during the day: mice and rats often stop breeding if the temperature exceeds 80F.The result: "Most of them died and our production of mice dropped to 400 from 4,000 a week." The financial disaster was compounded because, to keep his regular customers happy, Jim Dykes was forced to buy mice at retail on the open market to meet his orders "So I got stuck as a buyer in a seller's market," he shrugs. In addition, he is beleaguered by buyers striking a hard bargain. "They'll call you up and say, '40 cents for a mouse? I can get them for 25 in California.' But when I ask them why they don't buy them in California, they say their breeder doesn't have any.