Large lizards have been important foods since prehistoric times and are still commonly hunted in parts of Asia, Africa, and Latin America.1 Some (such as the monitor lizards seen in markets in Indochina) are carnivorous species that may be difficult to feed and raise economically. However, the iguanas of the Americas offer promise as microlivestock. They are herbivorous and feed primarily on leaves, flowers, and fruits, including many that are too high in the trees to be gathered by man or by other livestock.
Iguana meat is popular throughout much of Latin America, where consumers willingly pay more for it than for fish, poultry, pork, or beef. To fill the demand, several iguana species are hunted by rifle, slingshot, trap, and noose; they are even run down by trained dogs. Villagers (often small children) catch them for food for the family; professional hunters snare and sell them to vendors. Iguanas are hauled around in gunny sacks and wicker baskets by car, boat, horseback, and people on foot. In parts of El Salvador they have been known to arrive at the market by the truckload.
As a result of this indiscriminate hunting, iguanas are now steadily becoming more scarce, and the destruction of their habitat makes the situation even worse. At present, many parts of Latin America's tropical forests are being cleared. The green iguana in particular depends on trees, and as forests disappear its populations are destroyed.
However, iguanas are forest-edge species: they will grow well on ranches and farms as long as patches of trees are left standing. This offers the hope that they can be raised as microlivestock. They reproduce so prolifically that, in principle, populations can build up exponentially. Mature females, for example, may produce 30 or more eggs a year for up to 10 years.
In the past few years, a notable research program in Panama and Costa Rica (see page 351) has laid the practical foundation for iguana farming. It has artificially incubated and raised thousands of green iguana hatchlings. With less than half a square meter of living space per animal, the hatchlings have grown as fast or faster than their wild counterparts. Unlike their kin in the wild - which in their first year of life suffer 95 percent mortality from birds, snakes, and other predators the captive-raised iguanas show almost 100 percent survival. This research project demonstrates that ranching iguanas both for food or for repopulating depleted habitats is feasible. In addition, experimental projects for farming green iguanas have begun in Curacao and El Salvador.
As livestock, lizards have advantages. Being cold-blooded they do not carry human diseases (except for those such as salmonella that result from gross mismanagement). They can be kept in captivity in fairly high densities without diseases breaking out. Although often aggressive in the wild, they coexist in dense populations with few problems as long as they are well fed.
There is an important conservation component as well. Farming these lizards may help check and may even reverse the downward trends of their populations by allowing large numbers to be released back to the wild at a size that inhibits predators.
There are three alternatives for utilizing iguanas:
- To manage wild stocks as game animals;
- To raise iguanas on farms, like chickens and pigs; or
- To raise young iguanas in captivity and then release them into the wild where they can grow to full size and later be harvested on a sustainable basis.
Although the green iguana has so far received the most attention, two other Latin American species are in farming trials. Black iguanas (garrobos) are being raised experimentally in El Salvador and Costa Rica. And the omnivorous tegu lizard, which produces a valuable leather, is beginning to be farmed in Argentina and is briefly described opposite. Both iguana species are described in the following chapters.
The tegus (Tupinambis rufescens and T. teguixin) are large lizards of South America. They are highly prized for their skins, which are made into leather for handbags and similar items. Tegus are heavily exploited; on average, Argentina exports over one million skins a year - about $15 million worth. The 50-year-old tegu industry is estimated to support as many as 30,000 people, including tannery employees and people in rural areas who hunt the lizards full- or part-time. Poor agricultural conditions make farming difficult in the Chaco, and sale of a single tegu skin is worth more than a day's wages for a farmband. Some families also eat the tegu meat and use the fat for medicinal purposes. In many areas, the populations have already been driven to the verge of extinction. Husbandry, therefore, could be beneficial. Traders are hoping that captive operations run by families can eventually replace hunting.
Although usually associated with the arid regions of northern Argentina and Paraguay, the tegu's range actually covers much of South America - as far north as Colombia, including Trinidad and the Amazon basin. One species (T. rufescens) normally occurs in a dryland habitat, such as Argentina's Chaco region. It can occur in great numbers in pastures, probably because of the insects associated with cattle. But it also occurs in areas that are unsuitable for cattle. Some places where tegus are common are so dry that they can carry only a single cow in 10 hectares. There, farmers might find it profitable to raise tegus. This would maintain the native biological diversity while perhaps reducing the soil degradation that cattle cause.
The other species (T. tegubixin) occurs in wet forests, such as those found in Argentina's Formosa Province.
Tegus are scientifically interesting. Little is known about their biology, and basic studies are needed. They are not much eaten, but in some areas the tail is considered a delicacy. Indeed, deteriorating economic conditions are already making them more important as a food resource. Convincing campesinos that they can increase their cash income and their meat production by rationally exploiting these large lizards should not be difficult.
Sustainable exploitation could also benefit tegu conservation. Large populations still exist in some areas in Argentina and Paraguay, but, overall, the species are declining. A welldesigned management project could ensure the maintenance and reestablishment of large populations where numbers have drastically decreased.