33 Green Iguana

FIGURE

As noted, the green iguana (Iguana iguana) is consumed throughout Central America. It is already subject to heavy commercialization and its populations are plummeting. This is not likely to change: as human population increases, so does demand for iguana meat and eggs as well as for live iguanas, thousands of which are kept as house pets.

Because of its herbivorous diet, inoffensive nature, and high reproductive potential, this reptile is a prime species for intensive management. Alert, curious, and social, it is easily tamed from birth. Given minimal protection during the reproductive season, large populations can build up, and animals can be maintained in simple facilities.

However, although iguanas can be maintained as microlivestock, they may require three years to reach market size. Raising them to maturity entirely under captive conditions is thus probably uneconomic at present, when specimens can still be inexpensively (albeit often illegally) harvested from the wild. However, it has been found that if released into the wild, most will remain in nearby trees, especially if people erect simple feeding stations and keep them stocked with table scraps or weedy vegetation. This makes for very low-cost production during the years of waiting.

Given such findings, iguana farming has a promising future. With research, growth rates can undoubtedly be increased and maintenance costs reduced. Also, iguanas are becoming more valuable each year. Even now, farming them could be economic in some areas where wild iguanas are scarce, especially if the young are released into forested sites when they have grown to a size where mortality is low.

Although green iguanas will happily graze pastures, they need trees. Iguana farming, therefore, provides a way to keep tropical forests standing while still providing people with meat and income. By growing lizards, farmers don't have to fell the forests to create space for growing food crops or cattle. Iguana farming thus gives an economic incentive to preserve the beleaguered tracts of remaining trees. It may even render reforestation economically attractive. And it may promote the use of shelterbelts and contour strips of trees in cattle-ranching areas. Today's researchers estimate that 200-300 kg of meat can be produced per year per hectare from iguanas.

APPEARANCE AND SIZE

The green iguana can grow to more than 2 m long, but more than half of that length is in its whiplike tail. Adults of breeding size generally weigh 2-4 kg. The scaly skin is green, yellowish, or golden brown with dark markings; color is a function of age and reproductive stage.

DISTRIBUTION

This large lizard is indigenous to a vast region stretching from Mexico to northern Brazil and Peru, including a number of Caribbean islands. In Mexico, it occurs in tropical forests along both coasts.

STATUS

Green iguanas were formerly abundant throughout Central America, but no longer. In the mangrove forests along Mexico's Pacific coast, for instance, only 5 percent of the former population remains. In Guatemala's Pacific lowlands, mere remnants are left. In El Salvador's jungles, the animals have declined to 1 percent of their former density. And in both Panama and Costa Rica, the species is now officially classified as endangered.

HABITAT AND ENVIRONMENT

The green iguana usually lives near water in tropical lowland forests. It thrives only as long as some trees remain. The forests may be either humid or seasonally dry. The animal normally inhabits the treetops, feeding on tender shoots and fruits in the canopy; few other herbivores can convert such forest foliage into food for humans.

BIOLOGY

Like cattle and other herbivorous mammals, iguanas have a specialized digestive system with an enlarged fermentation chamber in which bacteria break down plant cells. Vegetation is converted into meat about as effectively as in cattle, but not as quickly.

After reaching sexual maturity, at 2 or 3 years of age, females lay one clutch of 10 85 eggs each year. (For most specimens the average is probably about 35.)

Native habitat of the green iguana

BEHAVIOR

The animals are generally slow moving and lethargic when cold, but during the heat of the day they become extremely alert and can run, swim, and climb with speed and agility.

They have a complex social structure and a defined annual reproductive cycle. Hatchlings adapt easily to captivity both when artificially incubated and when captured in the wild. However, captured adults, used to living free, are hard to keep in small enclosures.

USES

Green iguanas are used mainly for food. The meat tastes somewhat like chicken and in Latin America is typically cooked in a spicy stew. The eggs are also consumed. Small and leathery shelled, they are considered special delicacies and are said to cure various ailments.

There is a sizable demand for live iguanas in the international pet trade.

Exploitation has been mainly for the flesh; the skins are wasted in most cases. However, given organized production, green iguana skin could perhaps become a farm by-product. It sells in the international reptile-leather market under the trade name "chameleon lizard." The hide is typically up to 20 cm wide. Thin and relatively fragile, it is glued to a fabric or cowhide backing to prevent it from tearing. The prime uses are for ladies' accessories, belts, wallets, and shoes. It is inappropriate for uses that involve flexure because the scales overlap and repeated flexing causes them to separate. The skin then becomes rough to the touch and loses its glossy finish.

IGUANA MAMA

The program that now offers hope for raising green iguanas as microlivestock is the brainchild of zoologist Dagmar Werner. She began in 1983 by collecting 700 iguana eggs and then learning what to do with them "on the job."

Through a combination of luck and intuition, coupled with determination, she discovered appropriate conditions for incubating the eggs on the first try - no less surprising because her incubators (dirt-filled wooden boxes warmed with light bulbs) were in an apartment in a high-rise building in Panama City. Nonetheless, most of the eggs hatched and the several hundred squirming young lizards were quickly trucked to a forest park near the Panama Canal. Here, for five years, assisted by a steady stream of enthusiastic Panamanian biology students, Wemer experimented with cages, feeds, facilities, breeding genetic selection, and the myriad aspects of management.

These dedicated researchers eventually devised what might be considered a production line, and they hatched and raised tens of thousands of green iguanas, reduced the animals' infant mortality rate, and created the basic underpinnings for economic production.

In 1988, administration for the project was shifted to neighboring Costa Rica, where Werner established another research farm as well as a fund-raising foundation. From there, she hopes to catalyze all Central America to take up iguana production.

Her immediate goal is, paradoxically, to preserve the lizards by putting an iguana in every pot. That will help reduce the indiscriminate hunting that is taking these animals toward extinction in the wild.

Her system is based on setting up feeding stations in the woods and releasing iguanas at seven months, an age at which they are virtually immune to predators. Iguanas need trees, and her ultimate goal is to help save the vanishing rainforests. With profitable iguana farming, she hopes to persuade farmers to save the trees as homes for iguanas, rather than clearing them for crops and cattle.

"Iguana management and an international marketing system will protect, rather than exterminate, the iguana," Werner says. "I don't think iguana farming will stop deforestation. But I do think it will contribute a great deal."

HUSBANDRY

The iguana farming project in Panama and Costa Rica (see sidebar) provides a model for what might be done elsewhere. In its first five years of operation, the project raised more than 10,000 green iguanas.

To create the farms, enclosures are constructed with sheet-metal wails sunk 30 cm in the ground.' Inside, the animals sleep in shelters made of bamboo and vegetation. Each shelter has an adjustable entrance slit through which young lizards can slither, but predators, which usually are larger, cannot. Most are set on stilts and food is served in the shade underneath. With this system, from 20 to 60 young iguanas are kept in an area of 10 mÝ (0.5-0.17 mÝ of land area per individual). In another "high-intensity" design, 30 hatchlings are kept in cages I mÝ in size (only 0.05 mÝ per individual).

The iguana farms also include an artificial nest consisting of a "tunnel" leading to a sand-filled egg-laying chamber. (Both tunnel and chamber are made of concrete blocks or other predator-safe material.) Female iguanas (at least in captivity) prefer this to digging their own tunnels, and it is an important advance in iguana breeding because it produces a hatching success of close to 100 percent. Recent versions require no human intervention: the eggs incubate and hatch by themselves and the hatchlings climb out of the nest through a hollow bamboo "pipe" and fall into plastic bags, which can be easily emptied twice a day.

The iguanas are fed mixtures of broken rice meal, meat meal, bone meal, fish meal, papayas, bananas, mangos, avocados, and a variety of leaves and flowers. Each day they receive fresh-cut leaves from plants such as beans, mustard, or hibiscus. Hatchlings are raised to an age of 6-10 months, when they are big enough to be released into forests, farmland with scattered trees, or into village backyards with almost no vulnerability to predators.

ADVANTAGES

With each female producing an average of 35 eggs annually, these animals have inherently high reproductive potential. And if the young are protected from predators during their first few months, populations can build up rapidly.

Iguanas adapt well to second-growth forest and to backyard conditions and can feed on the leaves of fruit trees or timber trees while the farmer can harvest the fruits or wood. Unless grossly overstocked, they are unlikely to affect the productivity of the trees.

LIMITATIONS

These lizards may take three years to reach marketable size,2 and the cost of raising them to usable size entirely in captivity is currently greater than their market value as food. Less-expensive methods of raising the animals must be found if large-scale commercial iguana farming is to become economically feasible. The main problem is the high cost of the enclosures, not the cost of food. The food costs no more than that for raising a chicken to marketable size, but iguanas do not grow as fast as chickens. For smallholders the only cost of raising them is labor, and that is often unimportant. Free-ranging herbivorous lizards can damage home gardens.

RESEARCH AND CONSERVATION NEEDS

For conservation purposes, the main need is to educate people throughout Latin America to the iguana's plight. For example, in Central America people catch pregnant females and cut out the eggs for food. (There is a widespread misconception that the females survive this brutality.) This is devastating to the iguana populations, yet by installing artificial nests, farmers could let the females live and still harvest the eggs. Moreover, people could eat half the eggs and incubate the other half to repopulate the trees around their farms.

It is also important to develop an understanding of iguana reproduction in the wild. At present, the longevity, growth rate, and age of sexual maturity are not well known. Such information would provide baseline data for creating conservation measures to reverse the depletion of this natural resource.

Further husbandry research is needed. Costs must be reduced. The effectiveness of artificial nests must be tested in village practice. Survival rates of captive-raised young after release must be studied. And harvesting and recruitment schemes should be developed to secure optimum exploitation of the repopulated forests.