Age and sex differences, reproduction, and conservation of Iguana iguana
Milwaukee Public Museum Contributions in Biology and Geology
1977
Journal Article
13
1-21
Iguana iguana
The iguana (Iguana iguana), formerly abundant in forest and stream-side habitats of the Neotropical region, is undergoing rapid reduction in numbers over much of its range as a result of overhunting. Sex ratio is approximately 1:1 in observed samples, but males are larger, 110% of female length. Average adult males, of those observed, weigh approximately 1.31 kg and females approximately 1.05 kg. Egg-laying extends over several weeks, with a peak in late February. There is a single annual clutch averaging 30.5 eggs (n = 31). Primiparous two-year-old females are about two-thirds the length of older adults and produce less than one-third as many eggs per clutch (13.4 vs. 44.5). Relative clutch weight increases from about 22% of body weight in primiparae to nearly 28% in old adults, in those sampled, and the eggs of primiparae are small, only 7.4 per cent of large adults' egg weights. As a result, there is a wide range in hatchling size, and the small hatchlings primiparae are probably handicapped by their size. Eggs are laid in deep burrows in open places, often in sand of streambanks. Hatching occurs early in the rainy season, in April, May or June. Only adult iguanas are sold for food in city marketplaces. The sample of 343 measured seemed to fall in about five fairly well-defined size groups, representing discrete annual age groups of iguanas in their second to sixth year. The thousands of iguanas captured by professional hunters and sold in city markets represent only a small part of the harvest; many more are hunted for the pot by campesinos who depend on them to supplement a meager subsistence. Gravid females are especially sought, as the eggs are considered delicacies and are preferred over the flesh. Much needless cruelty is involved in the iguana traffic, which involves prolonged deprivation from food and water, pulling out and tying tendons of toes, sewing shut mouths, cramming masses of trussed animals into crowded containers so that suffocation occurs, and leaving the immobilized animals lying in sunshine to die from overheating. Education, indoctrination and legislation are needed to overcome traditional attitudes and customs of wanton exploitation. There must be sufficient protection of gravid females to assure that eggs will be laid to replace the iguanas harvested. Closed seasons and protected breeding areas are essential. Supplementing protection of natural populations, programs to "farm" iguanas in enclosures providing natural food and other essential resources, and/or to propagate them in confinement for large scale production of young to be used for restocking, have some promise.