In many facilities, reports of succ

In many facilities, reports of successful copulations and fertile eggs are confounded by low hatching rates. It seems that even with fertile eggs, if a female does not nest properly or holds the eggs too long because she is not comfortable with the nesting situation, the majority of the eggs will not hatch. Proper nesting is defined as the female digging a burrow a few days to a few hours before laying, laying the eggs in a relatively timely matter (a few hours, not days), covering the nest, and (often) defending it (Lemm et al., 2005). Other factors potentially contributing to nesting failures include nutrition and incubation practices.

To achieve nesting success, nesting areas should be deep, spacious, and warm (85-87 ° F/29.4-30.6 ° C) with optimal soils. Ideally, the substrate throughout the cage should be at least three feet deep so females may choose to nest in a variety of places. At many facilities, especially off-display areas, this depth of substrate is not possible. In this case, built-in nestboxes, constructed to be as large as possible should be used. At ICR, nestboxes measuring 4’ x 4’ x 3’ high (1.2 m x 1.2 m x 0.9 m) have been used with some success. Further, plastic nestboxes, made from large Rubbermaid or other boxes, have worked for some species. However, these nestboxes are usually only successfully used by young animals or first-time breeders for the first year or two, followed by below-average nesting (J. Lemm, pers. obs.). Indianapolis Zoo has had nesting success with Rubbermaid tubs that are completely buried in sand substrate. Animals enter these tubs by digging down and entering a hole cut in the side of the tub.



Sedgewick County Zoo.
Photo by Veronica Laflin


Nesting boxes work well for young or first-time breeders. The nest has been exposed to show the eggs.




San Diego Zoo. The house is heated by 2 Pearlco ceramic bulbs.

Some institutions have used sand, rich soils, or a mixture of the two with success. Nesting soil should be free of rocks, gravel, and other large debris. Sifted dirt is used at ICR, as it holds moisture that in turn keeps burrows from collapsing. Nests are misted three times a week or whenever they become dry. For pickier nesters, items such as rocks or logs may be necessary for animals to burrow underneath. At ICR, nestboxes are situated in the sunniest corners of each cage. They are usually used to some degree, but on occasion animals choose to lay in the warmer dogloos. To discourage this, plastic pig blankets (Stanfield ) placed on rheostats have been used under the soil. Nests are changed annually depending on how well the animals laid the previous year. Nests may be completely dismantled and reconstructed differently after poor nesting, or left alone after successful nesting. Various types of trashbins, plastic tubs, or soil placed in plastic dogloos have been used, but not as efficiently as the larger nesting areas. Although there has been some success with artificial nesting areas, it is usually in small females. Larger female iguanas rarely lay good eggs or nest well in artifical nesting areas. Indianapolis Zoo reports that their animals usually nest near a heat source and that most tunnels are proximal to heated rocks. At ICR, red lamps have been placed above nesting areas when outdoor temperatures were below average. Every female that was gravid at the time of the low temperatures constructed nests and laid eggs in chambers below the red lamps. In our new facility at the Wild Animal Park, all gravid females have laid in the indoor section of the enclosures, nesting readily in the deep soil.






Captive iguanas will usually guard the nest area after eggs are laid. Both animals in these photos chose to lay in the trash bins, which were located within large nesting areas in the corners of their indoor cages. The eggs have been exposed for the photo (bottom).

On average, smaller females in our facility usually only produce one clutch per year (C. collei, C. lewisi), while some larger females sometimes produce two clutches in a single year (C. n. nubila).
After oviposition, females that have laid fertile eggs often guard the nest. Occasionally those that have laid infertile clutches will guard nests as well, but to a lesser degree. In most species it is easy to tell when a female has laid, as the burrow has been closed and the female looks thin. However, some species such as C. collei tend to maintain their shape after laying and nests need to be carefully inspected. If the female aggressively defends the nest, she should be captured briefly until the eggs are collected and the nest can be excavated and refilled.

Finding eggs can be very difficult and care must be taken when digging, especially in corners where iguanas often deposit eggs. Eggs should never be rotated from the position in which they were found, and in order to keep track of individual eggs, numbers can be written directly on the eggshell with a pencil. Eggs should be carefully weighed and measured and placed in incubators.