Blue Iguana Recovery Program

Eggs and Hatchings

The Nesting Female

A nesting female devotes a lot of time and energy to finding the right spot for her nest chamber. As she digs, she blocks the tunnel behind her with loose soil. She tunnels until she finds exactly the right depth, temperature and humidity for the incubation of her eggs. Once satisfied, she digs out an underground nest chamber, and works the soil into a fine base usually about a foot below the surface. In total darkness she lays anywhere from one, to twenty or more eggs: the older, larger females are able to produce the most.

Laying and Hatching

Emaciated and exhausted, she digs her way back out through the blocked access tunnel, packing the soil behind her to seal in the nest chamber. Once back outside she packs more soil into the tunnel entrance, and rams it with her snout, all four legs pushing, to compact the earth as if it had never been dug. Then she scatters leaves all over the area, until the nest is completely disguised. Only when the nest is secure does she allow herself to feed again. As she frantically fills her starved body she remains close to the nest, making sure no other iguana tries to dig in the same area.

Meanwhile underground, the eggs are taking up moisture from the earth, and gradually filling out until they are tight and under slight pressure. The embryos develop at the mercy of the elements, taking 65 to 100 days or more to hatch depending on temperature. The eggs are vulnerable to flooding or unseasonable drought, but if they escape those, a high proportion usually hatches successfully.

The hatching iguanas have a microscopic “egg tooth” on the tip of their jaw, which they use to slash open the leathery egg shell. In a drawn-out process often taking more than12 hours, the first hatchlings uncurl themselves out of the eggs, and lie exhausted by the effort, waiting for the others to emerge. Each hatchling has the remains of their egg yolk inside their abdomen, and can live off it for weeks before needing to feed or drink.

Once all the eggs have hatched and the hatchlings have regained their strength, they start to dig their way out of the nest chamber. The old tunnel is now no easier to dig than the surrounding soil, so they usually stab straight for the surface. They dig out through a single exit tunnel, one behind another, pushing the excavated soil down from hatchling to hatchling while the whole group move upwards. As soon as they break out to the surface, they scatter for cover. From then on, each one is on its own, in a very dangerous world!