Incubation and hatching
When setting up the incubator, it is best to use a mixture of one part of perlite to one part vermiculite.
This is what I have found to work the best. I use four parts of this mixture to one part water. Note, if this mixture becomes too wet, mold will start to attach to the eggs. This is not good for tegu eggs. I have found that the eggs do much better if they are a little dry, then too moist. Tegu eggs are not like most reptile eggs. They do not get softer the longer they incubate. The eggs get larger and firmer the farther they incubate. This mold can cause a breach in the eggs. Tegu eggs have pressure inside them. Most reptiles produce firm eggs when they are laid, tegu eggs are dented and soft. They start becoming firm within a few days of incubation. Most reptiles eggs become dented when they get close to pipping. When tegus pip, fluid squirts up to twelve inches from the egg. I have not seen this in other reptiles.
The temperatures for incubation are best between 86° F to 90° F. I have heard of cooler temperatures as well as warmer, but this has worked best for me. The incubation period, I have found to be between 58 and 60 days. This time can run a few days longer or shorter. It is also not good to pip tegu eggs. These eggs will hatch if a healthy baby is inside. Tegu babies will not stay in the egg like most reptiles, they will bust out as soon as they pip.
I have heard of incubation times of 40 days to 120 days, but this is the time I have recorded with four different clutches. It would also depend on the temperature, a hotter temperature would tend to cause them to hatch faster, but the babies would be less healthy. Also at a cooler temperature the eggs would hatch slower. However I think 120 days is way off on time. I read this in a book, but I found this information hard to believe.
Babies need to be removed as soon as they hatch. They need to be offered some food as soon as they hatch. Hatchlings will sometimes start to feed within hours of hatching. Others will feed the following day. I offer medium crickets to fresh hatchlings, they seem to take these best. You will also need to have two different tanks set up for the hatchlings, some hatchlings might be smaller and less active. These will need to be removed and put into seperate enclosure then the larger more active babies. I use a 20 gallon long tank for hatchlings. This is a great starter tank. I put a heat lamp with a 65 watt bulb at one end. I also use a UVB, UVA strip light on top. This way the hatchlings can get warm or cool off as needed. A shallow water dish, and newspaper for the sub straight. The baby hatchlings will keep their bellies cleaner on this. This way no infections will start while the bellies seal. Remember Argentine tegus can take cooler tempretures than most other lizards. The basking side of the enclosure needs to be between 95*F and 110*F. They also need a cool side to the enclosure as well, this needs to be no warmer than the lower 80s*F.