in my opinion the Argentine Tegus make the best pets. they are normally very calm and can be handled and let loose to run around without many concerns. But they are the biggest by far. As far as male or female it depends on you and what you want. Females are going to get smaller and are going to be a little more drab as far as color goes. They can SOMEtimes get a little aggressive towards breeding season. i always went with males because i thought they looked more impressive with their heads. The others arent going to be as good of a pet. Blue tegus are pretty good though and bit smaller than the Argentines. Can be more expensive and a little harder to find good ones. Colombians are not the best for pets if you are looking for something you can get out. They are strictly carnivores (some MIGHT eat a little fruit). These are normally pretty aggressive but some can be calmed and are smaller than the others. The chilean dwarf tegu is small around 18-26inches in length. Can be very skittish, but normally not aggressive.
I like the Argentines the best. The reds are going to need more fruit and humidity than the Black and Whites though.
ALL tegus are going to eat a LOAD of food. These guys can take down food like they've never eaten before and they do that everyday.
Cages are going to need to be large. a 6x3x3 cage is minimum for the larger ones and the Chileans can go in a 4x2x2. They LOVE to dig and will need a LOT of dirt to dig in.
Feel free to ask anymore questions. Best of luck
later
