In years past, Columbian Tegus (
Tupinambis teguixin) were all imported wild caught specimen and they were very aggressive. More recently there are a lot of people breeding them in captivity and these are not nearly as aggressive. Though do be cautious because there are still a lot being imported.
　
But... while captive bred Columbians are much better than their wild caught counterparts... they are not nearly as friendly or easy to tame as Argentinean Tegus...
　
　
"Argentinean Tegu" is a somewhat generic term used to describe Black & White Tegus (
Tupinambis merianae), Red Tegus (
Tupinambis rufescens) and Blue Tegus (an odd color form of
Tupinambis merianae).
　
Black and Whites are the most common and are the baseline for Argentinean Tegus. Males generally reach 4 and females generally reach 3. They are very easy to tame and can make great pets, but naturally any animal kept in a small (or otherwise inadequate) enclosure will naturally be stressed. Stressed animals are never friendly animals
　
Red Tegus are rumored to (on average) get a teeny bit bigger and have a teeny bit more potential for aggression. Though neither of these rumors are significant enough to make any quanitative difference. So essentially the difference between Reds and B&Ws is color.
　
Blue Tegus have not been classified as their own species and are technically considered a locale of
Tupinambis merianae. I personally would not use the term morph to describe them as the term morph is generally reserved for a genetic mutation that passes down systematically (recessive, dominant, co-dominant, incomplete dominant, etc). This is not the case with Blue Tegus.
　
I think its also relevant to mention that Blue Tegus entered the Pet trade from a single small group (most likely siblings). This small group was then bred together, then their offspring bred together, etc. The smaller size and (sometimes noted) other health concerns are commonly attributed to excessive inbreeding. Since the Blue trait is not recessive, dom, co-dom, etc any out crossing with other types of Tegus simply waters down the Blue. Once watered down the Blue cannot be cleaned up making out crossing true Blue Tegus impossible.
　
　
My advice would be to raise your own Tegu from hatchling. The vast majority of adult Tegus for sale are being rehomed because they are problemed animals or because they have outgrown their enclosure and have thus been living in cramped quarters for quite some time. Again, too small of an enclosure results in a stressed animal, and stressed animals are not friendly animals.
　
　
Argentinean Tegus do seek out and enjoy human interaction. So they do not make good display animals, at least not in an indoor enclosure. Mine spends 2+ hours 5+ days a week wondering freely around the house and often seeks out direct human interaction while doing so. As a matter of fact he has interrupted me several times while writing this. While many of you reading this will assume he simply seeks contact due to body heat, those of us who own Arg Tegus generally have numerous stories that discredit such concepts (Ill spare you the story telling this time).
　
But I digress, my point was (supposed to be) do not get a Tegu unless you plan to spend ample time interacting with him. But if you can supply a large enough enclosure and interaction time
if a puppy like reptile is what you are looking for
Oh My God get an Arg Tegu!
　
　
An Arg Tegu would love your modified outdoor dog run. Mine lives on a 6 x 12 deck/balcony in the summer months (Charlotte NC). I look forward to buying a house (again) to build him a proper outdoor enclosure.
　
Its hard to say what winter home he will need. Many Arg Tegus can simply hibernate through the winter and are quite inactive in late fall and early spring. But not all will do so. Mine has wintered differently every year and this winter he has barely slowed down at all.
　
I have an 8 x 3 enclosure mine spends the winter in and in all honesty its probably not big enough (for ideal standards). The fact he gets so much free roam time keeps things peaceful, but it is not a wise idea for me to rely on this as there is no guarantee life will continue to give me this much Tegu time in the cooler months.
　
　
I bought my Tegu from Bobby Hill / Varnyard who hosts a Tegu forum at
www.tegutalk.com . I highly recommend doing plenty of research before buying any Tegu and I believe Tegu Talk is a great place to start (but do not limit yourself to just there). The following link is to a picture thread I posted here at MFK a couple of days ago.
http://www.monsterfishkeepers.com/forums/showthread.php?t=398405
