Try reporting that in context. That was the only species where it failed. May I add, they were wild caught young animals, not captive hatched. Also they were not hatchlings, but instead, young animals. Which does lower the chance of success.
Also, behavior is not clear cut, or math. If you do this, it will not always result in that. Such is behavior. Its about percentages. If you raise them together, a high percentage of the time it will work. This is true with all species.
Some individuals will simply not get along, and I don't care what species or what kind of animal, social or not. Its about indviduals.
In that group, the male tricolored, did not get along with any monitors. He did not pester others, or harass them, he simply walked over, and killed them with one bite over the heart, a kill shot so to speak.
It taught me lots, it taught me that if a monitor wants another one dead, they know how to do that.
Anyway, what you and others need to understand, working with varanids is all about BEHAVIOR(ethlogy) and not math. Behavior is fluid and not set in stone. Varanids are very generalized physically(for lizards) But very specialized behaviorally.
The one single tool, trick, husbandry tool, of raising them together is good, but its only one tool of many. You should really ask what raising them in groups does for the monitors. Because that is the key. Cheers
