Home | Field studies and notes | Notes from the Field – An Aggressive Black Tegu Tupinambis teguixin (merianae)

Notes from the Field – An Aggressive Black Tegu Tupinambis teguixin (merianae)

While workBlack Teguing with Green Anacondas in the central Venezuela llanos (please see my article Hunting Anacondas in the Venezuelan Llanos) in the late 1990’s, I was delighted to find that Black Tegus, one of my favorite lizards, were quite common in the area.  Sometimes referred to as “New World monitor lizards”, it was indeed hard not to make that comparison when watching tegus hunting.  Active and intelligent, these stout lizards ate just about everything they came across – other lizards, snakes, turtle and bird eggs, small mammals, fish, frogs, crabs, large insects and carrion – and were major predators in this flooded grassland habitat.  I managed to catch a few young tegus, but old, battle-scarred individuals were impossible to approach, fleeing with amazing speed at the slightest move in their direction.

One morning I was scanning an area where I had seen a pair of Giant Anteaters a day earlier, hoping for another look, when my binoculars picked up a co-worker doing what appeared to be an odd dance of sorts.  Upon closed inspection, I saw that he was repeatedly jumping back from a yard-long black animal that was hurling itself at his leg.

I ran over and found him in a pitched battle with a large male Black Tegu.  The animal was not cornered and had ample opportunity to turn and run, as they invariably do, but simply refused.  Nest-guarding has been reported in some populations, but among females only and there was no nest to be found here.  Upon subduing the ornery fellow I found that he was uninjured, and capable of moving normally.

The only explanation that seemed to make any sense (outside of a bad temper!) was that he had not warmed sufficiently for a fast burst of speed (it was morning, and the lizard was in grass flooded by cool water).  However, he seemed to be exerting as much energy fighting as he would have by running!  Upon being released, he continued to hold his ground until we relinquished what was obviously a prized piece of real estate.

Of course, there are general rules as to typical species’ behaviors, but reptiles and amphibians show quite a variance in “personality traits” – this may assist them in adapting to changing environmental conditions and to captivity.  .

An interesting article on Black Tegus and related species is posted at:

About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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