From what I've read Tegu's do have a moderate feeding response, and they can learn their feeding times. My suggestion is to either put him in a box to feed him (which can fit in the cage, and he can crawl out on his own) or to have a means of getting the food into the cage without him knowing.
If you feed him crickets, you can very carefully remove their jumping legs and put them in a dish for him to eat out of. Mealworms cannot escape either.
My suggestion is to feed him out of a bowl, but not let him see your hand, so he doesn't associate your hand with food so when hes much bigger, you dont recieve nasty bites!
Also, if you build a cage, my friend told me that you can have one end of the cage devoted to feeding. Such as having a board seperating it, and you can remove it from the outside (like a castle gate or something lol). It doesn't need to be a large space, just big enough for the bowl. Its kinda hard to explain, but the concept is that he never sees your hand go into the cage, rather just the door open to his food area.
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Currently have: Antherystic Corn Snake, Amelanistic Corn Snake, Oakatee Corn Snake, Leucistic Texas Ratsnake, and an Eastern Fox Snake
Have had:
Ghost Corn Snake, 2 Japanese Firebelly Newts, 3 Green Treefrogs, Cuban treefrog, Eastern Box Turtle, 3 Leopard Geckos
Saving for:
Red Tail Boa, Jungle Carpet Python, Large Lizard