My gecko Toby moves his tail back and forth whenever he is about to attack his food, but he also does it when I put a finger in front of him. Is that sort of tail movement just pre-attack behavior? I'm just not sure what it means exactly.

leopards do that when they are hunting but they will also do it when they feel threatened or they are just ****ed off or annoyed. males will do it to each other before they fight.

Its totally normal.

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MARSHA

:D I'm smiling because I have no idea whats going on!

i am actually personally familiar with these leopard geckos
so I will expand a little on the question:

we introduced toby to his "little sister" charlotte, a high yellow(i say girlfriend next year but bitty thinks thats weird lol) and toby ignored her for a bit, but then locked on, realized "too close for missles, switching to guns"... hunched down football style, and lifted his tail straight up and started to slowly sway it. I interpreted this as an immenant attack so I put my hand in the cage which made toby settle down some. this is what prompted the question. toby has done the same thing since we got him with my finger next to the glass. we just wondered what it was.

he used to run after this which made me think the wagging was a lure to a predator- ie. make the predator take the detatchable tail - TORO! TORO!

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0.0.1 - Jack, Ghost corn, never sexed, but its a He darnit
1.0.0 - Neo, Columbian Redtail Boa. Everybody's best buddy :) except my roommate.... he bites my roommate....

if hes doing that to your female gecko hes not neccisarly threating her but hes seeing weather or not is another male gecko. its 100% natural all male geckoswill do it when meet a new gecko, if its a female the female won't respond so the male will stop but if its another male he'll do the tail wag back and there will be a fight. so they should both be fine just keep an eye on them because a fight could still happen. and when you put your finger to the glass and he does it he just thinks your finger is dinner lol