Agression From Younger Gecko?

I have quarantined my new leopard gecko, Huayra, for a month and a half now (I realize that is on the short side for quarantine, I have done a fecal test with the vet, and it showed no parasites), I've also watched her before I got here as I bought her from a family friend who is a breeder, I introduced them on neutral territory, they went up, licked at each other, turned around and ignored each other, I did this for about a week, with the same results.
Now, I just put Huayra in my original geckos tank, and she started getting aggressive, shaking her tail, and striking at her. I don't understand why all of a sudden she got so aggressive, especially on another geckos territory. I assumed if either geckos were to get aggressive, it would be the older, and larger gecko because of an intruder on her territory. I know some geckos are just aggressive to each other their whole life, but why the sudden urge to attack?

Neutral territory means they're out of their living space. Sometimes they are too busy being curious and wanting to roam free to get aggressive with another gecko. Now once you put them inside a confined living space, they'll care more about every inch of the living space. They may react differently then.

Fast tail shaking & striking means the gecko is in the hunting mode, she could be hungry and started seeing the other gecko as food. I've seen younger geckos being dumb and doing that, then growing out of it. But I have also one that never grew out of it, 1 year+ old now she still strikes at whatever other gecko I put in the tank.

So if you have a gecko that behave that way, there's a good chance you won't be able to house her with another.

Mardy wrote:Neutral territory means they're out of their living space. Sometimes they are too busy being curious and wanting to roam free to get aggressive with another gecko. Now once you put them inside a confined living space, they'll care more about every inch of the living space. They may react differently then.

Fast tail shaking & striking means the gecko is in the hunting mode, she could be hungry and started seeing the other gecko as food. I've seen younger geckos being dumb and doing that, then growing out of it. But I have also one that never grew out of it, 1 year+ old now she still strikes at whatever other gecko I put in the tank.

So if you have a gecko that behave that way, there's a good chance you won't be able to house her with another.

Thanks Mardy, I'll try once more after she has been fed, and if she does it again, then I'll just keep them separated for good. So you're saying she thinks my other leo is food, so she's just not trying to fight?

She could be trying to fight. Smaller doesn't mean much when it comes to attiude. The smaller lion will attack the resident male lion in anticipation of his expected attack. He who attacks first usually gets the upper hand. It could be a way of saying " hey look I might be small but I'm tough, don't mess with me", or it could be intimidated so itstaking the preemptive strike so to speak... could be a multitude of reasons... bottom line is shs not comfrtable being confined in a tank with another leo so cohabitating might be something you want to avoid.