What does the behavior mean? Should I be worried?

[Zacattack95]

I've seen this happen off and on for a while and I don't know what it means. I'm not sure if I should separate our two cherry heads. The older one, Tank, is about 2.5 years old and the younger, Squirt, is a little over a year.
Tank gets on top of Squirt while shaking and bobbing his head pretty fast. A newer development is Tank now makes sounds once in while during it. The sound is hard to describe. It's kinda like a medium to low pitch grunt. We don't know the gender of either of them.
Attached is a picure I captured of the behavior. I also have video, but I'm not sure how to attach videos on here.

 

[TheLastGreen]

Yup, seperate them immediately, the bigger one is showing dominance, @ZEROPILOT is a pro on redfoots

 

[ZEROPILOT]

Yup, seperate them immediately, the bigger one is showing dominance, @ZEROPILOT is a pro on redfoots

Classic bullying.
Tortoises are solitary. When in captivity they can not escape each other and it is very stressful.
If you have the space outside. You can often keep more than 3 females together. Or a single make per at least 3 females.
This usually spreads out the agression. But not always.
Some tortoises.....even Redfoot are just extra territorial.
This is something that all adult males do. But as you're seeing. It can also happen in sub adult males or females too. And on rare occasions adult females.
Two tortoises are a very bad idea. Even with a relatively calm species like REDFOOT.
Groups or single tortoises are best.
This will lead to illness and eventually death.
I know it's hard to comprehend.
Us mammals like company.
Tortoises do not

 

[wellington]

What the other two said ASAP.