Some things for Roger to think about. First how far they "can" range in the wild is sorta like saying you can swim like that Phelps fellow or the Thorpedo(retired). That is the exception. In fact, monitors do not range very far at all, unless they are forced to by not finding what they are looking for. If they cannot find what they need, they roam.
To understand the above is very very important in understand monitors(all reptiles) in nature and in captivity.
Wild and captive monitors if supported grow up and seek to fullfil their design. When wild monitors find a suitable area that supports them, they STAY there. Roaming is for reason, its to find a place(tools) to support them. If they find it, they do not roam. Its kinda very very simple. Unfortunately, those science guys do not understand what monitors DO in the first place, so they cannot understand when or why they roam to find it. They list a range they will or have used, but they do not offer context to explain why they use it. In many cases the larger distances are because they have radios installed in the monitors and they are running from humans with antennaes growing out of their heads.(other predators can cause the same reaction, sans the radio)
In other words, the individuals that stay put, do so because they are successful, the individuals that roam, do so because they are not successful. The successful ones are seeking to stay successful. The unsuccessful individuals are seeking to become successful. Simple if you think about it.
Its important that you understand this. They do not dig excessively unless the reason they dig is not met. They dig to make a suitable burrow(home/shelter) If allowed to make a suitable shelter, they slow down the digging almost to a stop.
If they want to feed all the time, that means they are not fed enough, it really is that simple. Of course the husbandry conditions must support the use of that much energy.
If they bask all the time, that means the reason they bask is not being met either. Are you getting this?
I once told a story of my female Lacie, a sweet thing she was. She loved her cage and me. She never tried to get out. I could leave the door open(did many times) and she would not leave. Except for when she was about to lay eggs. She would sit and look into the cages next to hers. She would dig at the side trying to get over. So what am I to do? I cut a hole in the cage and added a door and of course she went right over and laid her eggs and came back. Don't ask me, her cage had the same(to my eyes) stuff the other cage had, in her cage.
I said she liked me because everytime I went into the cage she would come over and lay her head on my lap(attending) I think she bonded to me as she was the first female I hatched and I could not keep my hands off her.
The point I am trying to make is, while a healthy adult nile is indeed a large lizard and even your room is too small. The actual size of the cage can be minimized by including the actual needs of the individual.
In your case, a kidding pool of dirt is more about kidding yourself then supporting the needs of the nile. Thats very common here on this site. You put in a kidding pool of dirt, ONLY so you can say you did what you were told they needed. Thats dirt and you put it in there. But does that dirt allow what the monitors are tying to accomplish?
There are a few books with diagrams of burrows. They show a tunnel then a den. Oh like any old animal burrow. I think one shows a pop up or escape burrow, incase something comes in the main entrance(a snake) The reality is, those are simple burrows. You know like a house a first grader would build, compared to an adult. There are indeed dozens of different kinds of burrows.
Of course the base is the simple tunnel with a den. Then of course there are tunnels with several dens, then networks of tunnels connecting all sorts of different rooms. There are burrows they use for long periods(complicated) and simple overnight burrows like those drawn, in those books, a short tunnel ending in a sleeping area.
The problem is, your monitors are not making overnight burrows, as they live there, they are attempting to make living burrows, you know the complicated ones. They will keep digging until they make the most minimal of living shelters.
I say this in hopes you understand, they do not dig to dig, they dig to accomplish a goal. They do not hunt to hunt, they hunt to catch something. They do not bask to bask, they bask to reach a certain temp. I say this to help you understand, if they accomplish their goals, then they are no need for roaming.(extenting the area needed to support a goal/task)
Please consider, this also means having a mate. They will roam to find and attend a mate. Once they do so, they will stay in the area of that mate for as long as they can. Their whole life is allowed.
Provide all these things and you can keep the cage size to a minimum. This is key to understanding wild and captive monitors. Cheers
