I have mine in a 175 reptarium wrapped in plastic. They really like the height and climb quite a bit. It isn't about activity, it's about climbing. Besides, if you were to make like a rock and sit in a corner all day you would find out that they move around quite a bit. They don't just sit there all day long.
While I am feeding my babies I hear my lepidogaster, what I am guessing you have, moving around in their viv. They run down the vine to the food bowl and then jump to the water dish. They climb the ropes up the sides to the ferns and sit a while then back to the vine again where the climb to the top to find a suitable bunch of leaves to hide in.
This is repeated throughout the day sometimes to feed, sometimes to poo, sometimes to breed. They do tend to hide when you are there as this is the nature of things, hide from the beast that might be coming to eat me!
So, what I am saying is that in spite of the size, they do need at least 3' in height for climbing. If you cage a canary you could say that it is a tiny bird so it must not need a very large cage. However, in order for it to be healthy and happy it must have room to fly. Does it fly all of the time? No! But it does need to fly when it wants so it should have a large enough cage to fly when it wants. The same applies to the little MHD that you have. It will reward you with better health and vigor if you allow it the space that it needs.
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Marcia - FroggieB Dragons
www.froggieb.com/MHDHome.html