What is the tank set up like? Did the frog have access to clean water, and if not, how long has it been without it? How moist is the tank? Are there any heat lamps or pads on or under it? Also could you try to describe the frog a bit more? I know it may be hard if you've never been a frog person, but how large is it and does it have any other characteristics that stand out to you? Is there any possible way that you can get a picture of it?
Without knowing what type of frog it is and what the current setup is like, it's a little tough to tell you exactly what to do, but if the tank doesn't have a water bowl, try adding a shallow one with a little dechlorinated water in it no higher than the frogs legs. We don't want him to drown. You said he sits in his "box" all day long? That's odd for a tree frog...please try to help us identify the frog so we can help you more. Also...how do you feel about picking it up? Another option if you really want to get involved would be to place the frog in a separate container, such as a plastic "Kritter Keeper" or some other comparable container with an unbleached, plain white paper towel bottom. Dampen the towels a bit with declorinated water, and still provide shallow bowl or dish of water that it can easily climb in and out of. Also put in a a few fake leaves or something else suitable that the frog can hide under if it feels the need. Get this all set up before you try to move the frog, that way you can move it and leave it alone to get accustomed to its new surroundings. When you return later you can try to feed it crickets no larger than the frogs head, but only put in one or two to see if he is indeed interested in eating. If he does eat, that is a great sign and he may not need much care. The benefits of keeping it this plastic enclosure is that you can monitor how much he eats and eliminates. I hope this helps, but still try to ID the frog as some of this may change according to what species it is. Keep us posted, and if you want, shoot me an email if you have anymore questions. Good luck!
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*~~Whitney~~*
There are two types of people in this world, good and bad. The good sleep better, but the bad seem to enjoy the waking hours much more.