Normal fluids "consumption"

In the last week, I have found the fluid level in the 4 wheel drive transfer case a little low and the dealer found the level in the rear differential low (took about 1/2 pint to top). Funny that at the last oil change the rear differential was fine. I don't know if they checked the 4 WD transfer case. Almost seems like at the last service, someone opened the bottom drain plug instead of the top check/fill hole. Anyone have any comments or experiences here????