The currently accepted hypothesis is that the precise alignment allows the termites to keep their homes comfortable. Northern Australia gets extremely hot during the day and cool at night, and researchers believe termites have somehow harnessed the power of the earth’s magnetism to strategically climate-control their homes.
Graham Brown, a former curator of insects at the Northern Territory Museum explains that these towering mounds are essentially termite apartment buildings. A single nest may contain tens of thousands of termites. To comfortably house all those insects, the mound needs to have just the right architecture. He says all the little rooms, or galleries, need the proper moisture level and a good internal temperature, and the north-south alignment of the mounds seems to help keep the termites comfortable.
Source