Long-term observations of fairy rings on Shillingstone Hill in Dorset, England, further suggested that the cycle depended on the continuous presence of rabbits. Chalky soils on higher elevations in the counties of Wiltshire and Dorset in southern England used to support many meadow-type fairy rings. Rabbits crop grass very short in open areas and produce nitrogen-rich droppings. Mushrooms need more soil nitrogen than grass does. A ring can start from only a few spores from which the mycelium develops; the fruiting bodies of the mushrooms only appearing later, when sufficient mycelial mass has been generated to support them. Subsequent generations of fungi grow only outwards, because the parent generations have depleted their local nitrogen levels. Meanwhile, rabbits keep cropping the grass, but do not eat the fungi, allowing them to grow through their competition to tower, relatively, above the grass. By the time a circle of mushrooms reaches about in diameter, rabbit droppings have replenished the nitrogen levels near the centre of the circle, and a secondary ring may start to grow inside the first.