measured hundreds of thousands of individual sand grains from across the dunes; and used satellites to see temperature and moisture changes throughout the year. Toward the western side of the dunefield, the dunes are more than tall, and they become progressively smaller toward the eastern edge, until they come to an abrupt stop at the eastern boundary. Throughout the dunes, water is only a few feet (a meter) from the surface and very salty, but toward the western edge of the dunefield, the water is older and even saltier. The depth to groundwater also decreases from below the surface on the eastern end to only on the western end of the dunefield. The dunes at the western end have very little vegetation and move very quickly, while the dunes on the eastern end move very slowly and are very vegetated. Toward the western edge, the sand grains become larger and have all different shapes, while at the eastern edge they are all very small and round. The dunefield is much cooler and wetter than the surrounding hot, dry desert soils based on satellites images. Scientists have discovered what appear to be old lakeshores beneath the dunes using laser scanning technology. At each of these old lakeshore terraces, the dune movement and type of dunes changes greatly. Ecology More than 600 invertebrates, 300 plants, 250 birds, 50 mammals, 30 reptiles, seven amphibians, and one fish species inhabit White Sands National Park. Animal species that have a white, or off-white, coloration include three mammals, three reptiles, one amphibian, and numerous insects. At least 45 species are endemic, living only in this park, with 40 of them being moth species, along with the Apache pocket mouse (Perognathus flavescens Apachii), White Sands woodrat (Neotoma micropus leucophaea), bleached earless lizard (Holbrookia maculata ruthveni), and two camel crickets. Flora The plants at White Sands National Park stabilize the leading edges of the dunes, providing both food and shelter for wildlife. Humans have made extensive use of the dunefield's native plant life, using some for food and others to create cloth and medicine. Native Americans wove mats with the thicker blades of grass, and consumed some of the grass seeds. The park's flora must be tough to live in the nutrient-poor alkaline soil of the dunefield. Drought-tolerant plants are able to survive in temperatures that range from sub-freezing to over , depending on the season. Many of