from similar mammals elsewhere, probably due to isolation of the Imatong forests from other forests by wide areas of semi-arid savanna. This isolation dates back to the last Pleistocene Pluvial period about 12,000 years ago. The forest contains many birds found in no other part of South Sudan, and is a resting place for European songbirds en route to their overwintering places in East Africa. Birdlife includes the endangered spotted ground-thrush Zoothera guttata. People The villages and settlements of the region are inhabited by Nilotic people including Lotuko in the east, Acholi in the west and Lango in the southern part. They practice subsistence farming and raise some livestock. The people of the area mostly live on the plains at the foot of the mountains, but recently they have been forced to move into the mountains as high as to find land for farming. Their agricultural practices have led to serious erosion of the steep slopes. Relatively small numbers of the people practice Christianity. Foreign Christian missionaries have been entering the remote mountainous areas since 2005. European explorations Little is known of the area before the arrival of Europeans. The explorer Samuel Baker was the first European to visit the region, travelling in the northwest and west of the area in 1863. He visited Tarrangolle (Tirangole), and observed then unnamed mountains to the south. Later he passed through them, the present-day western Acholi sub-range of the Imatongs. Emin Pasha made a trip in 1881 in which he traveled along the eastern foothills of the mountains and then southwest to the White Nile. J.R.L. Macdonald passed through the region in 1898 on a patrol towards Lado, and later the Ugandan colonial government established a post at Ikotos, just east of the mountain range. After 1929 the British established an observation post on the north side of the range, above the village of Gilo (1800 m) at an altitude of about . Maps The official map of the Anglo-Egyptian Sudan published in 1922 only showed the outlines of the mountains. The first map to show the mountain range and give it the name Imatong Mountains was published in the Geographical Journal in May 1929. It was prepared from a compilation of the Anglo-Egyptian Sudan Government Survey Department. The first detailed map of the mountain range appeared in 1931. Botanists and biologists Apart from a field visit by R. Good to Gebel Marra,