The Upper Nile Valley and Abyssinia were also significant sources of slaves in the Ottoman Empire. Although the Christian Abyssinians defeated the Ottoman invaders, they did not tackle enslavement of southern pagans as long as they were paid taxes by the slave traders. Pagans and muslims from southern Ethiopian areas such as kaffa and jimma were taken north to Ottoman Egypt and also to ports on the Red Sea for export to Arabia and the Persian Gulf. In 1838, it was estimated that 10,000 to 12,000 slaves were arriving in Egypt annually using this route. A significant number of these slaves were young women, and European travelers in the region recorded seeing large numbers of Ethiopian slaves in the Arab world at the time. The Swiss traveler Johann Louis Burckhardt estimated that 5,000 Ethiopian slaves passed through the port of Suakin alone every year, headed for Arabia, and added that most of them were young women who ended up being prostituted by their owners. The English traveler Charles M. Doughty later (in the 1880s) also recorded Ethiopian slaves in Arabia, and stated that they were brought to Arabia every year during the Hajj pilgrimage. In some cases, female Ethiopian slaves were preferred to male ones, with some Ethiopian slave cargoes recording female-to-male slave ratios of two to one.