53 Migration of ungulates is under pressure worldwide from range contraction, habitat 54 loss and degradation, anthropogenic barriers and poaching. Here, we synthesize and 55 compare the extent of historical migrations of the white-bearded wildebeest 56 (Connochaetes taurinus) to their contemporary status, in five premier East African 57 ecosystems, namely the Serengeti-Mara, Masai Mara, Athi-Kaputiei, Amboseli and 58 Tarangire-Manyara. The current status, threats to migration, migratory ranges and 59 routes for wildebeest were characterized using colonial-era maps, literature reviews, 60 GIS and aerial survey databases, GPS collared animals and interviews with long-term 61 researchers. Interference with wildebeest migratory routes and dispersal ranges has 62 stopped or severely threatens continuation of the historical migration patterns in all 63 but the Serengeti-Mara ecosystem where the threat level is relatively lower. 64 Wildebeest migration has collapsed in Athi-Kaputiei ecosystem and is facing 65 enormous pressures from land subdivision, settlements and fences in Amboseli and 66 Mara ecosystems and from cultivation in Tarangire-Manyara ecosystem. Land use 67 change, primarily expansion in agriculture, roads, settlements and fencing, 68 increasingly restrict migratory wildebeest from accessing traditional grazing resources 69 in unprotected lands. Privatization of land tenure in group ranches in Kenya and 70 settlement policy (villagization) in Tanzania have accelerated land subdivision, 71 fencing and growth in permanent settlements, leading to loss of key wildebeest 72 habitats including their migratory routes and wet season calving and feeding grounds. 4 73 These processes, coupled with increasing human population pressures and climatic 74 variability, are exerting tremendous pressures on wildebeest migrations. Urgent 75 conservation interventions are necessary to conserve and protect the critical 76 wildebeest habitats and migration routes in East Africa. 77 78 Introduction 85 Large mammal migrations are among the most-awe inspiring of all migrations [1]. 86 These migrations, the seasonal and round-trip movement of large herbivores between 87 discrete areas, are under increasing pressures worldwide. Globally, migrations of 6 88 out of 24 species of ungulates are either already extinct or their status is unknown [2]. 89 Of the remaining ungulate mass migrations, most occur in six locations in Africa, 90 including the white-bearded wildebeest (Connochaetes taurinus Burchell, 1823) 91 migration in the Serengeti-Mara ecosystem of Kenya and Tanzania [2]. Range 92 restriction and alteration, degradation and loss of habitat due to agriculture, poaching 93 and barriers that block migration, such as fences, roads, railroads, pipelines and 94 settlements have progressively disrupted historical migratory routes and decimated or 95 driven rapid population declines of many of the once spectacular migratory herds over 96 the 20 th century [1,3-5] . 5 97 98 Because migration enables populations to grow to large abunda...