(Syncerus caffer) inhabit the national park's central sector. Okapi (Okapia johnstoni), blue duiker (Philantomba monticola), bay duiker (Cephalophus dorsalis), Weyns's duiker (C. weynsi), yellow-backed duiker (C. silvicultor), water chevrotain (Hyemoschus aquaticus), red river hog (Potamochoerus porcus), aardvark (Orycteropus afer) and bongo (Tragelaphus eurycerus) were recorded in the northern sector in 2008. Harnessed bushbuck (T. scriptus) and giant forest hog (Hylochoerus meinertzhageni) are present in the southern sector. All of the topi (Damaliscus lunatus jimela) cluster to the south of Lake Edward in the Ishasha Flats region, and regularly cross the border into Uganda. Other ungulates present include Ugandan kob (Kobus kob thomasi), waterbuck (K. ellipsiprymnus), and common warthog (Phacochoerus africanus). Virunga National Park together with the adjacent Queen Elizabeth National Park forms a "Lion Conservation Unit". The area is considered a potential lion (Panthera leo) stronghold, if poaching is curbed and prey species recover. In the national park's northern sector, African leopard (P. pardus pardus), marsh mongoose (Atilax paludinosus), giant pangolin (Smutsia gigantea), tree pangolin (Phataginus tricuspis), crested porcupine (Hystrix cristata), Lord Derby's scaly-tailed squirrel (Anomalurus derbianus), Boehm's bush squirrel (Paraxerus boehmi), western tree hyrax (Dendrohyrax dorsalis), Emin's pouched rat (Cricetomys emini) and checkered elephant shrew (Rhynchocyon cirnei) were recorded during surveys in 2008. Reptiles The Semliki River provides habitat for Nile crocodile (Crocodylus niloticus). Several were observed at the northern shore of Lake Edwards in 1988 for the first time. Birds Of the Albertine Rift's endemic birds, Rwenzori turaco, Rwenzori batis, Archer's ground robin, red-throated alethe, Kivu ground thrush, collared apalis, mountain masked apalis, dusky crimson-wing, Shelley's crimsonwing, red-faced woodland warbler, stripe-breasted tit, blue-headed sunbird, regal sunbird, Rwenzori double-collared sunbird, handsome spurfowl and strange weaver were recorded in Virunga National Park's southern sector during surveys in 2004. Non-endemic birds recorded include Wahlberg's eagle, African goshawk, African hobby, harrier hawk, common buzzard, mountain buzzard, hadeda ibis, grey-crowned crane, black-and-white-casqued hornbill, black-billed turaco, African olive pigeon, tambourine dove, blue-spotted wood dove, red-eyed dove, brown-necked parrot, red-chested cuckoo, olive long-tailed cuckoo, barred long-tailed cuckoo, Klaas's cuckoo, Diederik cuckoo, blue-headed coucal, Narina trogon, white-headed wood hoopoe, white-necked raven, white-tailed crested flycatcher, African paradise flycatcher, white-eyed slaty flycatcher, African dusky flycatcher, white-tailed blue flycatcher, mountain oriole, speckled mousebird, cinnamon-chested bee-eater, grey-throated barbet, yellow-billed barbet, western tinkerbird, yellow-rumped tinkerbird, cardinal woodpecker, olive woodpecker, black saw-wing, Angola swallow, Alpine swift, mountain greenbul, yellow-whiskered greenbul, common bulbul, white-starred robin, Archer's ground robin, white-browed robin-chat, African stonechat, rufous