Birdlife is especially spectacular in Semuliki with 441 recorded species, representing 40% of Uganda’s total bird species and 66% (216) of the country’s forest bird species. The list is expanded by the riverine habitat and a fringe of grassland in the east of the park. There are numerous rarities; 46 Guinea-Congo biome species are found nowhere else in East Africa while another 35 can be seen in only two or three other places in Uganda. Five species are endemic to the Albertine Rift ecosystem. Species to look out for here include the Nkulengu Rail, Yellow-throated Cuckoo, Piping Hornbill, Red-billed Dwarf Hornbill, Black Dwarf Hornbill, White-crested Hornbill, Black-casqued Wattled Horbill, Red-rumped Tinkerbird, African Piculet, White-throated Blue Swallow, Yellow-throated Nicator, Leaf-love, Swamp Palm Bulbul, Lemon-bellied Crombec, Maxwell’s Black Weaver, Crested Malimbe, Red-bellied Malimbe, Blue-billed malimbe, Chestnut-breasted Negrofinch, Orange-cheeked Waxbill.
The forest is home to 53 mammals of which 27 are large mammals. 11 species are endemic to the park including the pygmy antelope and two flying squirrel species. It is also home to the peculiar water chevrotain, known as the “fanged deer”.
The park is home to forest elephant and buffalo which are smaller versions of their savannah-dwelling relatives. The forest is remarkably rich in primates including the chimpanzee, baboon,grey-cheeked mangabey, black-and-white colobus, Central African red colobus, blue, red-tailed, de Brazza’s, vervet, and Dent’s mona monkeys. Nocturnal primates include the potto and bushbaby. Hippos and crocodiles are common along the Semliki River.