1. Mammals
Over sixty mammal species have been recorded in Semuliki Valley, representing a mix of forest-adapted and savannah-edge fauna. Key species include:
- Forest elephants (Loxodonta cyclotis), which use the valley for migratory corridors connecting to the Congo.
- African buffaloes (Syncerus caffer) concentrated near swamp fringes and riverine meadows.
- Waterbucks, warthogs, and bushbucks are common along open glades and seasonal flood zones.
- Leopards (Panthera pardus) occur in low density, with camera trap records near the Kirumia sector.
- Pygmy hippopotamuses (Choeropsis liberiensis) have been occasionally reported along secluded tributaries, though no confirmed population assessment exists.
Large mammal distribution is influenced by water availability and vegetation density. Most species remain active during early morning and late evening, adapting to high humidity and heat.
2. Primates
Semuliki Valley supports one of Uganda’s most varied primate assemblages, alongside those of Kibale and Budongo. Documented species include:
- Olive baboon (Papio anubis)
- Red-tailed monkey (Cercopithecus ascanius)
- Black-and-white colobus (Colobus guereza)
- De Brazza’s monkey (Cercopithecus neglectus), typical of central African forests
- Chimpanzees (Pan troglodytes schweinfurthii), primarily restricted to Toro–Semuliki Wildlife Reserve
Behavioral research indicates that chimpanzee groups here exhibit hybrid foraging patterns, alternating between woodland fruiting trees and riverbank galleries. This adaptation aligns with their seasonal habitat shifts between forest blocks and open woodland.
3. Avifauna
The valley’s birdlife is internationally recognised. Over 440 bird species have been recorded, making it one of Uganda’s most significant ornithological destinations. It includes several Congo–Guinean biome endemics rarely observed elsewhere in East Africa.
Notable species include:
- Lyre-tailed honeyguide (Melichneutes robustus)
- Long-tailed hawk (Urotriorchis macrourus)
- Nkulengu rail (Himantornis haematopus)
- Crested malimbe (Malimbus malimbicus)
- Shoebill (Balaeniceps rex), found along papyrus fringes near Lake Albert
- Black dwarf hornbill (Horizocerus hartlaubi)
The Kirumia Trail and Sempaya–Ntandi sector offer prime viewing zones for most forest endemics. Birding records peak between June and August, aligning with drier conditions and fruiting cycles.
4. Herpetofauna and Invertebrates
Semuliki supports a remarkable range of reptiles and amphibians, including species with Congo–Basin affinities absent from other Ugandan reserves. Noteworthy examples include:
- Forest cobra (Naja melanoleuca)
- Three-horned chameleon (Trioceros johnstoni)
- African rock python (Python sebae)
- Swamp night frog (Hyperolius cinnamomeoventris)
Invertebrate diversity remains under-studied, though surveys have identified more than 300 butterfly species and several rare moths of the Saturniidae and Nymphalidae families.
Aquatic macroinvertebrates play vital roles in nutrient cycling within the Semuliki River basin.