The gorilla trek ends in the afternoon. The vehicle returns to the lodge. Drinks are served on the veranda. And then, at a certain point in the evening, something extraordinary happens: the forest becomes audible in a completely different register. The daytime sounds — birdsong, primate calls, the distant crack of a falling branch — are replaced by the night forest’s own vocabulary, and for visitors who are awake to hear it, the sonic landscape of Bwindi after dark is as remarkable as anything encountered during the day.
The acoustic ecology of a montane forest at night
Acoustic ecology — the study of how sound shapes and reflects the biological richness of an environment — has emerged as a significant tool in conservation monitoring over the past two decades. Bernie Krause, the ecologist who pioneered the field, described the soundscape of healthy ecosystems as a complex, frequency-partitioned community where different species occupy different acoustic niches, their calls fitting together like instruments in an orchestra. A degraded ecosystem has a simplified soundscape — fewer species, less acoustic complexity, more silences.
By this measure, Bwindi at night is a profoundly healthy ecosystem. The diversity and layering of sounds in the first few hours after dark reflects the biological richness of one of Africa’s most intact ancient forests. Learning to identify even a handful of the contributors transforms an evening on the lodge terrace from a pleasant backdrop to an active encounter with the forest’s nocturnal life.
Frogs: the forest’s loudest night choir
Frogs are typically the most immediately prominent element of Bwindi’s night soundscape. Uganda hosts over 86 frog species, and Bwindi’s altitude and rainfall regime support a diverse assemblage including several Albertine Rift endemics. The most audible species begin calling at dusk and continue through much of the night, particularly around forest streams and pool margins.
The reed frogs (Hyperolius species) produce high, piping calls that carry over considerable distance. The squeaky, repetitive call of the Afromontane foam-nest frog is characteristic of forest edge environments. Deep in the forest, the ratchet-like calls of Xenopus and Nectophryne species add lower registers to the chorus. During the wet season, when breeding activity peaks, the frog chorus can be genuinely deafening — a wall of overlapping calls that makes normal conversation difficult on a rainy night at a forest lodge.
The diversity of the frog call repertoire — each species occupying a slightly different frequency range and temporal pattern — is one of the clearest demonstrations of acoustic niche partitioning in a natural system. Frogs evolved to be heard and found by conspecifics in an environment full of competing signals; the result is a system where dozens of species can simultaneously broadcast their presence without their signals being confused. Sitting quietly by a forest pool at dusk and trying to count individual frog species by call is a fascinating exercise in acoustic discrimination.
Nightjars: the forest’s night hunters
Nightjars (family Caprimulgidae) are insectivorous birds that hunt on the wing after dark, using their wide gapes to scoop moths and beetles from the air. Several species are found in the Bwindi area, including the square-tailed nightjar and the fiery-necked nightjar, whose haunting churring call is one of the characteristic sounds of sub-Saharan African forest margins at night. The fiery-necked nightjar’s song — a rising, melodic sequence sometimes rendered as “Good Lord deliver us” — is unmistakeable once learned and carries through the forest at considerable volume on still nights.
Nightjars at Bwindi are sometimes seen on night walks as pairs of glowing red eyes reflecting a torch beam from a forest road surface — they rest on the ground and roads, absorbing residual warmth from stone surfaces and hunting insects attracted to any available light source. A close view of a nightjar at rest reveals extraordinary cryptic plumage, perfectly matching dead leaves and bark, and the enormous eye that represents the primary adaptation to nocturnal vision.
Owls: the forest’s acoustic apex predators
Owls occupy the highest acoustic register in most forest night soundscapes — not the highest frequency, but the most psychologically arresting. Several owl species are present in Bwindi, including the African wood owl, Grauer’s (African) scops owl, and the remarkable Albertine owlet (Glaucidium albertinum), an Albertine Rift endemic rarely seen or recorded and among the most sought-after owl species by birders visiting the region.
The African wood owl produces a deep, resonant hooting call that many visitors initially mistake for a primate vocalization — it has a warm, almost mammalian quality that is distinctive from the higher-pitched calls of smaller owls. Scops owls produce a monotonous, single-note repetitive call that can be difficult to locate directionally, appearing to come from slightly different locations as the bird subtly adjusts its posture between calls.
Owl vocalizations are territorial and courtship signals, and their occurrence reflects the presence of mature forest territory large enough to support the prey base (small mammals, insects, frogs) that these species require. The persistence of diverse owl assemblages in Bwindi is an indirect indicator of the forest’s structural integrity — owls at the top of the food chain require a functioning ecosystem below them to sustain their populations.
Primates at night: the sounds of sleeping animals
Mountain gorillas sleep through the night in their freshly constructed nests, but they are not entirely silent. Occasional low vocalisations — the soft belch vocalisation that signals contentment — can be heard from a gorilla family’s sleeping cluster in the early evening before full darkness. This sound carries only a short distance and is most likely to be audible to guests at lodges located near the park boundary where gorilla families sometimes range very close to the forest edge.
The black-and-white colobus roar — a deep, resonant call that establishes territorial spacing between groups — is a characteristic sound of both dawn and dusk in Bwindi’s forests. Groups settling for the night often produce a sequence of roars that confirm their resting location to neighbouring groups. This sound carries over one to two kilometres through the forest and is one of the most primally impressive wildlife sounds available without leaving your lodge terrace at Buhoma or Bwindi Lodge.
Acoustic monitoring as conservation science
The night soundscape of Bwindi is not only aesthetically remarkable — it is a monitoring tool. Conservation researchers at the Institute of Tropical Forest Conservation and affiliated institutions use passive acoustic monitoring devices (remotely deployed digital recorders that run continuously and capture the full soundscape over days or weeks) to assess biodiversity without the disturbance of active surveys. Algorithms applied to the resulting recordings can detect specific species by their acoustic signatures, track changes in calling activity between seasons, and identify human disturbance events (chain saws, vehicles, firearms) that standard ranger patrols might miss.
A recording device in Bwindi’s forest captures a document of the ecosystem’s health at a specific moment in time. Over years, the acoustic record of a monitoring site becomes a time series that reveals whether species diversity is stable, improving, or declining. The night forest’s choir, in other words, is simultaneously a profound sensory experience and a scientific dataset. The beauty and the biology are the same thing.
