Sapo contains one of the most important remaining populations of African forest elephant (Loxodonta cyclotis) in Liberia and one of the few significant populations in West Africa as a whole. The species is smaller and rounder-eared than the savanna elephant, with straighter tusks, and it is critically endangered across its range.
Forest elephants in Sapo are mostly inferred from sign — dung piles, footprints in muddy game trails, broken vegetation at fruiting trees, and the distinctive low rumbles that occasionally drift through the forest. Sightings are very rare and treated with caution; an unhabituated forest elephant at close range is dangerous. Rangers are trained to recognise sign and move groups away from likely points of contact.