A distinctive species characterized by very large body size and four pairs of teats (pectoral, postaxillary, and two inguinal). Treated as a species by Hill and Carter (1941) and Ellerman et al. (1953), but synonymized with S. pratensis by Coetzee (1977a) and listed that way in most contemporary faunal accounts. Crawford-Cabral (1998) recognized the specific integrity of bocagei, and explained that it has only four pairs of teats in contrast to S. pratensis with five pairs (sometimes more; see Coetzee, 1977a). That distinguishing trait, its very large body size compared to S. pratensis from southern and eastern Africa, and study of the large series reported by Hill and Carter (1941) identify a species separate from S. pratensis or the large-bodied S. opimus.

Crawford-Cabral identified the large-bodied Steatomys from NE Angola as S. pratensis kasaicus (teat number not counted); Coetzee (1977a), however, included kasaicus in bocagei, the correct allocation. Skins in the type series of kasaicus (AMNH 85073, 86080) possess only four pairs of teats; this pattern, their large body and cranial dimensions, and geographic continuity with Angolan populations attest to their identification as S. bocagei. Coetzee claimed intergradation between bocagei and pratensis in the Katanga region of E Dem. Rep. Congo, but no published data supports that contention. Furthermore, typical S. pratensis has been collected in S Angola and those examples exhibit no trace of morphological intergradation with S. bocagei. Relationship with the other large-bodied species of Steatomys—S. jacksoni from West Africa, number of teats unknown; or S. opimus from northern savannas, five or more pairs of teats—awaits resolution. Rosevear (1969) regarded West African S. jacksoni to closely resemble S. bocagei in body size and pelage coloration.