Journal of Zoology, 2016; 300: 305-313The black and rufous sengi Rhynchocyon petersi is restricted to the Eastern ArcMountains and coastal forests of East Africa and considered vulnerable because ofhabitat fragmentation and degradation. Coastal forests are believed to have beenisolated from each other for thousands of years due to climatic changes. SinceR. petersi is described as strongly dependent on its forest habitat, we hypothesizedthat R. petersi from different forests would show genetic divergence. We investi-gated the genetic structure and diversity of this species in four coastal forests inTanzania using eight microsatellites and cytochrome b sequences. In total, 45 indi-viduals were captured after strenuous sampling efforts. For comparative purposeswe also sequenced the cytochrome b of 57 individuals from a sympatric rodent for-est species, Beamys hindei. The results indicate extant R. petersi have descendedfrom a single population of high effective size (Ne) with no forest-distinctive sig-nal. In contrast, B. hindei is more genetically structured: Although the most com-mon haplotype is found in the three closest forests, each forest harbours privatehaplotypes. Moreover, B. hindei Ne appeared 10 times smaller than R. petersi inZaraninge forest. While B. hindei results are consistent with the scenario of long-term isolation of coastal forests, the R. petersi are not. We suggest R. petersi mayless depend on forest habitat than previously suspected, consistent with anecdotalreports of sengis nesting in intervening agricultural habitat. From a conservationviewpoint, this sengi species therefore appears robust to the current spatial andtemporal scale of habitat fragmentation.