It also occurs throughout northern Colombia at low elevations and into western Venezuela west of Lake Maracaibo and at the foot of the western part of the Venezuelan Coastal Range east to Guatopo National Park. Hylaeamys megacephalus occurs further to the east in the eastern portion of the coastal range, separated by the coastal Eastern Caribbean Dry Zone. There is a record from the Orinoco Delta of northeastern Venezuela, well within the range of Hylaeamys megacephalus, but Musser and colleagues suggest that this is based on mislabeled specimens. The species has also been found on the narrow strip between the Llanos and the Andes (Cordillera Oriental and Cordillera de Mérida) in eastern Colombia and northwestern Venezuela. The unforested Llanos separate these areas from Hylaeamys populations. Hylaeamys perenensis does, however, occur further south along the eastern foothills of the Cordillera Oriental in Colombia and it is possible that the two overlap in this area.