Choclo virus (CHOV) and Maporal virus (MAPV) are enzootic in Panama and western Venezuela, respectively. The results of previous studies suggested that the fulvous pygmy rice rat (Oligoryzomys fulvescens) is the principal host of both viruses. The results of an analysis of nucleotide sequence data in this study indicated that the rodent associated with CHOV is the Costa Rican pygmy rice rat (Oligoryzomys costaricensis) and that the rodent associated with MAPV is the delicate pygmy rice rat (Oligoryzomys delicatus). As such, MAPV is ecologically distinct from CHOV and should be considered a species separate from CHOV.