Antonio Utrera

Small Mammals in Agricultural Areas of the Western Llanos of Venezuela: Community Structure, Habitat Associations, and Relative Densities

Abstract We used mark–recapture and removal trapping during 37 months to examine structure of small-mammal assemblages in agricultural and pastoral areas on the western llanos of Venezuela. Among 34 sites sampled, species richness, diversity, population densities, and relative contribution to the assemblage by 10 rodent and 3 marsupial species varied by habitat or land-use category, major vegetative formation, and (within agricultural systems) crop species. Most habitat types, especially relatively uniform areas of mechanized agriculture, were numerically dominated by 2 rodents, Sigmodon alstoni and Zygodontomys brevicauda. Subsistence agriculture plots were more variable and had the highest species richness and diversity. Peridomestic habitats were dominated by Rattus rattus. In contrast to findings in agroecosystems in the United States and Argentina, relative densities were not lower in crop fields than in adjacent borders nor were there differences in the structure of the rodent assemblages. Captures of Heteromys anomalus, Oecomys speciosus, and Oecomys trinitatus document range extensions for these species on the western llanos.

The Delicate Pygmy Rice Rat (Oligoryzomys delicatus) Is the Principal Host of Maporal Virus (Family Bunyaviridae, Genus Hantavirus)

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.

Transmission of Guanarito and Pirital Viruses among Wild Rodents, Venezuela

Secretions and excretions from virus-infected cane mice and cotton rats might transmit disease to humans.

Natural Host Relationships of Hantaviruses Native to Western Venezuela

Strains of Caño Delgadito virus (CADV) and Maporal virus (MAPV) were isolated from 25 (8.9%) of the 280 rodents captured on farms in 1997 in western Venezuela. The results of analyses of laboratory and zoographic data indicated that Alstons cotton rat (Sigmodon alstoni) is the principal host of CADV, horizontal virus transmission is the dominant mode of CADV transmission in Alstons cotton rat in nature, a pygmy rice rat (Oligoryzomys sp.) is the principal host of MAPV, and the natural host relationships of CADV and MAPV are highly specific.