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Sigmodon mascotensis Allen, 1897 is a cricetid commonly called the west Mexican cotton rat. From 1902 to 1969, it was designated a subspecies of S. hispidus after which, based on chromosomal and cranial characteristics, S. mascotensis was returned to species status. Dorsal pelage is brown and hispid, with ventral areas being whitish. This Mexican endemic rodent breeds throughout the year and inhabits tropical deciduous forest zones of western Mexico, mainly associated with grassy habitats. It is rare in tropical deciduous forest and abundant in grasslands and croplands. It prefers locations with higher percentages of ground cover in woody plants, forbs, and grasses, and lower in litter and bare ground. Preference is for more open and lower canopies. It is important prey for some carnivores, birds, and reptiles. [ABSTRACT FROM AUTHOR]

In tropical deciduous forest along the Pacific coast in Colima, Mexico, we conducted eight-night mark-recapture studies of Sigmodon mascotensis (January 2003-2005), evaluating habitat preferences and demography. Yearly we established five grids with 100 trapping stations (one ground and one elevated trap; 24,000 trap-nights), each evaluated for 14 environmental measures. We captured 96 S. mascotensis 274 times on 10 grids, most at ground level (85.6%), with densities of 0.84-25.31 individuals/ha. Adults predominated (88.2%), sex ratio (males:females) was 1:0.74, and males were heavier. Sigmodon mascotensis co-occurred with Oryzomys couesi and Baiomys musculus more often and Heteromys pictus less often than chance expectation. For 2004, univariate analyses indicated that stations frequented had more ground cover in woody plants, forbs and grasses; less in litter and bare ground; more vegetation low and less high; lower and more open canopy; and longer distance to nearest tree. Logistic regression indicated preference for open canopy, dense low vegetation, little litter and longer distance to nearest tree. Nonparametric multiplicative regression showed occurrence likelihood decreased as litter increased and increased with increasing slope, average hits at 1 m and average distance to nearest tree. The likelihood was high with no or low canopy, as well as high canopy. [ABSTRACT FROM AUTHOR]

Information on geographic distribution, habitat, measurements, and reproductive condition of five species of mammals from Guerrero, Mexico, is provided. Two species are new records for the State (Nyctinomops femorosaccus and Sigmodon leucotis), one is the second record (Spermophilus variegatus variegatus), one is the third record (Nyctinomops macrotis), and one is the fourth record (Herpailurus yagouaroundi tolteca). [ABSTRACT FROM AUTHOR]

Abstract: Use of habitat is a critical component related to structure of small-mammal communities, with partitioning occurring primarily along dimensions of microhabitat, although use of microhabitat often does not explain fully use at a macrohabitat level. Through grid studies of small mammals in coastal Colima, Mexico (during January 2003–2005), we appraised influence of available habitat, species richness, abundance, and cumulative abundance of other small mammals on variation in habitat used by species. We evaluated 14 habitat variables (reflecting ground cover, slope, canopy, and vegetation density on vertical and horizontal axes) and developed a composite variable (principal component 1) reflecting general openness of habitat through which we addressed habitat use. For the four most common mammalian species (Sigmodon mascotensis, Heteromys pictus, Baiomys musculus, and Oryzomys couesi), two measures of variation in habitat used were employed to estimate niche breadth, one of which assessed variation in habitat use relative to variation present on a grid. Sigmodon mascotensis and B. musculus preferred areas that were more open, and H. pictus and O. couesi occupied less-open areas; breadth of habitat use did not differ interspecifically. Habitat use was more variable on grids with more variability in habitat, although not greater than chance expectations. Findings do not lend support to the resource-breadth hypothesis as an explanation for population densities of species at a local level or the habitat-heterogeneity hypothesis as a predictor of species richness. Variation in habitat used by S. mascotensis did not proportionally increase when diverse habitat was available but was greater when the species was more abundant. For H. pictus, when cumulative abundance of other small mammals was greater, breadth of habitat used was greater. Intraspecific density-dependent habitat selection may result in S. mascotensis selecting a greater variety of habitats, while greater interspecific abundance is related to a greater range in use of habitats by H. pictus. Baiomys musculus used a higher proportion of habitat relative to that available when more species were present on a grid. Variation in habitat used by O. couesi was unrelated to any factor examined. Overall, the four species responded in notably different ways with respect to availability of habitat, abundance, and presence of other species. [Copyright &y& Elsevier]