Members of the genus Oncicola Travassos, 1916 are generalist parasites able to infect a broad spectrum of carnivorous hosts, such as marsupials, procyonids, felids, and canids, and are distributed globally. Adult specimens were collected from the intestines of three white-nosed coatis (N. narica), whereas cystacanths (larval form) were found in the body cavities of two amphibian species (paratenic hosts) in localities from northern and southeastern Mexico. Morphologically, both stages were identified as O. luehei (Travassos, 1917) on the basis of the following features: trunk cylindrical, narrow anteriorly, enlarging midbody, tapering gradually to narrow posteriorly; proboscis globular with six circular rows of hooks with six hooks each, decreasing in size posteriorly; neck short with sensory papilla; tubular lemnisci long, extending to the posterior region; protonephridia dendritic type; and eight cement glands, compact with a single giant nuclei. Sequences from cytochrome c oxidase subunit 1 from mtDNA were aligned and compared with sequences available in GenBank. Phylogenetic analyses revealed that adults and cystacanths formed a clade with two other isolates identified as Oncicola sp. and O. luehei from Mexico. The intraspecific genetic divergence among the isolates was low, ranging from 0.0% to 3.0%, indicating that the two stages of the life cycle belong to the same species. The haplotype network was inferred with 11 sequences and revealed a lack of shared haplotypes between populations, suggesting a reduced recombination rate and a high pattern of genetic variation among individuals. Finally, these new records of O. luehei increase the distribution range of O. luehei on both coasts of Mexico.

Dung beetles attracted to howler monkey (Alouatta palliata) and coati (Nasua narica) dung were studied for an annual cycle in the tropical rain forest of Los Tuxtlas, Mexico. Pitfall traps set for 24 h month−1 captured 1567 dung beetles of 21 species. The species Canlhidium martinto, Deltochilum pseudoparile and Canthon femoralis accounted for 62% of all individuals captured. While species overlap was high (> 80%) between diurnal and nocturnal samples and between howler monkey and coati dung baits, coati dung attracted species such as C. martinezi, D. pseudoparile and Onthophagus rhinolophus while species such as C. femoralis and Copris laeviceps were numerically dominant at howler monkey dung. Thirteen non-ball rolling dung beetle species and eight ball-rolling species accounted for 43% and for 57% of all beetles captured respectively. Dung beetles were present and active in all months of the year, but occurred in higher numbers between the months of March and October, when temperatures were higher. Relative abundance of howler monkey and coati dung in the rain forest of Los Tuxtlas was estimated at 11.2 g (fresh weight) ha−1 day−1 and at 13.0 g ha−1 day−1 respectively, a seemingly low amount for the large number of scarabs attracted to the dung.

Interactions between sympatric species are of particular interest for understanding the mechanisms that allow animal coexistence in the ecological community. The mantled howler monkey (Alouatta palliata Gray) and the white-nosed coati (Nasua narica Linnaeus) are similar-sized mammals with a sympatric distribution in the Neotropics (Nowak 1999). Since these two species are partly frugivorous (howler, Crockett & Eisenberg 1987; coati, Gompper 1997), and fruit is often limited (Laurance et al. 2003), howlers and coatis might be observed foraging from the same fruiting tree, but there is no information regarding this possibility. We studied the feeding encounters between these two species in a small forest fragment, and discuss the conditions under which these episodes occur.

The mating system displayed by a species or population is a complex result of interactions among many factors, including social organization and resource distribution. Lekking is rare among mammals, and despite decades of research and theoretical debate, there is still little agreement concerning the socio-ecological conditions that give rise to this mating system. This study documents a lek-like mating system in a population of white-nosed coatis Nasua narica: the first such system observed in a carnivore species. Male coatis in Tikal National Park, Guatemala, aggregated around mobile bands of females during the mating season. The males displayed from the forest canopy above the bands, and females ascended to a male's perch when they were ready to mate. Males did not provide resources or parental care. Thus, the mating system, which differed from classic lekking only in the lack of an arena, can be best described as mobile lekking. Male coatis apparently resort to self-advertisement when the large size and large home ranges of female groups make defence of females or resources impractical.

The resource dispersion hypothesis (RDH) proposes that in a spatially and temporally heterogeneous environment the territory size of social carnivores increases as the dispersion of limited resources is more widely spaced, whereas group size is limited, independently, by the richness or abundance of those resources or key habitats. To assess if white-nosed coatis Nasua narica behave in accordance with the RDH, the relationship between home-range size and spatio-temporal availability of resources in Mexican tropical dry forests with marked seasonal rainfall was examined. Specifically, home-range sizes were compared at two study sites that were broadly similar but contrasting in resource abundance and dispersion. Home-range estimates for seven white-nosed coati bands varied between 45 and 362 ha. Home-range size did not correlate with food resource abundance and was better explained by the dispersion of water sources during the dry season. Average home-range size was three times greater at the site where water sources were more widely separated during the dry season. These results are in accordance with the predictions of the RDH, and provide an example where the critical resource determining range size and configuration is water.