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A checklist of the family Trombiculidae and Leeuwenhoekiidae is presented, containing 63 species in 30 genera of chiggers from 80 different hosts and 146 localities in Brazil. The type locality and depository are provided, including new locality and host records for the country.

Abstract Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates, invertebrates, and plant matter. While cranium and scapula variation has already been examined within Didelphidae, variation in mandible shape, usually associated with diet or phylogeny in other mammalian groups, has not yet been properly assessed in the family. We evaluated the variation in mandible shape and size of didelphids (2470 specimens belonging to 94 species) using 2D geometric morphometrics. We classified the diet of the didelphids into four broad categories to assess whether morphospace ordination relates to dietary habits. We also provided the most comprehensive phylogeny for the family (123 out of the 126 living species) using 10 nuclear and mitochondrial genes. We then mapped mandible size and shape onto that phylogeny for 93 selected taxa and ancestral size and shapes were reconstructed by parsimony. We found phylogenetically structured variation in mandible morphology between didelphid groups, and our results indicate that they have a significant phylogenetic signal. The main axis of shape variation is poorly related to size, but the second is strongly allometric, indicating that allometry is not the main factor in shaping morphological diversity on their mandibles. Our results indicate that the shape and size of the ancestral mandible of didelphids would be similar to that of the current species of the genus Marmosa.

The growing proximity of wildlife to large urban niches arouses greater interest in understanding wild reservoirs in the epidemiology of diseases of importance to animal and human health. The aim of the present study was to investigate the presence of piroplasmids in opossums rescued from the metropolitan region of Rio de Janeiro state, Brazil. Blood and bone marrow samples were collected from 15 Didelphis aurita and subjected to DNA extraction and PCR using primers for the 18S rRNA, cox1 , cox3 , and hsp70 genes of piroplasmids. Clinical and hematological evaluation of the animals was also performed. Five (33.3%) of the 15 opossums tested positive for piroplasms in the nested PCR based on the 18S rRNA, and in two animals, it was possible to observe intra-erythrocytic structures compatible with merozoites. One of the positive animals showed clinical signs of infection such as jaundice, fever, and apathy. Anemia, low level of plasma protein, leukocytosis, and regenerative erythrocyte signs were observed in positive animals. Phylogenetic analysis based on both 18S rRNA and cox-3 genes demonstrated that the piroplasmids detected in D. aurita formed a unique sub-clade, albeit related to piroplasmids previously detected in Didelphis albiventris and associated ticks from Brazil. This study proposes the novel Piroplasmida Clade, namely “South American Marsupialia Group,” and reinforces the need for new clinical-epidemiological surveys to understand the dynamics of these infections in didelphids in Brazil.

Tropical rainforests support the greatest diversity of small mammals in the world, yet we have little understanding about the mechanisms that promote the coexistence of species. Diet partitioning can favor coexistence by lessening competition, and interspecific differences in body size and habitat use are usually proposed to be associated with trophic divergence. However, the use of classic dietary methods (e.g. stomach contents) is challenging in small mammals, particularly in community-level studies, thus we used stable isotopes (δ13C and δ15N) to infer about trophic niche. We investigated i) how trophic niche is partitioned among rodent and marsupial species in three Atlantic forest sites and ii) if interspecific body size and locomotor habit inequalities can constitute mechanisms underlying the isotopic niche partitioning. We found that rodents occupied a broad isotopic niche space with species distributed in different trophic levels and relying on diverse basal carbon sources (C3 and C4 plants). Surprisingly, on the other hand, marsupials showed a narrow isotopic niche, both in δ13C and δ15N dimensions, which is partially overlapped with rodents, contradicting their description as omnivores and generalists proposed classic dietary studies. Although body mass differences did not explained the divergence in isotopic values among species, groups of species with different locomotor habit presented clear differences in the position of the isotopic niche space, indicating that the use of different forest strata can favor trophic niche partitioning in small mammals communities. We suggest that anthropogenic impacts, such as habitat modification (logging, harvesting), can simplify the vertical structure of ecosystems and collapse the diversity of basal resources, which might affect negatively small mammals communities in Atlantic forests.

The bushy-tailed opossum (Glironia venusta) is a small arboreal marsupial found in the Amazon basin. G. venusta is rarely seen and has few published sightings throughout its range. Videos (N = 79) were obtained from arboreal camera traps located in the Las Piedras Amazon Center near the Las Piedras River (SE Peru) from April 2017 until November 2017. Our new records, the first for the Las Piedras River, demonstrate that the species is nocturnal with activity peaks at 3:00 h and 20:00 h in the hours of complete darkness. The abundance of camera trap footage of such a rarely observed species further demonstrates the effectiveness of arboreal camera trapping to conduct species assessments.

Anthropogenic activities since the European colonization of the North American Great Plains have drastically altered landscape composition and configuration, subsequently affecting native biodiversity. These contemporary human-modified landscapes may affect mammal species’ distributions, diel activity patterns, habitat use, and interspecific interactions, though a better understanding of these effects on mammals occurring in remaining prairie landscapes is needed. To fill this gap, we surveyed 381 randomly selected sites in 2018, 2019, and 2020 using motion-sensing camera traps across the western part of the US state of Kansas (7,160,077 ha). Sites were separated by ≥2 km (x = 8.16 km, SD = 3.61), and cameras were secured to a metal post 40 cm above ground and randomly oriented toward the north or south. We placed an olfactory attractant (mixture of skunk essence and petroleum jelly) on a wooden stake 3 m in front of each camera. Cameras were in place at each site for 28 consecutive days for each year. We manually identified all mammal species detected at each site, collating these data into a database that included taxonomic information for 14 families of mammals (Antilocapridae, Bovidae, Canidae, Cervidae, Cricetidae, Dasypodidae, Didelphidae, Erethizontidae, Felidae, Heteromyidae, Leporidae, Mephitidae, Mustelidae, Procyonidae, Sciuridae, and Muridae) comprising 28 total species. We recorded 31,178 mammal photographs (nonindependent events) over 27,954 camera trap nights during 2018 (n = 10,351), 2019 (n = 9478), and 2020 (n = 8125). Additionally, we included the time and date of each photocapture. Moreover, we gathered survey-specific data useful for modeling species-specific detection along with site-level habitat composition data taken at each site each year. These data will be useful for examining habitat use, species distributions, diel activity patterns, and spatiotemporal interactions between species and across guilds of mammals occurring in a rapidly changing agro-prairie ecosystem. There are no copyright restrictions, but we ask researchers to cite this paper when using these data for publication.

Phylogenetic analysis of a fragment of the mitochondrial genome and qualitative and quantitative assessments of morphological variation suggest that, in its current conception, Thylamys pusillus (Desmarest, 1804) is a complex of at least three species. In the taxonomic arrangement proposed in this work, the populations in the Argentinean provinces of Entre Rios and Corrientes are here referred to T. citellus (Thomas, 1912), while the small Thylamys that lives in the Argentinean Dry Chaco are provisionally referred to T. pulchellus (Cabrera, 1934). In our scheme, Thylamys pusillus is restricted to the Bolivian and Paraguayan Chaco and the vicinities of northern Formosa province in Argentina. We provide emended diagnosis for T. citellus and T. pulchellus, together with detailed morphological descriptions and discuss their distinctiveness from other species of Thylamys. In addition, we included new distributional data.Original Abstract: El analisis filogenetico de un fragmento del genoma y el estudio cualitativo y cuantitativo de la morfologia externa y craneana sugiere que, en su actual acepcion, Thylamys pusillus (Desmarest, 1804) es un complejo de por lo menos tres especies. En el arreglo taxonomico propuesto en este trabajo, las poblaciones en las provincias argentinas de Entre Rios y Corrientes son referidas como T. citellus (Thomas, 1912), mientras que una forma pequena de Thylamys que habita en el Chaco Seco de Argentina es provisoriamente referida como T. pulchellus (Cabrera, 1934). En este esquema, la distribucion de Thylamys pusillus es restringida al Chaco de Bolivia, Paraguay y areas adyacentes de Argentina en el nordeste de la provincia de Formosa. Se proveen diagnosis enmendadas para T. citellus y T. pulchellus, conjuntamente con una detallada descripcion morfologica de ambas entidades y una discusion de las diferencias con otras especies de Thylamys. Por ultimo, se incluyen nuevos datos de distribucion.

The marsupials of Mato Grosso do Sul (MS) state in southwestern Brazil are still poorly known, with most research being concentrated around the Pantanal wetland. In this work, the marsupial richness was analysed in four different ecoregions of MS, based on more than ten years of sampling using live and pitfall traps, comparing them with published information. Fifteen marsupial species were recorded, adding 117 new records and increasing the previously known richness by more than 50%. These new records represent an increase between 96.7% ( Gracilinanus agilis ) to 9.1% ( Chironectes minimus ) of those previously known for the state, with an average increase of 43%. Cryptonanus agricolai is recorded for the first time for MS, but we did not trap Caluromys lanatus and Metachirus myosuros , which were mentioned in the literature. The Cerrado ecoregion (a type of savanna) shows more species than other ecoregions, being the largest ecoregion in the state. A strong faunal turnover was found in the state, from the humid and mild forests of the southeast (Atlantic forest ecoregion) to the more seasonal, dry, and warm forests, shrublands, and grasslands of the northwest (Chiquitano and Pantanal ecoregions). A full taxonomic account and localities of the species recorded are provided and the biogeographical affinities of ecoregions present in MS are discussed.

Small mammal assemblages from South America provide a unique opportunity to measure coexistence and niche partitioning between marsupials and placentals. We tested how these two major clades partition environmental resources by comparing stable isotopic ratios of similar sized Didelphidae and Sigmodontinae in four Brazilian biomes: Pampas grassland, Pantanal wetland, Cerrado woodland savanna, and Atlantic Forest. Generally, didelphid isotopic niche follows a scaling law, because we found an association between δ15N enrichment and body mass. Sigmodontines that primarily partition the environment via forest strata showed a greater intake of C4 or/and crassulacean acid metabolism (CAM) plants than didelphids, as reflected by their wider trophic niche. Values of δ13C were highest in savannas and grasslands (Cerrado and Pampas biomes), and values of δ15N were highest in the Atlantic Forest (in sigmodontines) and Pampas (in didelphids). While assessing patterns between the two major Brazilian biomes (Atlantic Forest and Cerrado), we found evidence of a broader trophic niche for both clades in the Cerrado. In the Atlantic Forest, niche occupation by Didelphidae was completely enclosed within the Sigmodontinae trophic niche. Both clades showed less overlap in the Cerrado, a less productive environment. Our results highlight the importance of a comparative framework and the use of stable isotopes for testing ecological questions related to how small mammalian communities partition their niche.

Background Efficacy studies are part of the regulatory requirements for obtaining marketing authorization for rabies virus vaccines intended for veterinary use. However, increasing emphasis on animal welfare and the application of the 3Rs principles (Replacement, Reduction, and Refinement) may prompt a critical reassessment of current standards for such studies. A substantial amount of data from numerous published experimental studies is available, which could be used to reconsider or refine existing specifications and protocols—particularly concerning observation periods post-infection (pi) and dose-finding studies. Methods To support this reassessment, we analyzed data from 289 published experimental studies. These studies covered both susceptibility and efficacy investigations across 16 mesocarnivorous target species considered for parenteral or oral rabies vaccination. The species represented seven taxonomic families or orders: Canidae, Didelphidae, Felidae, Herpestidae, Mephitidae, Musteloidea, and Procyonidae. The dataset included 1,171 records encompassing a total of 8,381 animals that had been vaccinated with either rabies virus (RABV) or non-RABV lyssaviruses. Parametric distributions (log-normal, Weibull, and gamma) were fitted to incubation periods to examine group differences. Additionally, multiple linear and logistic regression analyses were performed to identify key variables influencing incubation duration, post-infection survival, and inter-species differences among reservoir hosts. Results The analyses revealed that viral strain, inoculation dose, and application site were consistently associated with incubation period length and mortality across most taxonomic groups. These variables significantly influenced incubation periods and survival rates post-infection. Notable differences were also observed between reservoir host species, highlighting the importance of species-specific factors in study design and interpretation. Conclusions Our findings suggest that, in alignment with the 3Rs principle, existing animal models used in rabies vaccine efficacy research can be reconsidered and potentially refined. These refinements may not only enhance scientific validity but also contribute to ethical improvements in study design. Furthermore, the results may inform future risk assessments related to the importation of pets from rabies-endemic regions and support more humane, evidence-based approaches to vaccine evaluation.