Keyword: ecology

Temporal segregation between two armadillo species in the southern Pantanal of Brazil

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The Pantanal of Brazil is the largest tropical wetland in the world and home to a high diversity of armadillos, with up to six sympatric species in any one location. Among these species are the nine-banded armadillo (Dasypus novemcinctus) and six-banded armadillo (Euphractus sexcinctus), both highly specialized diggers. We investigated how these two armadillos partitioned resources and coexisted by exploring multiple aspects of their ecology, including diel activity through camera trapping, and substrate and microhabitat preference through burrow sampling in forest and grassland habitats. Ultimately, we found no significant differences between the substrate particle sizes in two habitats (forest and grassland). However, because we could not confirm the relationship between burrows and species, the data obtained in the field were not sufficient to determine these correlations. We found a significant difference in activity patterns between the species, with nine-banded armadillos exhibiting greater nocturnal activity and six-banded armadillos exhibiting more diurnal activity. The species overlapped minimally overall in their activity patterns, with the highest amount of overlap occurring at dusk. Our study suggests temporal segregation occurs between these two armadillos and may serve as an ecological strategy to reduce competitive interactions between them. Future studies would benefit from assessing alternative niche axes between or among two or more armadillo species in other ecoregions.

Segregação temporal entre duas espécies de tatus no sul do Pantanal do Brasil. O Pantanal brasileiro é a maior planície alagável do mundo e apresenta alta diversidade de tatus, com seis espécies simpátricas. Dentre estas espécies estão duas de tamanho semelhante, o tatu-galinha (Dasypus novemcinctus) e o tatu-peba (Euphractus sexcinctus), ambos cavadores altamente especializados. Investigamos como essas duas espécies de tatus partilham recursos e coexistem, explorando múltiplos aspectos da ecologia das espécies, incluindo atividade diária com dados de armadilhas fotográficas e preferência de substratos e micro-habitats através da análise de tocas em ambientes de florestas e campos. Em última análise, não encontramos diferença significativa no tamanho das partículas do substrato entre os dois tipos de habitat (florestas e campos). Entretanto, como não conseguimos confirmar a relação entre tocas e espécies, os dados obtidos em campo não foram suficientes para determinar essas correlações. Encontramos diferença significativa nos padrões de atividade entre as duas espécies, com tatus-galinha exibindo mais atividade noturna, enquanto os tatus-peba exibiram mais atividade diurna. As espécies apresentaram um mínimo de sobreposição dos períodos de atividade, com a maior porção desta ocorrendo ao anoitecer. Nosso estudo sugere que a segregação temporal ocorre entre essas duas espécies de tatu e pode servir como uma estratégia ecológica para reduzir interações competitivas entre elas. Estudos futuros se beneficiariam da avaliação de eixos de nicho alternativos entre duas ou mais espécies de tatus em outras ecorregiões.

Graphical abstract for the article “Temporal segregation between two armadillo species in the southern Pantanal of Brazil” (Esparza et al., 2024)

Native and exotic small mammals as hosts of Hydatigera taeniaeformis sensu stricto larvae on pig farms of central Argentina: a study of prevalence and phylogenetic relationships

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Small mammals, including those inhabiting human-modified habitats, transmit zoonotic diseases such as cysticercosis. This disease is caused by Cysticercus fasciolaris, the larval form of species within the Hydatigera taeniaeformis s.l. group. While the life cycle of these flatworms is well understood, certain aspects of their phylogeny remain unknown. Studies in Europe, Asia, and Africa suggest that the species Hydatigera taeniaeformis s.s. exclusively infects small mammals of the family Muridae. However, no studies have been conducted in the Americas until now. In this study, small mammals were captured on 18 pig farms in the province of Buenos Aires throughout a year. Necropsies of captured individuals were performed, and the presence of cysts was recorded. The prevalence of cysticercosis was analyzed for the entire assemblage, with species as the explanatory variables. Species-specific prevalence was also modeled, considering season and type of farm as the explanatory variables. Cysts were collected from Akodon azarae, Oligoryzomys flavescens, Rattus norvegicus, and Rattus rattus, and identified through molecular techniques, comparing their DNA sequences with those stored in GenBank for phylogenetic hypothesis. A total of 460 small mammals were analyzed, including the introduced species R. norvegicus, R. rattus and M. musculus, and the native species A. azarae, O. flavescens, Oxymycterus rufus, Didelphis albiventris, and Lutreolina crassicaudata. The prevalence of cysticercosis was similar between species, and it showed a seasonal association in R. norvegicus and A. azarae. Phylogenetic analysis confirmed the presence of Hydatigera taeniaeformis s.s. in cricetids, suggesting a recent spillover event associated with European colonization in the Americas.

Pequeños mamíferos nativos y exóticos como hospedadores de larvas de Hydatigera taeniaeformis sensu stricto en granjas porcinas del centro de Argentina: estudio de su prevalencia y relaciones filogenéticas. Los pequeños mamíferos, incluidos aquellos que habitan en hábitats modificados por la especie humana, transmiten enfermedades zoonóticas como la cisticercosis. Esta enfermedad es causada por Cysticercus fasciolaris, la forma larvaria de especies pertenecientes al complejo Hydatigera taeniaeformis s.l. Aunque se conoce bien el ciclo biológico de estos platelmintos, algunos aspectos de su filogenia aún son desconocidos. Algunos estudios realizados en Europa, Asia y África sugieren que la especie Hydatigera taeniaeformis s.s. infecta exclusivamente a pequeños mamíferos de la familia Muridae. Sin embargo, hasta ahora no se habían realizado estudios en el Continente Americano. En este estudio se capturaron pequeños mamíferos en 18 granjas porcinas de la provincia de Buenos Aires a lo largo de un año. Se realizaron necropsias de los individuos capturados y se registró la presencia de cisticercos. Se calculó y modeló la prevalencia de cisticercosis para todo el ensamble, con las especies como variables explicativas. También se modeló la prevalencia especie-específica, considerando la estación y el tipo de granja como variables explicativas. Se colectaron cisticercos de Akodon azarae, Oligoryzomys flavescens, Rattus norvegicus y Rattus rattus para su análisis filogenético, y se identificaron mediante técnicas moleculares, que compararon sus secuencias de ADN con las almacenadas en GenBank. Se analizó un total de 460 pequeños mamíferos, incluidas las especies introducidas R. norvegicus, R. rattus y M. musculus, y las especies autóctonas A. azarae, O. flavescens, Oxymycterus rufus, Didelphis albiventris y Lutreolina crassicaudata. La prevalencia de cisticercosis fue similar entre especies y mostró una asociación estacional en R. norvegicus y A. azarae. El análisis filogenético confirmó la presencia de Hydatigera taeniaeformis s.s. en cricétidos, lo que sugiere un evento de spillover reciente asociado a la colonización europea de las Américas.

Graphical abstract for the article “Native and exotic small mammals as hosts of Hydatigera taeniaeformis sensu stricto larvae on pig farms of central Argentina: a study of prevalence and phylogenetic relationships” (Alonso et al., 2024)

Patrones estacionales de distribución espacial y área de acción del piche llorón, Chaetophractus vellerosus (Cingulata: Dasypodidae), en Magdalena, Buenos Aires, Argentina

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Se estimó el área de acción del armadillo Chaetophractus vellerosus y se describió su patrón espacial teniendo en cuenta la presión de uso del ambiente. Los muestreos se realizaron en un campo ganadero de Magdalena (Buenos Aires, Argentina), entre 2006 y 2011, en dos potreros de tamaño similar pero con distintas intensidades de uso (norte: baja; sur: alta). Se efectuaron 517 capturas de 213 individuos (102 machos y 111 hembras). Para determinar el área de acción se analizaron datos de 30 individuos adultos (12 machos y 18 hembras) mediante el método del mínimo polígono convexo. El patrón espacial se describió con 85 capturas y el método del vecino más cercano. No existieron diferencias significativas en el área de acción promedio entre sexos, ni entre estaciones (otoño-invierno: machos 0.23 ha, hembras 0.27 ha; primavera-verano: machos 0.75 ha, hembras 0.13 ha). Los individuos tuvieron una disposición agregada para ambos potreros en otoño-invierno, siendo mayor en el potrero de baja intensidad de uso. Durante primavera-verano en el potrero sur mantuvieron la misma distribución agregada, mientras que en el potrero norte presentaron una disposición al azar. El área de acción de C. vellerosus no se ve afectada por el sexo y las estaciones. La distribución espacial de los individuos es influenciada por la intensidad de uso del ambiente.

Spatial distribution patterns and home range of the screaming hairy armadillo, Chaetophractus vellerosus (Cingulata: Dasypodidae) in Magdalena, Buenos Aires, Argentina. The home range of the screaming hairy armadillo Chaetophractus vellerosus was estimated and its spatial pattern described under different degrees of land use pressure. Fieldwork was performed between 2006 and 2011 on a cattle ranch in Magdalena (Buenos Aires, Argentina), in two paddocks of similar size but with different intensities of use (North: low; South: high). A total of 213 individuals were captured (102 males and 111 females). Data from 30 adult individuals (12 males and 18 females) were analyzed in order to determine the home range using the minimum convex polygon method. The spatial pattern was described based on 85 captures and the nearest neighbor method. No significant differences in home range size were observed between sexes and seasons (fall-winter: males 0.23 ha, females 0.27 ha; spring-summer: males 0.75 ha, females 0.13 ha). The spatial distribution of armadillos was aggregated in both paddocks in fall-winter, being higher in the paddock with low intensity of use. An aggregated distribution was also observed during spring-summer in the southern paddock, while a random arrangement was found in the northern paddock. The home range of C. vellerosus is not affected by sex or season. The spatial arrangement of individuals is influenced by the intensity of land use.

Small mammal communities in the Sierra de los Cuchumatanes, Huehuetenango, Guatemala

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Very little is known concerning small mammal ecology and their distribution in the highlands of Guatemala. Small mammals were trapped from five different cloud forests in the Sierra de los Cuchumatanes, Huehuetenango, Guatemala. Cloud forest elevations ranged from 2600 m to 3350 m. Most sites had evidence of human disturbance, with only Cerro Bobí having a relatively pristine forest. A total of 13 species was recorded with the species density at sites ranging from six to ten. Accounts of each species are given. The most common species present was Reithrodontomys sumichrasti, except at Cerro Bobí where Peromyscus guatemalensis was most abundant. Differences between years and between seasons (wet versus dry) were minor. Only the site at Cerro Bobí, with relatively pristine cloud forest, appeared to have a species composition that resembled other cloud forests in the highlands of Guatemala. Information on reproduction is summarized.

Comunidades de pequeños mamíferos en la Sierra de los Cuchumatanes, Huehuetenango, Guatemala. Se sabe muy poco sobre la ecología y distribución de micromamíferos en las tierras altas de Guatemala. Los micromamíferos fueron capturados en cinco diferentes bosques nubosos de la Sierra de los Cuchumatanes, Huehuetenango, Guatemala. Las elevaciones de los sitios de muestreo oscilaron entre los 2600 y los 3350 m. La mayoría de los sitios tenían evidencia de perturbación humana, excepto por Cerro Bobí que tenía un bosque relativamente prístino. Se registraron 13 especies con densidad de especies entre sitios de seis a diez. Las especies más comunes presentes fueron Reithrodontomys sumichrasti, excepto en el Cerro Bobí, donde Peromyscus guatemalensis fue la especie más abundante. Las diferencias entre años y entre estaciones (húmeda versus seca) no fueron significativas. Sólo el sitio en el Cerro Bobí, con bosque nuboso relativamente prístino, parece tener una composición de especies similar a otros bosques nubosos de tierras altas de Guatemala. Adicionalmente, se presentan datos sobre las especies capturadas, incluyendo información reproductiva.

Nests of Oligoryzomys sp. and Holochilus brasiliensis (Rodentia, Cricetidae) in eastern Entre Ríos province, Argentina

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We describe the structure and location of nests built by Oligoryzomys sp. and Holochilus brasiliensis in eastern Entre Ríos Province, Argentina. Nests were associated with water bodies. Nests of Oligoryzomys sp. averaged 18 cm length, 8 cm width, and 10 cm height and were found at elevated sites, while nests of H. brasiliensis were a few centimetres above water surface and had an ellipsoid shape with a mean size of 22.5 cm length, 13 cm width, and 18.7 cm height. A seasonal nest building pattern was observed that might indicate that these species construct their nests during spring and summer for breeding. Knowing the biology of these potential pest species of economic and public health importance in a natural environment will help defining an effective control program.

Nidos de Oligoryzomys sp. y Holochilus brasiliensis (Rodentia, Cricetidae) en el este de la provincia de Entre Ríos, Argentina. Se describe la estructura y ubicación de los nidos de Oligoryzomys sp. y Holochilus brasiliensis en el este de la provincia de Entre Ríos, Argentina. Los nidos se hallaron asociados a cuerpos de agua. Los nidos de Oligoryzomys sp. se encontraron en sitios elevados; su tamaño medio fue de 18 cm de largo, 8 cm de ancho y 10 cm de alto. Los nidos de H. brasiliensis se localizaron a unos pocos centímetros sobre la superficie del agua; tenían una forma elipsoidal con medias de 22.5 cm de largo, 13 cm de ancho y 18.7 cm de alto. Se observó un patrón estacional en su construcción; esto podría indicar que estas especies construyen sus nidos durante la primavera y el verano para albergar sus crías. Estas especies tienen importancia sanitaria y económica por lo cual es importante conocer su biología en ambientes naturales para establecer un adecuado programa de control.

Dinâmica populacional de marsupiais e roedores no Parque Municipal da Lagoa do Peri, Ilha de Santa Catarina, sul do Brasil

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Population dynamics of marsupials and rodents in Parque Municipal da Lagoa do Peri, Santa Catarina Island, southern Brazil. A two-year mark-recapture study of small mammals was conducted in an area of Atlantic Forest hillside in the state of Santa Catarina, Brazil. Four species of marsupial and seven species of rodent were captured during 12132 trap nights. Aspects of population dynamics and natural history are discussed for each common species. The sex ratio was biased toward males for all species. Oryzomys russatus, Didelphis aurita and Akodon montensis had the highest population densities, the least amount of variation in population density and an inverse relationship between survivorship rates and population densities. Micoureus paraguayanus, Nectomys squamipes and O. angouya registered the higher population densities after continual survivorship rates. The recruitment rates were low for most species (< 50%), with some, M. paraguayanus, Lutreolina crassicaudata, Oligoryzomys nigripes, O. angouya and Oxymycterus aff. judex, disappearing occasionally from the study area. The survivorship rates were high for most species (> 50%). Population densities of D. aurita, O. nigripes and O. aff. judex increased in cold and dry periods. The marsupials reproduced seasonally from late winter until the end of the summer, whereas rodents reproduced throughout the year. No species were long-lived, with average life-span < six months.

Parameters modeling speciogenic processes in Cebus apella (Primates: Platyrrhini) from Argentina

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In the last fifteen years the phylogenies of New World Primates (NWP) have been reviewed. Genetic tools, ranging from traditional cytogenetics to modern DNA analysis, are very powerful sources of information. However, little can be said regarding the speciogenic process of a given species without a complement of biogeography and traditional taxonomy. Within Argentina there are two reported subspecies of Cebus apella, popularly known as tufted capuchin monkeys: Cebus apella paraguayanus, from Salta and Jujuy, and C. a. nigritus, inhabiting the Paranaense forest in northern Misiones. This contribution intends to review a series of variables in order to discuss possible evolutionary pathways of tufted capuchins’ speciation in Argentina considering the hypothesis of the distinct biogeographical origin for these subspecies. A morphometric analysis using 30 cranial and dental measurements gives significant differentiation among subspecies (p < 0.0001). Data from heterochromatic polymorphisms supports an active speciation process, reflected in the gradual loss of the large heterochromatic segment of pair 11. Genetic distance employing the COII gene with only transversional substitutions, finds a divergence greater (dTN = 0.0072) than in interspecific comparisons within other genera. The reconstruction of the evolutionary history of Cebus apella, within the particular characteristics of its southernmost distribution in Argentina and neighboring countries, is attempted.

Parámetros que modelarían la especiogénesis de Cebus apella (Primates: Platyrrhini) de Argentina. Las filogenias de los Primates del Nuevo Mundo han sido revisadas exhaustivamente en los últimos 15 años. Las herramientas genéticas, desde la citogenética clásica hasta los modernos análisis de ADN, se consideran grandes fuentes de información filogenética. Sin embargo, poco puede decirse acerca de la especiogénesis de una especie determinada sin incluir información biogeográfica y de taxonomía tradicional. En la Argentina existen dos subespecies del mono capuchino con penacho, Cebus apella: C. a. paraguayanus, de Salta y Jujuy, y C.a. nigritus, de la selva Paranaense de Misiones. Este trabajo intenta revisar una serie de variables para discutir posibles caminos evolutivos que separaron a estas subespecies de su ancestro común, considerando un posible origen biogeográfico distinto. Un análisis morfométrico empleando 30 medidas craneanas y dentarias permitió separar ambas subespecies (p < 0.0001). El estudio de la heterocromatina apoya un proceso activo de especiación, reflejado en la pérdida gradual de la porción heterocromática distal del cromosoma 11. La distancia genética, calculada a partir de las transversiones para el gen mitocondrial COII sugiere una diferenciación mayor (dTN = 0.0072) que la obtenida para comparaciones interespecíficas en otros géneros. Se propone una reconstrucción de la historia evolutiva de Cebus apella, dentro de los límites de su distribución marginal sur, en Argentina y países vecinos.