RESUMO

The aim of this work was to obtain the first estimates of survival rates (S), capture probability (p) and life expectancy for armadillos in South America by analyzing capture-mark-recapture data obtained from a population of Chaetophractus vellerosus (Gray, 1865) located in Magdalena, Buenos Aires, Argentina. From June 2006 to June 2011, we conducted 16 field surveys that resulted in 365 capture events of 152 adult C. vellerosus. For the survival analysis we used a Cormack-Jolly-Seber (CJS) modelling framework. Interannual variation in S made an important contribution to overall variation in the survival rate of C. vellerosus. The average life expectancy for females and males after attaining sexual maturity was estimated at 1.70 and 1.65 years respectively. The period of lowest survival probability was associated with dry seasons that might have affected the availability of food. This study provides the first estimates of demographic parameters for xenarthrans in South America.

Assuntos

RESUMO

The aim of this work was to obtain the first estimates of survival rates (S), capture probability (p) and life expectancy for armadillos in South America by analyzing capture-mark-recapture data obtained from a population of Chaetophractus vellerosus (Gray, 1865) located in Magdalena, Buenos Aires, Argentina. From June 2006 to June 2011, we conducted 16 field surveys that resulted in 365 capture events of 152 adult C. vellerosus. For the survival analysis we used a Cormack-Jolly-Seber (CJS) modelling framework. Interannual variation in S made an important contribution to overall variation in the survival rate of C. vellerosus. The average life expectancy for females and males after attaining sexual maturity was estimated at 1.70 and 1.65 years respectively. The period of lowest survival probability was associated with dry seasons that might have affected the availability of food. This study provides the first estimates of demographic parameters for xenarthrans in South America.(AU)

Assuntos

RESUMO

Se estudiaron las características morfológicas de la mandíbula de adultos de Chaetophractus vellerosus (Gray, 1865) y Zaedyus pichiy (Desmarest, 1804), a fin de establecer su diseño generalizado y de identificar diferencias inter e intraespecíficas. Las descripciones morfológicas se complementaron con técnicas univariadas y multivariadas (análisis de matrices de correlación, ACP, análisis discriminante). La mandíbula es similar en ambas especies, y se caracteriza por cóndilo elevado, proceso angular bien desarrollado, proceso coronoides pronunciado, hilera dentaria que se extiende hasta el ángulo mandibular, y sínfisis no fusionada pero firme. La mandíbula de Z. pichiy es más esbelta y delicada que la de C. vellerosus, lo que podría indicar mayor adaptación del primero a hábitos insectívoros, a pesar de la omnivoría general en la que incursionan ambas especies. El ACP permitió observar una segregación casi total de las dos especies sobre CP1 (47,7% de la varianza total), con C. vellerosus asociado a mayores valores de ancho de rama ascendente, ancho de rama horizontal y altura mandibular. Zaedyus pichiy se asoció a valores elevados de longitud mandibular sobre CP2 (22,6% de la varianza). El dimorfismo sexual es leve en ambas especies; en C. vellerosus quedó definido por un factor tamaño, con mandíbulas mayores en las hembras, mientras que en Z. pichiy se verificaron diferencias de forma, con mandíbulas más altas en los machos y más largas en las hembras. Las correlaciones entre variables fueron más elevadas en los machos que en las hembras de ambas especies, indicando una mayor estabilidad en la forma mandibular de los primeros. Los parámetros seleccionados para la discriminación sexual fueron la longitud del cuerpo mandibular en C. vellerosus (aproximadamente 86% de clasificación correcta en machos, 81% en hembras), y la altura a nivel del último molariforme en Z. pichiy (cerca de 85% de clasificación correcta en ambos sexos)...

The morphological characteristics of the mandible of adult Chaetophractus vellerosus (Gray, 1865) and Zaedyus pichiy (Desmarest, 1804) were studied to establish its generalized design and to identify inter- and intra- (sexual) specific differences. Morphological descriptions were complemented with the application of univariate and multivariate (analysis of correlation matrices, PCA, discriminant analysis) techniques. The mandible of both species is very similar, and is characterized by elevated condyle, well developed angular process, distinct coronoid process, tooth row which extends to the rear end of the angle between body and ramus, and unfused but firm symphysis. Although both armadillos are omnivorous, a more slender configuration of the jaw in Z. pichiy could be indicative of a better adaptation of its masticatory apparatus to insectivory. The PCA showed an almost total segregation of both species on PC1 (47.7% of the total variance), with C. vellerosus being associated to mandibles taller and with wider body and ramus. Zaedyus pichiy was characterized by heavy loadings of length parameters on PC2 (22.6% of the variance). A small degree of sexual dimorphism was found, with size-based differences in C. vellerosus (larger mandibles in females) and shape-based differences in Z. pichiy (taller mandibles in males, longer ones in females). Correlations between variables were higher in males of both species, indicating a more stable shape of the mandible than in females. The selected parameters to discriminate sexes were the body length of the mandible in C. vellerosus (correct classification: ca. 86% in males, 81% in females), and the height of the mandible at the level of the last tooth in Z. pichiy (near 85% of right assignment in both sexes). The inclusion of a new variable (body length) in the latter species improved the classification of the females to 100%...

Assuntos

RESUMO

Se estudiaron las características morfológicas de la mandíbula de adultos de Chaetophractus vellerosus (Gray, 1865) y Zaedyus pichiy (Desmarest, 1804), a fin de establecer su diseño generalizado y de identificar diferencias inter e intraespecíficas. Las descripciones morfológicas se complementaron con técnicas univariadas y multivariadas (análisis de matrices de correlación, ACP, análisis discriminante). La mandíbula es similar en ambas especies, y se caracteriza por cóndilo elevado, proceso angular bien desarrollado, proceso coronoides pronunciado, hilera dentaria que se extiende hasta el ángulo mandibular, y sínfisis no fusionada pero firme. La mandíbula de Z. pichiy es más esbelta y delicada que la de C. vellerosus, lo que podría indicar mayor adaptación del primero a hábitos insectívoros, a pesar de la omnivoría general en la que incursionan ambas especies. El ACP permitió observar una segregación casi total de las dos especies sobre CP1 (47,7% de la varianza total), con C. vellerosus asociado a mayores valores de ancho de rama ascendente, ancho de rama horizontal y altura mandibular. Zaedyus pichiy se asoció a valores elevados de longitud mandibular sobre CP2 (22,6% de la varianza). El dimorfismo sexual es leve en ambas especies; en C. vellerosus quedó definido por un factor tamaño, con mandíbulas mayores en las hembras, mientras que en Z. pichiy se verificaron diferencias de forma, con mandíbulas más altas en los machos y más largas en las hembras. Las correlaciones entre variables fueron más elevadas en los machos que en las hembras de ambas especies, indicando una mayor estabilidad en la forma mandibular de los primeros. Los parámetros seleccionados para la discriminación sexual fueron la longitud del cuerpo mandibular en C. vellerosus (aproximadamente 86% de clasificación correcta en machos, 81% en hembras), y la altura a nivel del último molariforme en Z. pichiy (cerca de 85% de clasificación correcta en ambos sexos)...(AU)

The morphological characteristics of the mandible of adult Chaetophractus vellerosus (Gray, 1865) and Zaedyus pichiy (Desmarest, 1804) were studied to establish its generalized design and to identify inter- and intra- (sexual) specific differences. Morphological descriptions were complemented with the application of univariate and multivariate (analysis of correlation matrices, PCA, discriminant analysis) techniques. The mandible of both species is very similar, and is characterized by elevated condyle, well developed angular process, distinct coronoid process, tooth row which extends to the rear end of the angle between body and ramus, and unfused but firm symphysis. Although both armadillos are omnivorous, a more slender configuration of the jaw in Z. pichiy could be indicative of a better adaptation of its masticatory apparatus to insectivory. The PCA showed an almost total segregation of both species on PC1 (47.7% of the total variance), with C. vellerosus being associated to mandibles taller and with wider body and ramus. Zaedyus pichiy was characterized by heavy loadings of length parameters on PC2 (22.6% of the variance). A small degree of sexual dimorphism was found, with size-based differences in C. vellerosus (larger mandibles in females) and shape-based differences in Z. pichiy (taller mandibles in males, longer ones in females). Correlations between variables were higher in males of both species, indicating a more stable shape of the mandible than in females. The selected parameters to discriminate sexes were the body length of the mandible in C. vellerosus (correct classification: ca. 86% in males, 81% in females), and the height of the mandible at the level of the last tooth in Z. pichiy (near 85% of right assignment in both sexes). The inclusion of a new variable (body length) in the latter species improved the classification of the females to 100%...(AU)

Assuntos