Agustina Novillo

The exotic mammals of Argentina

Exotic mammals in South America represent about 20% of world mammal introductions. The aim of our paper is to provide a global assessment of the exotic mammals of Argentina, their pathways, impacts, and a synthesis of their attributes as potential invasive species. We reviewed and compiled data from a diversity of sources and databases on alien mammals occurring in feral state exclusively. We recorded 18 species of exotic mammals for Argentina. The majority of introductions occurred between the 18th and 19th centuries and their ports of entry were located in temperate ecosystems, between 34° and 55° SL. Most of their entry pathways were associated with human activities (e.g. sport hunting, food and fur industry). The exotic mammals occupy ecoregions similar to their original distributions, but most of them have experienced a range expansion to novel habitats. The fauna of exotic mammals of Argentina represents a good opportunity to understand the dynamics of the invasion process as they represent a diversity of ecological groups and environmental contexts.

Elevation patterns in rodent diversity in the dry Andes: disentangling the role of environmental factors

Abstract Biodiversity patterns are the result of the interaction of numerous contemporary factors and historical opportunities for allopatric speciation. Several hypotheses regarding climatic features and topographic characteristics have been reported as determinants of species richness along elevation gradients. However, how these factors interact to shape small mammal species richness along the dry Andes ecosystem is not well understood. The objectives of this paper were to analyze patterns of species diversity along the central dry Andes, and to evaluate how climatic and topographic factors explain diversity patterns. Our results showed a positive and monotonic relationship between small mammal species richness and altitude, whereas abundance patterns showed a midelevation peak. Climate and topography were the most important predictor variables explaining small mammal species richness and abundance patterns in the Andes. This study underlines the role of the Andes in promoting and sustaining biodiversity, as well as the need to encourage conservation planning in mountain ecosystems. Resumen Los patrones de biodiversidad son el resultado de la interacción entre numerosos factores contemporáneos y eventos históricos que propician la especiación alopátrica. Numerosos factores climáticos y topográficos han sido mencionados como determinantes para los patrones altitudinales de riqueza de especies. Sin embargo es poco conocido aún como estos factores interactúan para modelar la riqueza de especies a lo largo de la Cordillera de los Andes. Los objetivos de este trabajo fueron analizar los patrones de diversidad de especies a lo largo de los Andes templados, y evaluar como los factores climáticos y topográficos explican los patrones de riqueza y abundancia de especies. Nuestros resultados muestran una relación monotónica y positiva entre riqueza de especies y altura. Mientras el patrón de abundancia es unimodal. Para ambos patrones el clima y la topografía son las variables predictoras más importantes. Este estudio resalta el rol de los Andes en promover y sostener la biodiversidad, y acentúa la necesidad de fomentar planes de conservación en ecosistemas montanos.

Vigilance behaviour of the year-round territorial vicuña (Vicugna vicugna) outside the breeding season: Influence of group size, social factors and distance to a water source

We conducted focal observations of vicuña, a year-around territorial mammal, to compare vigilance behaviour between territorial and bachelor males outside the reproductive season. We hypothesized that the time spent vigilant would depend on male social status, considering the potential effects of several variables: sampling year, group size, distances to the nearest neighbour and to a vega (mountain wetland). We fit GLM models to assess how these variables, and their interactions, affected time allocation of territorial and bachelor males. We found non significant differences between territorial and bachelor males in the time devoted to vigilance behaviour. Vigilance of territorial males was influenced by the sampling year and the distance to the vega. In turn, vigilance in bachelor males was influenced mainly by the sampling year, the group size and the distance to the vega. Our results suggest that sampling year and distance to the vega are more important than social factors in conditioning the behaviour of male vicuñas, during the non-reproductive season. Future studies of behaviour in water-dependant ungulates, should consider the influence of water and forage availabilities, and the interactions between group size and other variables.

Do cortisol and corticosterone play the same role in coping with stressors? Measuring glucocorticoid serum in free‐ranging guanacos (Lama guanicoe)

Habitat can constrain and shape successful ecological and physiological strategies, thus providing the context for the evolution of life-history traits. However, unpredictable challenges, such as storms, natural disasters, and human activities can also have great effects on stress. Glucocorticoids (GCs) are adrenal steroid hormones that play an important role in how vertebrates cope with these predictable and unpredictable environmental challenges. Although assessing GCs levels can have many applications in the study of wildlife and/or captive animals, with or without capturing individuals, it requires a species-specific complete validation (analytical and biological) before its use. In this work, our aim was to: (a) validate a radioimmunoassay (RIA) for measuring GCs levels in L. guanicoe serum; (b) assess cortisol and corticosterone levels (if present) in serum of wild L. guanicoe individuals; and (c) compare the response to acute stressors (handling, shearing, and release). Our results successfully: (a) validated RIA for asses GCs levels in wild ungulates; (b) confirmed the presence for cortisol and corticosterone and showed that both GCs are differently affected by environmental stimuli in L. guanicoe; and (c) showed that GCs exhibit different patterns in the field and in response to acute stressors, making these camelids an interesting endocrinological model when seeking the adaptive functions of a given variation and further emphasizing the complexity of GC physiology in wild mammals.

Do Cortisol and Corticosterone have the same role to cope with stressors? Measuring Serum Glucocorticoid in free-ranging Guanacos (Lama guanicoe)

Habitat can constrain and shape successful ecological and physiological strategies, thus providing the context for the evolution of life-history traits. However, unpredictable challenges, such as storms, natural disasters, and human activities can also have great effects on stress. Glucocorticoids (GCs) are adrenal steroid hormones that play an important role in how vertebrates cope with these predictable and unpredictable environmental challenges. Although assessing GCs levels can have many applications in the study of wildlife and/or captive animals, with or without capturing individuals, it requires a species-specific complete validation (analytical and biological) before its use. In this work, our aim was to: (a) validate a radioimmunoassay (RIA) for measuring GCs levels in L. guanicoe serum; (b) assess cortisol and corticosterone levels (if present) in serum of wild L. guanicoe individuals; and (c) compare the response to acute stressors (handling, shearing, and release). Our results successfully: (a) validated RIA for asses GCs levels in wild ungulates; (b) confirmed the presence for cortisol and corticosterone and showed that both GCs are differently affected by environmental stimuli in L. guanicoe; and (c) showed that GCs exhibit different patterns in the field and in response to acute stressors, making these camelids an interesting endocrinological model when seeking the adaptive functions of a given variation and further emphasizing the complexity of GC physiology in wild mammals.

Habitat selection and coexistence in small mammals of the southern Andean foothills (Argentina)

Habitat partitioning is considered one of the main mechanisms of coexistence among small mammals. This is especially evident in arid environments where resources are particularly scarce. Habitat characteristics such as vegetation heterogeneity and complexity are expected to increase species coexistence, increasing the number of microhabitats that can be occupied by species with different requirements. The Andean foothills can be considered as an ecotone between the Monte and Altoandina phytogeographic provinces as they harbor species from both. Consequently more species are thought to coexist in this area. The objectives of this study were to assess the macro- and microhabitat selection of the small mammal assemblage inhabiting the Andean foothills during wet and dry season and to determine how animals segregate environmental resources to ensure their coexistence. We found that habitat selection occurs at both scales in the Andean foothills. Two species, Eligmodontia moreni and Phyllotis xanthophygus, were capable of distinguishing among macrohabitat types, whereas all species showed habitat selection at the microhabitat scale. We registered selection during both seasons, with some overlap of resource selection during the wet season and the greatest segregation of microhabitat resources during the dry season. Therefore, this work evidence that the assembly of small mammals is sensitive to habitat structure especially in dry seasons where resources are constraints due to arid conditions of Andean foothills.