Keyword: abundance

Bat community structure in urban green areas of northeastern Brazil

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The structure of the habitat can influence the bat community, limiting the species to use certain environments. Considering the more tolerant species, these can be found in forest fragments surrounded by urban matrix or heavily wooded places. This study aimed to characterize the bat community in the urban green areas of Greater Aracaju, Sergipe. The campaigns were conducted during two consecutive monthly nights in each area. Bats were captured using 10 mist nets. The abundance, richness, diversity, and composition of bats were characterized for each area. In addition, the models of abundance and sufficiency of the sampling effort were evaluated. We captured 599 individuals, representing 13 species in three families, with an effort of 77.760 m²/h. Secretaria de Estado da Fazenda de Sergipe had the highest value of the diversity index (H’ = 1.78), followed by Universidade Federal de Sergipe (H’ = 1.62) and Vila Militar dos Officiais do Exército (H’ = 1.55), with a difference observed only between the SEFAZ and Vila areas. The observed richness was lower than expected in all areas. Only the UFS and SEFAZ differed in species composition. For urban green areas in the state, Artibeus planirostris and Myotis riparius correspond to the new records. The observed difference in diversity between the SEFAZ and Vila may be associated with the greater evenness of the SEFAZ and the dominance of Artibeus lituratus in Vila. This study provides relevant information on the subject, highlighting the need to obtain a better understanding of this group in urban green environments.

Estrutura da comunidade de morcego em áreas verdes urbanas do nordeste do Brasil. A estrutura do habitat pode influenciar a comunidade de morcegos, limitando a espécie a utilizar determinados ambientes. Considerando as espécies mais tolerantes, estas podem ser encontradas em fragmentos florestais circundados por matriz urbana ou locais fortemente arborizados. Este estudo teve como objetivo caracterizar a comunidade de morcegos nas áreas verdes urbanas da Grande Aracaju, Sergipe. As campanhas foram realizadas durante duas noites mensais consecutivas em cada área. Os morcegos foram capturados com 10 redes de neblina. Para cada área, foram caracterizadas a abundância, riqueza, diversidade e composição de morcegos. Além disso, foram avaliados os modelos de abundância e suficiência do esforço amostral. Foram capturados 599 indivíduos, representando 13 espécies de três famílias, com um esforço de 77,760 m².h. A Secretaria de Estado da Fazenda de Sergipe apresentou o maior índice de diversidade (H’ = 1,78), seguida pela Universidade Federal de Sergipe (H’ = 1,62) e Vila Militar dos Oficiais do Exército (H’ = 1,55), com diferença observada apenas entre as áreas SEFAZ e Vila. A riqueza observada foi menor que a esperada em todas as áreas. Apenas a UFS e a SEFAZ diferiram na composição de espécies. Para as áreas verdes urbanas do estado, Artibeus planirostris e Myotis riparius correspondem aos novos registros. A diferença de diversidade observada entre a SEFAZ e a Vila pode estar associada à maior equitabilidade da SEFAZ e à predominância de Artibeus lituratus na Vila. Este estudo fornece informações relevantes sobre o assunto, destacando a necessidade de se obter um melhor conhecimento desse grupo em ambientes verdes urbanos.

Graphical abstract for the article “Bat community structure in urban green areas of northeastern Brazil” (Santos Bezerra & Bocchiglieri, 2024)

Decrease in the occurrence of the South American fur seal (Arctocephalus australis) in San Matías Gulf after a sudden episode of reoccupation

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The colonies of South American fur seals, Arctocephalus australis (SAFS), are currently experiencing population recovery, and as a consequence many coastal areas have been reoccupied. These areas are often haul-out sites used by SAFS for resting during the post-reproductive (winterly) season, and may be playing a key role in the population recovery process since they seem to be located close to winter feeding areas that are far from the breeding colonies. This study reports on the trend in abundance of SAFS in a recently reoccupied winter area, the San Matías Gulf (SMG). The trend was evaluated with generalized linear models between 2007 and 2017 in two sectors of the SMG, Islote Lobos, the only rookery of this species in the area, and the northwest marine area of the gulf. Both sectors showed a negative trend. For Islote Lobos, the best selected models estimated a mean annual rate between -12.2% and -17.6%, and for the northwest area, between -19.02% and -29.9%. The population context suggests that most SAFS observed in 2007 may have been selecting other habitats over the following years; however, simultaneous censuses throughout their distribution range are needed in order to understand the redistribution and recolonization processes.

Disminución en la ocurrencia del lobo marino sudamericano Arctocephalus australis en el Golfo San Matías después de un episodio repentino de reocupación. Las colonias del lobo marino de dos pelos sudamericano, Arctocephalus australis (SAFS), están experimentando una recuperación poblacional y como consecuencia muchas áreas costeras han sido reocupadas nuevamente. Muchas de estas áreas son apostaderos utilizados por los SAFS para descansar durante la temporada post-reproductiva (invernal). Las mismas pueden estar jugando un papel clave en el proceso de recuperación ya que estarían ubicadas cerca de áreas de alimentación invernales que se encuentran distantes de las colonias reproductivas. El presente estudio reporta la tendencia en la abundancia de SAFS en un área invernal recientemente ocupada, el Golfo San Matías (GSM). La tendencia se evaluó con modelos lineales generalizados entre los años 2007 y 2017 para dos sectores del golfo: el Islote Lobos, el único apostadero de esta especie, y el área marina del noroeste del golfo. Ambos sectores mostraron una tendencia negativa. Para el Islote Lobos, los modelos seleccionados estimaron una tasa promedio anual entre -12.2% y -17.6%, y para el área marina noroeste entre -19.02% y -29.9%. El contexto a nivel poblacional sugiere que la mayoría de los SAFS observados en 2007 pueden haber seleccionado otros hábitats durante los siguientes años. Sin embargo, para comprender los procesos de redistribución y recolonización se necesitan censos simultáneos en todo su rango de distribución.

Influence of bat morphology on structural properties of a plant-frugivore network

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Identifying factors that influence the importance of species for mutualistic interactions is crucial for designing management and conservation strategies that aim to conserve ecosystem functions. Even though bats are key seed-dispersers, factors that influence their importance for structural properties of seed-dispersal networks are poorly studied. We evaluated the influence of cranial morphology, phylogenetic legacy and abundance of frugivorous bats on the structural properties of an interaction network in a tropical dry forest. Consequently, we captured bats and identified interactions with plants by collecting and identifying seeds from fecal samples. Then, we described network structure by using network-level indexes and assessed the contribution of bats to network structure by using species-level indexes. Analysis of the mutualistic network indicated that: (1) there are few species with high number of interactions, (2) the structure was more compartmentalized and less nested than expected, (3) there are subgroups of bats and plants that are highly connected among them, and (4) network would collapse promptly with the loss of bats with most interactions (generalist). Furthermore, bats that contribute the most to network structure tended to have short rostrum and wide cranium and/or were abundant, with Artibeus lituratus being the most important bat; however, contribution to network structure did not have phylogenetic signal. According to the interaction neutrality hypothesis, species’ abundances drive the chances of individuals encountering and interacting with other species. However, our results suggest that frugivore bats are not functionally equivalent since contribution of species to network’s structure was associated with both cranial morphology and abundance.

Influencia de la morfología de los murciélagos en las propiedades estructurales de una red de frugívoros y plantas. La identificación de los factores que influencian la importancia de las especies para las interacciones mutualistas es crucial para diseñar estrategias de conservación y manejo destinadas a conservar la funcionalidad de los ecosistemas. A pesar de que los murciélagos son dispersores claves de semillas, los factores que influencian la importancia de estos para las propiedades estructurales de las redes de dispersión de semillas han sido poco estudiados. Evaluamos la influencia de la morfología craneal, el legado filogenético y la abundancia de murciélagos frugívoros sobre las propiedades estructurales de una red de interacción en un bosque seco tropical. Para esto, capturamos murciélagos e identificamos interacciones con plantas a través de las semillas colectadas en sus heces. Luego describimos la estructura de la red utilizando índices a nivel de red y evaluamos la contribución de murciélagos a la estructura de la red utilizando índices a nivel de especie. El análisis de la estructura de la red mutualista entre murciélagos frugívoros y planas indicó que: (1) hay pocas especies con alto número de interacciones, (2) la estructura fue más compartimentalizada y menos anidada de lo esperado, (3) hay subgrupos de murciélagos y plantas que están altamente conectadas entre ellas y (4) la red podría colapsar rápidamente debido a la pérdida de murciélagos con muchas interacciones (generalistas). Los murciélagos que más contribuyen a la estructura de la red tienden a presentar rostro corto y cráneo ancho y/o a ser abundantes, siendo Artibeus lituratus el murciélago con mayor importancia para la estructura de la red; sin embargo, la contribución a la estructura de la red no presentó señal filogenética. Según la hipótesis de neutralidad en interacciones mutualistas, la abundancia determina las posibilidades de que los individuos se encuentren e interactúen con otras especies. Sin embargo, nuestros resultados sugieren que los murciélagos frugívoros no son funcionalmente equivalentes para la estructura de la red, dado que la contribución de estos a la estructura de la red estuvo asociada tanto con la morfología craneal como con su abundancia.

Parámetros poblacionales de Oligoryzomys longicaudatus en Cholila (Chubut, Argentina)

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El objetivo de este estudio fue describir y cuantificar parámetros poblacionales de Oligoryzomys longicaudatus en Cholila (Chubut, Argentina). Para el muestreo se utilizaron líneas de remoción ubicadas estacionalmente durante cinco años en hábitats de bosques y arbustales. Además se usaron tres grillas de captura, marcado y recaptura en hábitats de arbustal, de manera bimensual durante tres años. Se estimó abundancia para cada hábitat y estación. Los animales fueron clasificados reproductivamente como activos o inactivos, realizándose conteo de embriones en hembras capturadas muertas y se estableció prevalencia de preñez en ambos hábitats. La edad de los individuos se estimó en base a la masa corporal. Se estableció tasa de sobrevida y condición de animales residentes o transeúntes para los individuos capturados en grillas. O. longicaudatus presentó fluctuaciones estacionales y diferencias interanuales entre hábitats en los valores de abundancia, siendo máximas en otoño-invierno en el arbustal y en verano-otoño en el bosque. Los adultos estuvieron más representados en todo el periodo de estudio, seguido por subadultos y bajos porcentajes de juveniles. La actividad reproductiva presentó diferencias estacionales e interanuales y entre hábitats. El número de transeúntes fue superior al de residentes, especialmente para machos. La sobrevida fue mayor en otoños e inviernos. Las diferencias de los valores de abundancia entre los años podrían ser explicadas por los parámetros reproductivos y la estructura de la población.

Population parameters of Oligoryzomys longicaudatus in Cholila (Chubut, Argentina). The objective of this study was to describe and quantify population parameters of O. longicaudatus in Cholila (Chubut, Argentina). Individuals were sampled seasonally over 5 years by removal trapping in forest and shrubland habitats, and bimonthly over 3 years with capture-mark-recapture trapping in 3 grids located in shrubland habitats. Abundance was estimated for each habitat and season. Animals were classified as reproductively active or inactive, the number of embryos in females captured dead was tallied, and the frequency of pregnancy was recorded for both habitats. Ages of individuals were estimated from body mass. Survival rate and residency status (resident vs. transient) were determined for individuals from live-trap grids. O. longicaudatus showed seasonal fluctuations and inter-annual differences in abundances between habitats; abundances were greatest in autumn-winter in shrubland and in summer-autumn in forest. Adults dominated the population throughout the study period, followed by sub-adults and juveniles in low percentages. Reproductive activity exhibited seasonal and inter-annual differences as well as differences between habitats. The number of transients was higher than residents, especially for males. Survival was higher in autumn and winter than in spring and summer. Differences in abundance among years can be explained by reproductive parameters and population structure.

Assemblage of chiropterans in a remnant of Semideciduous Seasonal Forest in southern Brazil and latitudinal patterns of species diversity in the Atlantic Forest

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Observed and expected richness, capture success, diversity, dominance, evenness and the effect of latitude on the above variables at the regional level were evaluated with regard to the chiropteran fauna of a semideciduous seasonal forest remnant in the state of Rio Grande do Sul, southern Brazil. Sampling occurred between July 2008 and June 2010 using mist nets erected at ground level. So that chiropteran fauna could be described and compared to other studies in the Atlantic Rainforest throughout the 10°–30° S using multivariate regression. One hundred and sixteen specimens were captured, comprising 9 species and 3 families: Phyllostomidae, Vespertilionidae and Molossidae. Capture success was 0.0008 ind/m²h, with a diversity index (H’) of 1.623; dominance (BP) of 0.4783; evenness (J’) of 0.7385, and expected richness of 11 species. Sturnira lilium had the highest capture rate. There was a significant relationship between latitude and capture success and richness (CS: R² = 0.64, p = 0.0005; S: R² = 0.28, p = 0.0473). Distribution and abundance of bats at the regional scale was related to latitude as well as the differentiation of assemblages in the Atlantic Rainforest.

Assembleia de quirópteros de um remanescente de Floresta Estacional Semidecidual do sul do Brasil e gradientes latitudinais na diversidade de espécies. A riqueza observada e esperada, o sucesso de captura, a diversidade, a dominância e a equitabilidade (evenness), bem como a influência da latitude sobre estas variáveis em escala regional, foram avaliados, considerando-se a quiropterofauna de um remanescente de Floresta Estacional Semidecidual no estado do Rio Grande do Sul, Brasil. As amostragens transcorreram de julho de 2008 a junho de 2010 por meio de oito redes de neblina instaladas ao nível do solo. Assim, foi possível descrever a quiropterofauna e compará-la, usando-se regressão multivariada, com outros estudos realizados na Mata Atlântica ao longo de um gradiente de 10° a 30° S. Capturaram-se 116 indivíduos pertencentes a nove espécies e três famílias, Phyllostomidae, Vespertilionidae e Molossidae. O sucesso de captura foi 0.0008 ind/m²h. O índice de diversidade (H’) foi 1.623, dominância (BP), 0.4783, evenness (J’), 0.7385, e a riqueza esperada compreendeu 11 espécies. Sturnira lilium registrou o maior número de capturas. Encontrou-se relação significativa entre latitude e sucesso de captura e riqueza (SC: R² = 0.64, p = 0.0005; S: R² = 0.28, p = 0.0473). A distribuição e a abundância de morcegos, em escala regional, estão relacionadas com a latitude, assim como a diferenciação das assembleias na Mata Atlântica.

Estrutura de comunidade de morcegos em relictos de Floresta Estacional Decidual no sul do Brasil

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Por ser um grupo extremamente especioso, abundante e ocupar os mais variados habitats e recursos, os morcegos têm sido considerados excelentes modelos para estudos sobre diversidade. O presente estudo teve como objetivo descrever a estrutura da comunidade de morcegos em três áreas sob os domínios da Floresta Estacional Decidual, no município de Frederico Westphalen, no extremo norte do estado do Rio Grande do Sul. De outubro de 2005 a setembro de 2006, cada área recebeu esforço amostral de uma noite por mês do pôr ao nascer do sol. Em 36 noites de trabalho foram obtidas um total de 511 capturas de morcegos de 15 espécies e três famílias. Vespertilionidae apresentou sete espécies, seguida de Phyllostomidae com seis e Molossidae com duas espécies. O teste não paramétrico de Kruskal-Wallis revelou não haver diferenças significativas entre as três áreas. Sturnira lilium (É. Geoffroy, 1810) e Artibeus lituratus (Olfers, 1818) foram as espécies mais capturadas, com 52.4% e 34.4% de abundância relativa, respectivamente. As espécies frugívoras representaram 90.5% do total de capturas, seguidos pelos insetívoros com 9.3% e carnívoros com apenas 2%. Não houve diferenças significativas na composição da comunidade entre os meses e nem entre as estações do ano, sugerindo ausência de variações sazonais. As curvas de acumulação e de rarefação de espécies indicam que com a continuidade dos esforços o número de espécies continuaria aumentando. A ocorrência de espécies consideradas raras no sul do Brasil reforça a importância dos fragmentos florestais para a manutenção da diversidade da fauna de morcegos.

Bat community structure in a Seasonal Deciduous Forest fragment in southern Brazil. Because of their being extremely specious, abundant and occupying the most diverse habitats and food resources, bats have been considered excellent models for diversity studies. This study aimed to describe the bat community structure in three sites in the Seasonal Deciduous Forest of the city of Frederico Westphalen, in northern Rio Grande do Sul state. From October 2005 to September 2006, each of the three sites received a monthly sampling effort of one night from dusk to dawn. In 36 nights of field work were obtained a total of 511 catches of 15 species of bats and three families. Vespertilionidae presented seven species, followed by six Phyllostomidae and Molossidae with two species. The nonparametric Kruskal-Wallis test revealed no significant differences between sites. Sturnira lilium and Artibeus lituratus were the main species caught, with 52.4% and 34.4% relative abundance, respectively. Frugivorous species accounted for 90.5% of the total catch, followed by insectivores with 9.3% and carnivores with only 2%. There were no significant differences in community composition between months and even between the seasons, suggesting the absence of seasonal variations. The curves of accumulation and rarefaction of species indicate that with the continuing efforts the number of species continue to grow. The occurrence of species considered rare in southern Brazil reinforces the importance of forest fragments to maintain the diversity of the bat faunas.

Uso de refugios por tres especies de murciélagos filostómidos (Chiroptera: Phyllostomidae) en el Área Natural Única Los Estoraques, Norte de Santander, Colombia

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La ecología del refugio es importante en la evolución de los murciélagos y su biología. Describimos el uso de refugios en un bosque seco en el nororiente de Colombia. Se determinó la relación entre variables ambientales en refugios (temperatura, humedad relativa, velocidad del viento, luz, altura de percha, altura máxima del refugio y altitud) y abundancia relativa de Artibeus jamaicensis, Carollia brevicauda y Anoura geoffroyi en la época seca y lluviosa. Se determinaron diferencias entre variables ambientales de refugios con un análisis de varianza y Kruskal-Wallis. Se determinó la relación entre variables ambientales y abundancia con un análisis de correspondencia canónica (ACC). Se encontraron ocho refugios naturales y tres artificiales. Para la variable luz, se encontraron diferencias entre los refugios. La altura máxima del refugio también mostró diferencias, así como la altura de percha. Velocidad del viento, humedad relativa y temperatura no variaron entre refugios. Con el ACC se determinaron asociaciones entre A. jamaicensis y humedad relativa, velocidad del viento, luz, altura de percha y altura máxima del refugio. Para C. brevicauda la asociación fue con temperatura y para A. geoffroyi fue con altitud. Se encontraron diferencias en la abundancia de A. jamaicensis en seis de los siete refugios entre épocas. C. brevicauda y A. geoffroyi no mostraron diferencias en la abundancia entre épocas.

Roost use by bats (Chiroptera: Phyllostomidae) in the Natural Area Los Estoraques, Norte de Santander, Colombia. Roost ecology is important for bats evolution and biology. We described roost use in a dry forest of north eastern Colombia. Relations between roost environmental variables (temperature, relative humidity, wind speed, light, perch height, maximum height of roost and altitude) and relative abundance of Artibeus jamaicensis, Carollia brevicauda and Anoura geoffroyi during dry and rainy seasons were determined. Differences between environmental variables of roosts using variance analysis and Kruskal-Wallis tests were determined. The relation between environmental variables and abundance was assessed with a canonical correspondence analysis (CCA). Eight natural and three artificial roosts were found. Regarding environmental variables, light, maximum height of roost and perch height showed significant differences among roosts, while wind speed, relative humidity and temperature presented no variation. Associations between A. jamaicensis and relative humidity, wind speed, light, perch height and maximum height of roost were found through CCA. For C. brevicauda and A. geoffroyi, an association with temperature and altitude, respectively, was found. Abundance of A. jamaicensis varied in six of seven roosts between seasons, while C. brevicauda and A. geoffroyi showed no seasonal differences.

Densidad, estructura social, actividad y manejo de guanacos silvestres (Lama guanicoe) en el sur del Neuquén, Argentina

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Los guanacos (Lama guanicoe) son los ungulados silvestres más abundantes y ampliamente distribuidos de Sudamérica, aunque su abundancia y rango de distribución disminuyó drásticamente en el último siglo. En Patagonia, la esquila en vivo de guanacos silvestres es promovida por organismos gubernamentales como una actividad complementaria a la ganadería que contribuiría a conservar sus poblaciones. La falta de estudios ecológicos sobre poblaciones que habitan campos privados dificulta la evaluación de posibles efectos negativos de esta actividad. Nuestro objetivo fue estimar la densidad, la estructura social y las actividades de una población de guanacos silvestres en un establecimiento ganadero y evaluar los efectos de un evento de manejo. Estimamos la densidad y la estructura social, dentro y fuera del área manejada, y analizamos las actividades individuales antes y después del manejo, entre invierno 2004 y verano 2005. La densidad fue similar en ambas épocas y el tamaño de grupos de machos decreció en primavera. Los grupos familiares fueron la estructura social más frecuente. La alimentación fue la actividad más común en ambas estaciones. La actividad «reposo» en verano se asoció positivamente con la temperatura. Nuestros resultados sobre efectos del manejo son limitados debido al bajo éxito de captura y que pocos ejemplares fueron esquilados; sin embargo, sugieren que la esquila no modificó la estructura social de la población manejada en el corto tiempo. La continuidad de estos estudios es esencial para evaluar la sustentabilidad de esta actividad y su valor potencial como herramienta de conservación de la especie.

Density, social structure, activity and management of wild guanacos (Lama guanicoe) in southern Neuquén Province, Argentina. Guanacos (Lama guanicoe) are the most abundant and widespread wild South American ungulate though both their abundance and range distribution have drastically decreased in the last century. In Patagonia, live-shearing of wild guanacos is being promoted by wildlife agencies as a complementary activity for sheep farmers that may help to conserve populations of guanacos. The lack of ecological studies of guanaco populations inhabiting private ranches hinders the evaluation of possible negative effects of live-shearing. Our objective was to estimate the density, social structure and activities on a free-ranging guanaco population within a livestock ranch and to assess the effect of a shearing event. We estimated population density and social structure, inside and outside of an area being managed and analysed individual behaviour, before and after shearing, between winter 2004 and summer 2005. Density was similar in both seasons and male group size decreased in spring. Family groups were the most frequent social structure. Foraging was the most common activity in both seasons. Resting activity in summer was positively associated with temperature. Our results on the effects of management are limited because capture success was low and few guanacos were sheared; however, our results suggest that live-shearing did not modify the social structure of the managed population in the short-term. The continuity of these studies is essential for a long-term evaluation of sustainability of this activity and its potential value as a conservation tool for the species.

Caracterización de la comunidad de mamíferos no voladores en las estribaciones orientales de la Cordillera del Kutukú, Amazonía ecuatoriana

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Las estribaciones orientales de los Andes ecuatorianos están consideradas entre los «puntos calientes» en términos de biodiversidad. A pesar de que la región contiene un elevado número de especies de mamíferos, pocos estudios mastozoológicos se han llevado a cabo hasta ahora. Este manuscrito presenta los resultados de un muestreo intensivo de 11 meses de duración (noviembre, 2001 – septiembre, 2002) de los mamíferos medianos y grandes en la cuenca alta del río Mangosiza, en las estribaciones orientales de la cordillera del Kutukú, Amazonía suroriental ecuatoriana. Utilizando transectos en línea, registros indirectos de huellas y signos, trampas fotográficas y entrevistas a pobladores locales, registramos un total de 47 especies de mamíferos (incluyendo 2 marsupiales, 9 desdentados, 8 primates, 16 carnívoros, 4 ungulados, 7 roedores y 1 lagomorfo).

Non-volant mammal community characterization on the eastern slopes of Kutukú mountain range, Ecuadorian Amazon. The eastern slopes of the Andes in Ecuador are considered among the global biodiversity “hotspots”. Although the region harbors a rich mammal fauna, few surveys of non-volant mammals have been conducted. This paper presents the results of an intensive survey of 11 months (November 2001 – September 2002) of the medium to large non-volant mammals in the upper Mangosiza River Basin, eastern slopes of the Kutukú mountain range, southeastern Ecuadorian Amazon. Using line transects, indirect records of tracks and signs, camera trapping, and interviews to local people, we recorded a total of 47 species of mammals (including 2 marsupials, 9 xenarthrans, 8 primates, 16 carnivores, 4 ungulates, 7 rodents, and 1 lagomorph).

Evaluation of a fecal-pellet index of abundance for mountain vizcachas (Lagidium viscacia) in Patagonia

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We present an index of abundance based on fecal-pellet counts for mountain vizcachas (Lagidium viscacia) in the Patagonian steppe. We use regression to calibrate the index to size of populations of mountain vizcachas estimated by captures and intensive observations at seven sites. By obtaining index values on two different occasions and comparing the regressions for these two occasions, we determine that this is a valid constant-proportion index under the conditions of our study. The use of this index should be limited to populations of mountain vizcachas inhabiting low, vertical cliffs. Its use outside the study area requires the assumption that local conditions do not affect the relationship between the number of piles of pellets and the number of mountain vizcachas which we found in our study area. We advise that a validation study be done locally wherever the index is to be used. If this is not possible, the index should be used to compare relative rather than absolute abundance, and results should be interpreted with caution.

Evaluación de un índice de abundancia para el chinchillón en la Patagonia. Presentamos un índice de abundancia para chinchillones (Lagidium viscacia) en la estepa patagónica basado en conteos de pilas de fecas. Usamos regresión para calibrar el índice con los tamaños de poblaciones de chinchillones estimados con capturas y observaciones intensivas en siete sitios. Al obtener valores del índice en dos ocasiones distintas y comparar las regresiones para esas dos ocasiones, determinamos que el índice es válido como un índice de proporciones constantes en las condiciones de nuestro estudio. El uso de este índice debería limitarse a poblaciones de chinchillones que habiten acantilados bajos y verticales. Su uso fuera del área de estudio requiere suponer que las condiciones locales no afectan la relación entre el número de pilas de fecas y el número de chinchillones que encontramos en nuestra área de estudio. Aconsejamos que se haga una validación local siempre que se vaya a usar este índice. Si esto no es posible, el índice debería usarse para comparar densidades relativas en vez de absolutas y debería tenerse precaución al analizar los resultados.