Abundance of Conepatus Chinga (Carnivora, Mephitidae) and Other
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Abundance of Conepatus chinga (Carnivora, Mephitidae) and other... 303 Abundance of Conepatus chinga (Carnivora, Mephitidae) and other medium-sized mammals in grasslands of southern Brazil Carlos B. Kasper1, Vinícius A. G. Bastazini2, José B. G. Soares3 & Thales R. O. de Freitas4 1. Programa de Pós-Graduação em Biologia Animal, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, 90510-970 Porto Alegre, RS, Brasil. ([email protected]) 2. Programa de Pós-Graduação em Ecologia, Laboratório de Ecologia Quantitativa, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Prédio 43411, sala 205, 90510-970 Porto Alegre, RS, Brasil. ([email protected]) 3. Instituto Pró-Pampa, Nossa Senhora das Graças 294, 96330-000 Arroio Grande, RS, Brasil. ([email protected]) 4. Laboratório de Citogenética e Evolução, Departamento de Genética, Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves, 9500, Prédio 43323, sala 101, 90510-970 Porto Alegre, RS, Brasil. ([email protected]) ABSTRACT. Between January 2007 and December 2010, the abundance of medium-sized mammals was studied, with special focus on the Molina’s hog-nosed skunk, Conepatus chinga (Molina, 1782), at four locations in southern Brazil. In this study, transect line methodology was used to obtain data for Distance Analyses. Transects were traveled by car at night, searching with spotlights along the edges of secondary roads in agricultural landscapes. Along 1,811 km, we obtained 620 observations of 20 mammal species. The most common species was the exotic European hare, Lepus europaeus (Pallas, 1778); the highest abundance estimated for South America was observed in one of the study areas, where its density was estimated as 32 individuals/km². Carnivores were the most commonly recorded mammals, represented by 10 species and comprising 51% of all observations. Molina’s hog-nosed skunk occurred in all study areas, but occurred in sufficient numbers to obtain density estimates in only two of the areas. We estimated 1.4 to 3.8 individuals/km², in the first density estimate made by the transect method for a member of Conepatus in the Neotropics. These values are similar to those estimated for North American species of Mephitidae. In Brazil, C. chinga is apparently more abundant in the Pampa biome than in the grasslands of the Atlantic Forest. For two other carnivores, Lycalopex gymnocercus (Fisher, 1814) and Cerdocyon thous (Linnaeus, 1766), we estimated preliminary densities that were similar to those previously cited for different regions. KEYWORDS. Density, Pampa, transect lines, sympatric species. RESUMO. Abundância de Conepatus chinga (Carnivora, Mephitidae) e outros mamíferos de médio porte nos campo do sul do Brasil. Entre janeiro de 2007 e dezembro de 2010 a abundância de mamíferos de médio porte foi estudada, com especial ênfase no zorrilho Conepatus chinga (Molina, 1782) em quatro locais no sul do Brasil. Neste estudo, foi utilizada a metodologia de transectos lineares de forma a obter dados para análises de densidade com uso do software Distance. Os transectos foram percorridos de carro, à noite, procurando por animais na periferia de estradas secundárias, com o uso de holofotes de longo alcance. Em 1.811 km percorridos, foram obtidos 620 registros de 20 espécies de mamíferos. A espécie mais comum foi a lebre européia Lepus europaeus (Pallas, 1778), para a qual, em uma das áreas estudadas, foi obtida a maior estimativa de abundância já registrada para a América do Sul, com uma densidade estimada de 32 indivíduos por km². Carnivora foi a ordem mais comumente registrada, representada por 10 espécies que, juntas, compreenderam 51% de todas as visualizações. O zorrilho ocorreu em todas as áreas estudadas, embora só tenha sido registrado em número suficiente para a obtenção de estimativas de densidade em duas destas áreas. A densidade do zorrilho foi estimada em 1,4 a 3,8 indivíduos por km², sendo esta a primeira estimativa por transectos lineares do gênero Conepatus na região Neotropical. Estes valores são similares aos observados para mefitídeos norte-americanos. No Brasil, C. chinga é aparentemente mais abundante no Pampa do que nos campos de altitude da Mata Atlântica. Para outras duas espécies, Lycalopex gymnocercus (Fisher, 1814) e Cerdocyon thous (Linnaeus, 1766), foram feitas estimativas preliminares de densidade que apontaram valores semelhantes aos de outras regiões de ocorrência das espécies. PALAVRAS-CHAVE. Densidade, Pampa, transecções lineares, espécies simpátricas. Species abundance is a central aspect in of fragmentation on mammal assemblages in the Atlantic population ecology. Abundance can be affected by Forest. Yet, in general, there is a lack of knowledge of several ecological factors, including food availability, this aspect for most Neotropical mammals, even for the competition and predation. Two basic and different most common species. measures of abundance can be estimated by sampling The Neotropical mammal fauna is mostly animal populations: density and abundance. Absolute composed of small species, such as rodents, marsupials density refers to a quantitative measure of numbers and bats. Among medium-sized mammals (> 1 kg), of individuals per area, which can be converted into most of the species are arboreal (e.g., primates), which an estimate of population size. Abundance refers to together with small mammals represent nearly 88% of population densities relative to a unit other than area, all mammal diversity in South America (FONSECA et al., such as records per hour surveyed or observations 1999). However, the Neotropical region has extensive per kilometer sampled (CASSEY, 1999). Indices are areas of open habitat, often resembling the landscape of generally based on the assumption that the sample African savannas. In contrast to African mammals, the represents a constant but unknown proportion of the majority of South American mammals are inconspicuous, population. These indices are easily obtained and useful with a relatively small number of medium- to large- for comparing different sites or trends with repeated sized species. Most of them have secretive habits and sampling over time (GESE, 2001). CHIARELLO (1999), for are difficult to observe. example, used abundance indices to evaluate the impact Even relatively common species have been poorly Iheringia, Série Zoologia, Porto Alegre, 102(3):303-310, 30 de setembro de 2012 09_XX-XX_ISZ-111_Kasper et al.indd 303 11/10/2012 17:07:37 304 KASPER et al. studied, and abundance estimates are few, especially based Rio Grande do Sul in the municipality of Arroio Grande on transect lines. In Brazil, this method has been used (33°19’S, 53°54’W), near the border with Uruguay, was in aerial counts of marsh deer Blastocerus dichotomus studied between February 2008 and April 2009. The (Illiger, 1815) (e.g., SCHALLER & VASCONCELOS, 1978; area is near the coastal plain, in the drainage basin of PINDER, 1997; MOURÃO et al., 2000; ANDRIOLO, 2005), the Lagoa Mirim. It is composed of a mosaic of open and boat counts for cetaceans (e.g., CREMER & SIMÕES- grasslands used for cattle ranching, extensive areas of LOPES, 2008; FLACH et al., 2008). Transect lines on irrigated ricefields, marshes, and some forest patches of the ground are used basically to estimate densities of native and exotic trees (mainly Eucalyptus spp.). The primates (e.g., PERES, 1997; GONZÁLEZ-SOLÍS et al., 2001; last area (D), located in southwestern Rio Grande do Sul SANTANA et al., 2008). Carnivores are inherently less in the municipality of Alegrete (30°05’S, 55°30’W), also abundant than herbivores (EISENBERG, 1999), and usually near the border with Uruguay, was studied between July hard to see, making it difficult to apply these methods. 2009 and December 2010. The landscape is composed Perhaps because of this, studies conducted in Brazil to of grasslands and some forest patches that occur mainly estimate the density of carnivores with transect lines along watercourses. Transects were established through such as that of ROCHA et al. (2008), with a fox species livestock ranches. Lycalopex vetulus (Lund, 1842) in the Cerrado Biome, Data collection and analyses. The study was are rare. On the other hand, some poorly known species based on line-transect methodology (BURNHAM et al., can be easily observed in their habitats, for example, the 1980; BUCKLAND et al., 1993). For this purpose, we Molina’s hog-nosed skunk, Conepatus chinga (Molina, established transects along secondary and farm roads: 1782). In southern Brazil, C. chinga is one of the most three at each site, ranging from 3 to 8 km (mean = 4.8 common medium-sized mammals occurring in open km) long. Transects were sampled during three to five areas, but despite this, studies of its density or relative consecutive nights, each month or once per season. Each abundance are still lacking. transect was repeated twice each night, with a minimum In this study, we aimed to estimate the density of interval of one hour between each round trip. As the C. chinga, as well as the relative abundances of other main goal of this study was to obtain density estimates medium-sized mammals, at two sites in the Pampas of C. chinga, it was not viable to invest in areas with few grasslands and two sites in the grasslands of the Atlantic animals, since a minimum number of records are needed Forest, comparing patterns of the composition of to perform estimates using the Distance Program. assemblages of medium-sized mammals. Therefore, 24 samples in each transect during six months were established as the minimum sampling effort at MATERIALS AND METHODS each site. Because we used existing roads, the transects were not linear and they usually followed the smoothest Study Area. This study was conducted in four relief. Sampling was carried out at night between 8:00 areas in southern Brazil located in two basic biotic pm and 03:00 am by car, driven at a constant speed formations, the grasslands of the Atlantic Forest and of 10 – 15 km/h; with one observer using a spotlight, the Pampas grasslands.