Redalyc.Distribution and Abundance of the Pampas Deer in San Luis
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Mastozoología Neotropical ISSN: 0327-9383 [email protected] Sociedad Argentina para el Estudio de los Mamíferos Argentina Dellafiore, C.M.; Demaría, M.; Maceira, N.; Bucher, E. Distribution and abundance of the Pampas deer in San Luis Province, Argentina Mastozoología Neotropical, vol. 10, núm. 1, enero-junio, 2003, pp. 41-47 Sociedad Argentina para el Estudio de los Mamíferos Tucumán, Argentina Available in: http://www.redalyc.org/articulo.oa?id=45710105 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Mastozoología Neotropical / J. Neotrop. Mammal.; 10(1):41-47 ISSN 0327-9383 ©SAREM, 2003 Versión on-line ISSN 1666-0536 DISTRIBUTION AND ABUNDANCE OF THE PAMPAS DEER IN SAN LUIS PROVINCE, ARGENTINA . C.M. Dellafiore1, M. Demaría2, N. Maceira2, and E. Bucher3 1 National Parks Administration, Alberdi 3016, 5800 Río Cuarto, Córdoba, Argentina. 2 National Institute of Agriculture and Technology, CC 17, 5730 Villa Mercedes, San Luis, Argentina. 3 National University of Cordoba, CC 198, 5000 Cordoba, Argentina. ABSTRACT. The pampas deer was originally distributed in the open grasslands of central and southern South America. In the Argentine Pampas, two small populations of the endemic pampas deer (Ozotoceros bezoarticus celer) subspecies persist in the eastern and western extremes of its original distribution. We used ground and aerial surveys in the semiarid grasslands of the south of San Luis Province to assess the status of this remaining popu- lation. Population density estimates ranged from 0.43 to 0.83 deer/km2 (488-1,224 animals). The female/male ratio indicated a predominance of females over males (1.23, 1.14, 1.35 and 1.54 in August and November of 1995 and February of 1996 and 1997 respectively). This study suggests that the pampas deer in Argentina is an endangered species, even consid- ering the population of pampas deer in Bahía Samborombón, in Buenos Aires province (with nearly 200 animals). RESUMEN. Distribución y abundancia del Venado de las Pampas en la provincia de San Luis, Argentina. El Venado de las Pampas (Ozotoceros bezoarticus) se distribuía originariamente en los pastizales abiertos del este y centro de Sudamérica. En los extremos este y oeste de la Pampa Argentina persisten dos pequeñas poblaciones de la subespecie endémicas O. bezoarticus celer. Empleamos censos aéreos y terrestres para conocer el estatus de la población en el pastizal pampeano semiárido del sur de la provincia de San Luis. La densidad poblacional estimada osciló entre 0.43 a 0.83 ciervos/Km2 (488 – 1.224 animales). La relación hembra/macho indicó un predominio de las hembras sobre los ma- chos (1.23; 1.14; 1.35 y 1.54 en agosto y noviembre de 1995 y febrero de 1996 y 1997, respectivamente). Nuestro estudio sugiere que, aun teniendo en cuenta la población presen- te en Bahía Samborombón - Buenos Aires (cercana a los 200 animales), el Venado de las Pampas en Argentina es una especie en serio peligro de extinción. Key words: pampas deer, pampas grassland, endangered species, Ozotoceros bezoarticus celer, aerial survey, ground survey. Palabras clave: venado de las pampas, pastizal, especie en peligro,Ozotoceros bezoarticus celer, censo aéreo, censo terrestre. Recibido 22 junio 2002. Aceptación final 25 noviembre 2002. 42 Mastozoología Neotropical / J. Neotrop. Mammal.; 10(1):41-47 C.M. Dellafiore et al. INTRODUCTION estimate population abundance, (b) determine the sex ratio, and c) identify the pattern of The pampas deer (Ozotoceros bezoarticus) was spatial distribution. originally distributed in the open grasslands (pampas) of South America, including central STUDY AREA and southwestern Brazil, southeastern Bolivia, Paraguay, Uruguay, and northern and central This survey was conducted on an area that Argentina (Jackson and Langguth, 1987). Of extends from 33º 55' S 66º 18' W to 34º 30' S the three recognized subspecies, Ozotoceros 65º 30' W in the General Pedernera Depart- bezoarticus celer is endemic to the Pampas ment, province of San Luis, Argentina. This region of Argentina, and is the only deer spe- region is characterized by sandy soils with cies directly associated with open grasslands slightly undulating relief and sand dunes that in that country. The Pampas grasslands origi- occupy large areas. Annual rainfall averages nally covered 500,000 km2 in east-central Ar- 450 mm and is concentrated in summer (Octo- gentina. However, since 1870 most of the area ber-April). Annual mean temperature is 17ºC. was turned into cropland following a massive The absolute maximum in summer is 43º C, immigration of European settlers. Conversion whereas the absolute minimum in winter is of native grassland to agriculture still contin- -15ºC (Capitanelli and Zamorano, 1972). ues in the more arid, western edge of the re- Although this area was originally included gion. Habitat loss, unregulated hunting, com- in the Espinal region (Cabrera, 1971), Leon petition with cattle (Jackson and Giullieti, and Anderson (1983) considered the area to be 1988), and transmission of cattle diseases the semi-arid, western extreme of the Pampas (Jungius, 1976) have caused the observed de- region. The dominant vegetation in undisturbed crease in pampas deer populations. Today the areas is open grassland dominated by cow grass species is included in the Red Data Book (Sorghastrum pellitum). Other associated (IUCN 1996), in the Red Book of Threatened grasses include Elionurus muticus, Mammals of Argentina (Diaz and Ojeda, 2000), Bothriochloa springfieldi, Chloris retusa, and is listed in CITES Appendix I. Schizachyrium plumigerum, Eragrostis lugens, At present, only two small isolated popula- Sporobolus subinclusus, Aristida spegazzini, tions of pampas deer remain in the Pampas Poa ligularis and Poa lanuginosa. A few region. The first is located in the coastal woody plants occur in the native grasslands, marshes and grasslands of the Bay of including patches of chañar (Geoffroea Samborombón in the province of Buenos Aires, decorticans), and isolated individuals of calden where a reserve of some 15,000 ha exists (Prosopis caldenia) and alpataco (Prosopis (Gimenez Dixon, 1991). The second is in our alpataco) (Anderson et al., 1970). study area in the south of San Luis province At present, the grasslands have been drasti- where the deer population is concentrated over cally altered by overgrazing, plowing, and in- 145,000 ha (Dellafiore et al., 2001). troduction of exotic grass species. Therefore, Animal population dynamics is a function of the landscape appears to be more heteroge- population density, age structure, sex ratio, and neous, with each area reflecting its manage- recruitment rate. The evaluation of population ment history (Anderson 1973; Anderson et density and distribution is important for the al.1978) development of management programs. The San Luis population of pampas deer remained METHODS almost unknown until Jackson and Langguth (1987) estimated 300 animals remaining in a The pampas deer is distributed over 400,000 ha, sample area of 300 km2. At present the conser- but its populations are concentrated on 145,000 ha vation status of the pampas deer in San Luis (Dellafiore et al, 2001). Aerial and ground sam- needs to be evaluated because of the growingly pling efforts were made over an area ranging be- 2 degraded habitat. Our objectives were to (a) tween 1,311 to 2,848 km . THE PAMPAS DEER IN SAN LUIS PROVINCE, ARGENTINA 43 Ground and aerial surveys a total width of 80 m in 1995 and 140 m in 1997. Two observers, one on each side of the plane, made The ground survey was conducted following the the counts, recording all the deer seen inside and internal roads in the area (fire lanes), whereas par- outside the transect boundaries. allel strip transects were used for the aerial survey. In both cases, we took a GPS point to record deer Abundance observations. Data were analyzed with “use of space” Relative abundance of deer seen via air and land of the GIS CAMRIS (Ecological Consulting 1993), were determined by the method of Järvinen and which allows the creation of percent convex poly- Väisänen (1975, 1976, 1977, 1981), which is used gons, where probability levels (P) specify the quan- for low-density species. This technique is an ampli- tity of observations that lie within them (thus, the fication of the strip transect method and considers 0.90 nucleus contains 90% of all the observations both the animals seen inside and outside the sam- in the nuclei). pling band. Variance was calculated when the num- Ground sampling ber of registered deer was greater than 25, while we used the jacknife method when less than 25 deer During 1995-96, the sample area was 1,520 km2, were counted (Miller, 1974). The confidence inter- distributed over three ranches or groups of ranches. val was calculated by a t-test (D± ta Ö and R- In 1997, the sampling area was increased to 1,870 1 DF). Abundance data estimated by air and land 2 km and covered seven ranches. Deer were counted sampling were compared via the Wilcoxon test for along transect lines (Järvinen and Väisänen, 1975, comparison of two samples (Sokal and Rohlf, 1980). 1976, 1977, 1981), travelling in a pick-up truck at a constant speed of 20 km/h. Each strip transect Dispersion was 17 km long; 16 independent transects were evaluated in 1995-96, and 30 independent transects We used the data obtained from aerial and ground were surveyed in 1997. Deer counts were conducted surveys to test the hypothesis of clumped disper- by two observers, looking at opposite sides of the sion of deer in each sampling season (c2 test). The road and counting all animals seen inside and out- dispersion index “I” was used to define the vari- side the transect (by means of separate registrations) ance/mean ratio (Tellerías, 1986).