Feeding ecology of Ozotoceros bezoarticus: conservation implicationsin Uruguay

Abstract

ABSTRACT. The pampas deer (Ozotoceros bezoarticus Linnaeus, 1758) was in the recent past one of the most characteristic species in the Uruguayan grasslands. However, today the species is very rare, with small relict populations inhabiting in few ranches. To improve our understanding of pampas deer habitat use in modified ecosystems and propose management guidelines we analyzed the pampas deer feeding ecology at Los Ajos ranch. We performed an annual vegetation survey with the purpose to identify the main components of pampas's deer diet and the spatial overlap with livestock. Vegetation offer was characterized by predominance of monocotyledon plants; in three of the four sample periods. The preference values for the crops were positive for ryegrass in winter (0.24) and spring (0.54), the moments of greatest productivity of this pasture; while the rice crops values were negative all year round. The spatial overlap indexes with sheep show a complete exclusion, whereas with cattle the indexes gave values of 0.95 in spring to 0.14 in summer. The niche amplitude was significantly correlated with the spatial overlap levels with cattle. Pampas deer foraging behaviour is opportunistic, typical of mixed feeders. Conservation efforts should focus on implementation of management guidelines of agriculture and cattle breeding activities.KEYWORDS. Diet, habitat use, mixed feeders, niche overlap, pampas deer. RESUMO. Ecología trófica deOzotoceros bezoarticus: implicaciones para su conservación en Uruguay. El venado de campo (Ozotoceros bezoarticus Linnaeus, 1758) fue en el pasado reciente una especie focal de las pasturas uruguayas. Sin embargo, hoy día es una especie rara, con pequeñas poblaciones aisladas que ocupan establecimientos agropecuarios. En este trabajo se analizan aspectos de la ecología trófica en una población de venado de campo. El objetivo es: comprender la interacción entre esta especie y un ecosistema modificado por la actividad agrícola-ganadera. Se busca así proponer medidas de manejo de la población y del ambiente que ocupa. En este trabajo se identifican los principales componentes de la dieta y el grado de solapamiento espacial con el ganado doméstico, para ello se realizó un muestreo anual de la vegetación, se colectaron fecas de venado de campo y se analizó la distribución espacial de los distintos herbívoros que ocupan el establecimiento agropecuario. La oferta de vegetación se caracterizó, en tres de cuatro períodos de muestreo, por una predominancia de plantas monocotiledóneas. Los valores de preferencia para los cultivos fueron positivos para el ryegrass en invierno (0.24) y primavera (0.54), los momentos de mayor productividad de esta pastura; mientras que el cultivo de arroz mostró valores negativos de preferencia a lo largo de todo el año de estudio. Los índices de solapamiento espacial mostraron una completa exclusión con el ganado ovino, mientras que con el ganado bovino se obtuvieron índices de 0.95 en primavera a 0.14 en el verano. La amplitud de nicho tuvo una correlación significativa con...

Gross anatomy of the stomach of the pampas deer, Ozotoceros bezoarticus (Artiodactyla: Cervidae)

“…Regression lines for browsing ruminants in inferior line and for grazing ruminants in superior line. (RODRIGUES & MONTEIRO-FILHO 1996, COSSE et al 2009, the low values for the different measures depicted in Figs 6-8 are somewhat surprising. This discrepancy indicates that such anatomical measures alone cannot be considered sufficient for a classification of a ruminant species into a specific feeding type.…”

“…Similarly, CLAUSS et al (2009c) listed several examples of ruminants with typical 'grazer' morphology that ingest more browser material in their natural diet than expected from anatomical observations alone. Pampas deer feed on a range of mixed diets in the wild COSSE et al (2009). In particular, the size of the omasum can be suspected to be larger in free-ranging individuals.…”

“…There are a few species, however, such as the Père Davids deer, Elaphurus davidianus (Milne-Edwards, 1866), and the pampas deer, that consume comparatively large quantities of grasses in its natural diet (JACKSON et al 1980, JACK-SON & GUILIETTI 1988. COSSE et al (2009) considered the pampas deer to be an opportunistic species based on their foraging behavior, which was typical of an intermediate feeder. This was supported by the fact that the proportion of monocotyledonsdicotyledons, compared to other forage consumed by the pampas deer, varies throughout the year.…”

Demographic characterization and social patterns of the Neotropical pampas deer

“…The soils are predominantly gley soils. Altitudes range from −5 to 100 masl, the annual average rainfall is 1000 mm and the average annual temperature is 16°C (Cosse et al, 2009). The main land use activities are livestock (cattle and sheep) ranching, agricultural crops (rice, soy, wheat) and pasture (ryegrass).…”

“…This process is clearly visible in Uruguay, which is home to two endemic subspecies: O. b. arerunguaensis , represented by a population of around 1000 individuals in El Tapado (northern Uruguay); and O. b. uruguayensis , with less than 350 individuals, located at Los Ajos in southeast Uruguay (González et al, 2002). While populations of the other subspecies ( O. b. leucogaster, O. b. bezoarticus , and O. b. celer ) are found in protected areas in Argentina, Bolivia, and Brazil, the Uruguayan populations are located exclusively on private land where several agricultural activities are conducted (Jackson et al, 1980, Cosse et al, 2009;González et al, 2010). …”