Obsessed with grasses?: The case of mara Dolichotis patagonum(Caviidae: Rodentia)

Abstract

The diet of mara (Dolichotis patagonum, Zimmeraman 1780) within the limits of Sierra de las Quijadas National Park (San Luis, Argentina) is described. Other studies regarding mara's diet showed that mara, feeds on different species of grasses and shrubs. However, there is controversy regarding the proportions of these items in the diet or whether this proportion varies seasonally. Considering mara's body size, anatomical features and physiology, we suggest that mara feeds on grasses in a greater proportion than shrubs and forbs. Moreover, giving that in this region precipitation varies considerably between seasons; it is also expected to find a correlation between the diet of mara and seasons. Fecal pellets of mara were collected during four periods including two dry, and two wet seasons. Relative frequency of each item in scats was determined by microhistological analysis. Results support the hypothesis that mara shows preference for grasses, despite they are less available than shrubs and forbs and that this preference remains constant through seasons regardless of the precipitation regime. The characteristics of mara's diet and the ecological implications of these findings are discussed.Key words: Dolichotis patagonum, diet, grasses, preference, Sierra de las Quijadas. RESUMENEn este trabajo se describe la dieta de mara (Dolichotis patagonum Zimmeraman 1780) en el Parque Nacional Sierra de las Quijadas (San Luis, Argentina). Los estudios realizados sobre su dieta indican que se alimenta de varias especies de gramíneas y arbustos. Sin embargo, existe cierta controversia acerca de la proporción en que se presentan estos ítemes, y si las mismas varían estacionalmente. En base al tamaño corporal de mara, y a sus características anatómicas y fisiológicas, se propone que mara consume una mayor proporción de gramíneas que de otras hierbas no graminiformes y dicotiledóneas en general. Además, esperamos una variación estacional de la dieta, correlacionada a una posible variación estacional en los recursos alimentarios asociada a las precipitaciones. Se colectaron muestras de heces correspondientes a cuatro estaciones en el parque, dos estaciones secas y dos lluviosas. Mediante análisis microhistológico se determinó la proporción de cada ítem medido como frecuencia de aparición en las heces. Los resultados apoyan la hipótesis de un consumo preferencial de gramíneas por parte de mara. Las gramíneas aparecen en mayor proporción en la dieta a pesar de estar en menor disponibilidad en el hábitat y sin que el régimen de precipitación tenga algún efecto. Se discuten las características de la dieta de mara y las implicancias ecológicas relacionadas con esta especie.

Mazama gouazoubira (Cervidae) diet during the dry season in the arid Chaco of Córdoba (Argentina)

“…The high proportion of succulents ingested in the study period, characterized by an elevated hydric deficit, is similar to that found in other studies with brocket deer in extreme dry areas like the boreal Chaco of Paraguay (Stalling, 1984) and the plains of La Rioja (Cartes Yegros, 1999), during the same season. The selection of succulent plants and cacti detected in this study is possibly related to the deer's water requirements (Stalling, 1984;Sombra and Mangione, 2005), which seems consistent, as the study was conducted during the dry season when water was limited. Our results suggest that leaves of woody plants, cacti and the fruits of both are important sources of food and water for the grey brocket deer in Chancaní Reserve, which allows them to survive in arid areas during a period of scarce resources.…”

Diet of the mara (Dolichotis patagonum), food availability and effects of an extended drought in Northern Patagonia (Mendoza, Argentina)

“…The ''grazer'' type attributed to the mara in the present study is justified by the high dietary proportion of grasses on both sampling sites, as can be observed in some other mara populations (Campos et al, 2001b;Sombra and Mangione, 2005). Nevertheless, it is important to recognize the relevance of low and tall shrubs as alternative food items for the mara during autumn-winter, when grasses become senescent.…”

“…Avoidance of a major grass in the vegetation, Panicum, and preference for scarce species such as the grass Bromus, the tall shrub Lycium and the low shrub Prosopis, are responsible for the higher Kufner et al, 1992;Campos et al, 2001b), Monte-Chaco ecotone (MC E, Sombra and Mangione, 2005), Monte-Espinal ecotone (ME E, Rodriguez and Dacar, 2008), and Southern arid Chaco (S CH, Chillo, 2007). Locations are ordered according to increasing rainfall and temperature.…”

“…Dietary shifts from a ''grazer'' in the wet season to a ''mixed feeder'' in the dry season, according to the classification of Bothma et al (2004), can be observed in some mara populations (Kufner et al, 1992;Sombra and Mangione, 2005). Differences found among the diets of mara populations occurring in different environments, representative of the distribution range of the mara, suggest an adaptive opportunistic feeding behavior, with a higher dietary relevance of shrubs as the environment becomes more arid and grass availability decreases.…”

“…The mara qualified as a ''grazer'' in Northern Patagonia during the wet and dry seasons (the present study), in Central Monte during the wet season (Campos et al, 2001b), and in Monte-Chaco ecotone during the wet season (Sombra and Mangione, 2005). On the other hand, the mara qualified as a ''mixed feeder that browses and grazes'' in Northern Patagonia during the drought (the present study), in Southern Monte during the wet and dry seasons (Bonino et al, 1997), in Central Monte during the dry season (Kufner et al, 1992), in the Monte-Chaco ecotone during the dry season (Sombra and Mangione, 2005), in MonteEspinal ecotone during the dry season (Rodriguez and Dacar, 2008), and in Southern Chaco during the dry season (Chillo, 2007). As was detected in the present study in Northern Patagonia, a decrease in the dietary proportion of grasses from the wet to the dry season can be also observed in the other populations where both seasons were studied (Fig.…”