Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Food selection by the guanaco (Lama guanicoe) along an altitudinal gradient in the Southern Andean Precordillera (Argentina)

100%

Puig S., Rosi M. I., Videla F., Mendez E.

Acta Theriologica

2014

tom 59

nr 4

Wild ungulates like the guanaco are exposed to important changes in climate and plant diversity along altitudinal gradients in the Andes Mountains, such as in the Southern Andean Precordillera where three phytogeographic provinces are present in altitudinal belts. The guanaco’s diet and food availability were seasonally analyzed using microhistological analysis and point-quadrat transects at six sampling sites, representative of the phytogeographic belts along the altitudinal gradient. Plant cover and diversity decreased with growing altitude. Richness of plant species was poorer at the summit than in the lower altitudes, whereas the proportion of species eaten by guanacos increased with altitude. The diet included 77 species. Grasses were preferred and shrubs were avoided all year round. The grass Poa spp. occupied more than 50 % of the diet at all altitudes. Grasses were the main dietary item even at low altitudes, where shrubs constituted the main food available. Decreasing generalism with descending phytogeographic belts agrees with the prediction for altitudinal gradients. The increase of diversity in the diet during the winter decline of plant cover at high and middle altitudes follows that expected from the optimal foraging theory. The winter decline of vegetation and the dietary shift from grazing to browsing proved to be stronger as altitude increases and the climate become more rigorous. Plant species richness, food scarcity, and climate severity are relevant variables to explain altitudinal and seasonal changes in the diet of adaptive ungulates in mountain environments, such as the guanaco in the Southern Andean Precordillera.

Architecture of Ctenomys mendocinus [Rodentia] burrows from two habitats differing in abundance and complexity of vegetation

88%

Rosi M. I., Cona M. I., Videla F., Puig S., Roig V. G.

Acta Theriologica

2000

tom 45

nr 4

Burrow systems of the fossorial rodent Ctenomys mendocinus Philippi, 1869 were studied in the Andean Precordillera. These burrows were linear, with laterals and branches forked off the main tunnel. Their size and architecture did not differ between sexes. Burrows showed a constant heading along the main tunnel, with a mean directional angle close to 0°, Most forks of the main tunnel were originated more than expected at plants, indicating a change of search pattern where plants were encountered. This behaviour suggests a tactic consistent with area-restricted search. These systems were compared with others of the same species located in a habitat with higher cover and structural complexity of vegetation, at the Mendoza Piedmont. Female burrows were larger and male burrows more bifurcated in the Precordillera. These burrows were more complex than those from the Piedmont, owing to the presence of secondary tunnels. The mean directional angle close to 0°, orthogonal branches and angles of ascent of laterals close to 40° were attributes shared by the systems of both habitats. C. mendocinus maintains a basic search pattern as an optimal forager, and increases the systems size and complexity probably as an adaptive strategy to optimize the foraging efficiency and minimize the prédation risk.

Ograniczanie wyników

2 Acta Theriologica

2 Puig S.

2 Rosi M. I.

2 Videla F.

1 Cona M. I.

1 Mendez E.

1 Roig V. G.

1 2014

1 2000

Wyniki wyszukiwania

Food selection by the guanaco (Lama guanicoe) along an altitudinal gradient in the Southern Andean Precordillera (Argentina)

Architecture of Ctenomys mendocinus [Rodentia] burrows from two habitats differing in abundance and complexity of vegetation