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Ecological differences between two sympatric species of armadillos [Xenarthra, Mammalia] in a temperate region of Argentina

100%

Abba A. M., Cassini M. H.

Acta Theriologica

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2010

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tom 55

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nr 1

35-44

Morpho-physiological specialization related to foraging can act as constraints on behaviour and ecological patterns of abundance and distribution. We tested this prediction in two species (weeping or screaming hairy armadillos Chaetophractus vellerosus Gray, 1865 and mulitas Dasypus hybridus Desmarest, 1804) that represent the two subfamilies of armadillos (Dasypodidae, Xenarthra): Euphractinae and Dasypodinae. The first subfamily possesses a well-developed masticatory apparatus that is considered primitive within the Xenarthra, while Dasypodinae show reductions in various aspects of cranial morphology. We sampled signs (burrows and foraging holes) and captured both species on 34 farms randomly selected in the north-eastern Pampas region of Argentina. We analyzed several niche dimensions. The two species showed significant differences in habitat use, seasonal patterns and diet. Weeping armadillos were generalists in their diet and active throughout the year. They were associated with calcareous-sand soil, as expected for a burrowing animal of the deserts. They tolerated a wide range of environmental conditions. We found that mulitas are myrmecophagous, and that they demonstrated a reduction in body temperature and activity during the cold season. As expected from their geographical distribution, mulitas used mainly vegetation with high cover and were associated with humic soils. Niche segregation between the two species of armadillos appeared to originate from different degrees of dietary specialization.

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Population parameters of indigenous populations of Myocastor coypus: the effect of hunting pressure

100%

Guichon M. L., Cassini M. H.

Acta Theriologica

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2005

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tom 50

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nr 1

The coypu or nutriaMyocastor coypus Molina, 1782 is a semiaquatic rodent intensively harvested for fur in its native region. We studied population parameters at four sites differing in hunting pressure and characterised hunting activity in north-eastern Buenos Aires province, Argentina. Our interviews with hunters, local inhabitants and wildlife managers revealed that hunting is a cultural tradition in the countryside with the coypu being used as meat and, fur and the young occasionally used as pets. Quarterly live trapping captured a high proportion of all coypus present at each site. In sites with higher hunting pressure, low density of coypus was associated with high population losses and immigration. I n these sites the proportion of juveniles and pregnant females was similar to that obtained at sites with no hunting pressure. No foraging deficiencies were evident from diet quality analysis. Our results suggest that harvesting determines the dynamics of coypu populations in, this region where hunting pressure can be assessed by accessibility of hunting sites, their distance to urban or rural settlements, effective control of hunting, and human population density of the area.

3

Habitat use by coypu Myocastor coypus in agro-systems of the Argentinean pampas

80%

D'Adamo P., Guichon M. L., Bo R. F., Cassini M. H.

Acta Theriologica

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2000

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tom 45

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nr 1

Habitat use by coypu Myocastor coypus (Molina, 1782) was studied in agro-systems oí' the Pampas grasslands, Argentina. We analysed two dimensions of the habitat: perpendicular and parallel to the water source. The perpendicular dimension covered three distinct areas: border of the stream, interface, and crops, while the parallel dimension involved the use of different crop types. We worked at two study sites, Mechongué (winter 1995 - summer 1996) and Lujan (winter 1997). At Mechongué, we conducted Four seasonal samples using an indirect method of counting faeces to estimate abundance of coypu. Along the perpendicular dimension, coypus used the border significantly more than the interface and the crops. The relative use of the border increased over the study period. Parallel to the water source, crops were avoided and pastures were preferred, At the Lujan study site, we observed the behaviour of coypu by recording activity and use of cover types at different distances from the stream. Coypu spent most of their active time foraging (80.5%). Ninety-two percent of the bouts took place less than 4 m from the pond. Coypus did not move more than 10 m away from the pond and did not use the crops. These results disagree with the claim that coypus are a risk to croplands in their native range.

Ograniczanie wyników

3 Acta Theriologica

3 Cassini M. H.

2 Guichon M. L.

1 Abba A. M.

1 Bo R. F.

1 D'Adamo P.

1 2010

1 2005

1 2000

Ecological differences between two sympatric species of armadillos [Xenarthra, Mammalia] in a temperate region of Argentina

Population parameters of indigenous populations of Myocastor coypus: the effect of hunting pressure

Habitat use by coypu Myocastor coypus in agro-systems of the Argentinean pampas