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

100%

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.

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Taxonomy and distribution of the sigmodontine rodents of genus Necromys in central Argentina and Uruguay

84%

Galliari C. A., Pardinas U. F. J.

Acta Theriologica

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2000

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tom 45

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nr 2

The taxonomic status of the species of Necromys Ameghino, 1889 (= Bolomys Thomas, part), inhabiting the pampean region of Argentina and southern Uruguay is not clear. The two most recent systematic hypotheses both distinguish two species. Massoia and Fornes (1967) recognized Necromys obscurus (Waterhouse, 1837) with allopatric populations in southern Uruguay and southeastern Buenos Aires Province (Argentina), and N. benefactus (Thomas, 1919) distributed in a strip across northwestern-southwestern Buenos Aires Province. Reig (1987) argued that the populations of Uruguay and northwestern Buenos Aires Province belong to N. obscurus (including N. benefactus as a subspecies), while those of the southeast and southwest are referred to an unnamed taxon. To solve this problem, 152 specimens from Argentina and Uruguay were studied using morphometric data and qualitative characters. Craniodental variables were measured in 97 adult specimens of both sexes. Discriminant-function analysis among preestablished geographic groups and cluster analysis using Mahalanobis distances revealed the presence of two groups with contrasting morphological characteristics. The first group, which corresponds to N. benefactus, includes the populations from northern La Pampa, southern Santa Fé, and northwestern, centralwest, and southwestern Buenos Aires Province (Argentina). The second group, N, obscurus, includes the populations from Uruguay (N. obscurus obscurus) and from southeastern Buenos Aires Province (a new subspecies).

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The relationship among diet, alimentary tract morphology, and life history for five species of rodents from the central Argentine pampa

84%

Ellis B. A., Mills J. N., Kennedy E. J. T., Maiztegui J. I., Childs J. E.

Acta Theriologica

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1994

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tom 39

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nr 4

A suite of characters describing digestive tract structure has been hypothesized to reflect the relative degree of specialization of the digestive system of rodent species along a continuum from a proteinaceous diet of seeds and insects to a cellulosic diet of vegetation. Similarly, it has been proposed that life history traits might reflect diet and digestive tract structure, with the most opportunistic species consuming the most energy-rich diets of seeds and insects. The five members of the rodent assemblage of agroecosystems of the Argentine pampa were found to be omnivores and varied in the relative proportions of seeds, insects, and vegetation consumed. On a gross level, diet reflected life history; the most opportunistic species (smallest body size, highest fecundity, preference for disturbed habitats) consumed the most energy-rich diet, while the least opportunistic species consumed the most vegetation. However, comparative digestive tract structure was generally converse to that predicted, based on diet. Failure to observe predicted correlations may be due in part to seasonal variability in diet, lack of evolutionary relevance of crop habitats, or flaws in the underlying hypotheses. Alternatively, the observed variation in digestive tract structure may reflect the spectrum of variation encountered within an omnivore rodent guild rather than the degree of food specialization.

4

Distribution and use of burrows and tunnels of Chaetophractus villosus [Mammalia, Xenarthra] in the Eastern Argentinean pampas

84%

Abba A. M., Udrizar Sauthier D. E., Vizcaino S. F.

Acta Theriologica

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2005

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tom 50

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nr 1

Burrows and tunnels built byChaetophractus villosus (Desmarest, 1804) (hairy armadillo) were studied in a farming area located in the Argentinean pampas, Buenos Aires Province, Argentina. Fifty-six structures were selected and carefully excavated for this study. Data on diameter, form, and orientation of the entrance, angle, length, and depth of the galleries, and spatial distribution of the structures were recorded. The structures were separated into two types: simple and complex, both located in high terrain. Simple structures are shorter than complex ones and are built when animals are in search of food or as temporary shelters. Complex structures are built as home burrows. The orientation of the entrances of both kinds of burrows is related to the prevalent wind direction.

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Habitat selection by Burrowing Owls Athene cunicularia in the pampas of Argentina: a multiple-scale assessment

67%

Baladron A. V., Isacch J. P., Cavalli M., Bo M. S.

Acta Ornithologica

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2016

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tom 51

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nr 2

Human-induced habitat changes have been typically linked to negative effects on native species, but an increasing number of studies show that many species are unaffected by these changes or even benefited from them. The Burrowing Owl Athene cunicularia is a raptor species that has deserved special attention in recent years due to its capacity to live in a variety of natural and modified habitats. In this study, we analyzed habitat characteristics that determine the habitat selection of the Burrowing Owl at the nest-patch, territory and landscape scales in the Pampas of Argentina. We performed broadcasting call surveys to evaluate presence-absence of owls at random points. In addition, we measured habitat variables in the field and used satellite imagery to obtain land-use information. We used Generalized Linear Models to explore the influence of habitat variables on the probability of occupancy by Burrowing Owls. Our results indicate that Burrowing Owls demonstrate good ability to live in a wide variety of habitat types and with different disturbance levels in the Pampas. At the nest-patch scale, which includes the nest-site and the surrounding patch around it, the presence of owls was positively associated with the horizontal visibility and was influenced by the land-cover type. At the territory scale, the occurrence of owls was positively associated with the presence of active (non-vegetated) dunes and negatively with croplands. At the landscape scale, the presence of owls was negatively associated with the disturbance level and positively with the amount of borders between habitats. A unique multi-scale model containing variables of the three spatial scales was more robust to explain variation in Burrowing Owl occupancy patterns than any single-scale model. This would reveal the hierarchical nature of habitat selection by Burrowing Owls in the Pampas, comparable to that observed in North American populations.

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Winter diet of Great Pampa-finches Embernagra platensis in Guamini Lagoon, Argentina

67%

Montalti D., Ferman L. M., Camperi A. R., Soave G. E., Arambarri A. M., Darrieu C. A.

Acta Ornithologica

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2005

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tom 40

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nr 1

79-82

The diet of the Great Pampa-finch includes seeds rather than insects. Our objective was to study its diet during the winter season and, whenever possible, to record differences between the sexes in diet patterns. This species was studied at Guaminí Lagoon, Buenos Aires Province, Argentina. The stomach content of 38 adult birds was investigated. The analysis shows that the food eaten by E. platensis consisted of seeds (60%) (Chenopodiaceae, Asteraceae, Ciperaceae and Poaceae) and insects (39%) (Bellostomatidae, Dytiscidae, Curculionidae, Coccinelidae, Formicidae and Apidae). Males ate more insects and, overall, more items than females. These, in turn, consumed a greater amount of plants. Niche breadth values were 2.9 for males and 3.1 for females. The seeds encountered were those of plant species typically associated with the pampas.

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Long-term patterns of occurrence of Nosema locustae and Perezia dichroplusae [Microsporidia] in grasshoppers [Orthoptera: Acrididae] of the pampas, Argentina

67%

Lange C. E.

Acta Protozoologica

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2003

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tom 42

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nr 4

Ograniczanie wyników

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

Taxonomy and distribution of the sigmodontine rodents of genus Necromys in central Argentina and Uruguay

The relationship among diet, alimentary tract morphology, and life history for five species of rodents from the central Argentine pampa

Distribution and use of burrows and tunnels of Chaetophractus villosus [Mammalia, Xenarthra] in the Eastern Argentinean pampas

Habitat selection by Burrowing Owls Athene cunicularia in the pampas of Argentina: a multiple-scale assessment

Winter diet of Great Pampa-finches Embernagra platensis in Guamini Lagoon, Argentina

Long-term patterns of occurrence of Nosema locustae and Perezia dichroplusae [Microsporidia] in grasshoppers [Orthoptera: Acrididae] of the pampas, Argentina