The first population recapture study of indigenous coypus Myocastor coypus is reported in protected areas of Argentine pampas within a region where the species is hunted for food and fur. Quarterly live trapping at two sites captured a high proportion of all coypus present (96% of juveniles; 85% of adults, independently of season, site and sex). Survival (from mortality or emigration) was constant across sites and seasons, and higher for juvenile males than females (88% and 71%, respectively) and lower for adult males than females (45% and 81%). Most turn-over in numbers was replaced by births, and immigrating males tended to be the largest individuals present. Sex ratios were male-biased amongst juveniles and female-biased amongst adults. Taken together, these results are consistent with local resource competition in habitat rendered low in quality by crowding inside the locally protected areas. The indigenous coypu population matured more slowly, and to a smaller maximum body size, than coypus studied in introduced populations in North America and particularly in northern Europe. Cold European winters may have contributed to the evolution of precocious sexual maturity and larger body sizes in European compared with indigenous populations.
The only known introduction of a squirrel species into South America is the case of the Asiatic red-bellied tree squirrel Callosciurus erythraeus that was introduced in the Pampas Region of Argentina in 1970. To inform management programmes, we analysed the current distribution, expansion rate, and abundance of the red-bellied squirrel in Argentina, and identified invasion pathways. Apart from the first and main focus of invasion, three other invasion foci have originated as a consequence of intentional releases between 1995 and 2000. The main invasion focus already extends over >1300 km 2 , where estimated density averaged 15 ind ha −1 and numbers of squirrels may reach 100,000 individuals. The area invaded in the other three invasion foci varied between <1 and 34 km 2 and mean densities were around 3-5 ind ha −1 . Squirrel abundance and residents' attitude towards this introduced species in the main invasion focus make eradication unfeasible, though management actions such as control, containment and mitigation of damages should be undertaken. Eradication of the relatively small invasion foci must be immediately evaluated, with priority given to valuable conservation areas under high invasion risk.
Habitat use by coypu Myocastor coypus (Molina, 1782) was studied in agro-systems of 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 1995Mechongué (winter -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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