The behaviour and survival of captive-born least weasels Mustela nivalis nivalis released in nature were reported in this study. Altogether 27 captive-born and six wild-caught weasels were equipped with radio transmitters and their survival was studied as a function of age and season. The daily mortality rate was generally higher in captive-born than in wild-caught weasels. The survival of captive-born weasels was highest if they were released during the summer and hence when they were young. Differences in the behavioural patterns of captive-born and wild-caught weasels were apparent. Captive-born weasels were often more visible in the field and were less timid than wild-caught weasels. Results suggest that to be successful, restocking of weasels should be done with young animals, which are preferably released during the season with abundant food resources.

From 1998 to 2000 we used radio telemetry to study habitat use by greater rheas Rhea americana in rural areas. Captive-born greater rheas preferred pastures to grasslands and did not use crops. No differences in habitat use were found between wild and captive-born greater rheas. Wild individuals preferred pastures, showed less preference for grasslands, and did not use crops. Rheas used pastures and grasslands for nesting but they did not use crops. No differences in nesting success was detected between these habitats. Our results show that agroecosystems that include grasslands and pasture production would strongly contribute to the conservation of this species. However, poaching must be controlled to ensure long-term persistence of wild populations of greater rheas.