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A CASE OF SUCCESSFUL REINTRODUCTION MANAGEMENT OF AGOUTIS IN AN ATLANTIC FOREST RESERVE

Resumo

Reintroduction of extirpated populations is an increasingly popular conservation tool. However, many outcomes of those efforts are unknown and continuous monitoring is infrequent. Two common goals of reintroductions are to improve the long-term viability of wild populations; and to restore lost ecological interactions. Dasyprocta leporina is a scatter-hoarding rodent, a large-sized seed disperser. The reintroduction of its population at Tijuca National Park (RJ) started in 2010 aiming to restore lost ecological interactions. This study assesses the demography and spatial distribution of the reintroduced population and updates its status. Thirty-two individuals were released from semi-captive stocks in Rio de Janeiro from 2010 to 2014. Twenty-one of these survived the first 12 weeks after release. The population fluctuation was estimated through mark-resighting from November 2013 to March 2017 using a grid with 33 camera-traps in 133 ha. A larger grid, with 21 camera-traps in 880 ha working for one month in 2016 was used to investigate the spatial distribution of the species in the Park using occupancy models. Captured individuals were marked and resighting was carried out through 30 days of camera trapping after each capture session. Population size was estimated using a robust design Poisson-log-normal mixed-effects mark-resight model. We caught a total of 17 individuals, including 13 wild-born ones. We had a total effort of 12488 trap-days. The overall growth of the wild-born population was positive, with the estimated number of wild individuals increasing from 20 (95% CI: 16-25) to 34 (95% CI: 29-40) during this study and a peak of 40 (34 - 47) animals in September 2014. The single-season occupancy model, estimated from a total effort of 605 trap-days, suggested that the distance from the release sites was the main factor influencing the probability of the population occupancy. There was a low probability of occupancy (30%) compared to other studies. During the monitoring of 2013 to 2017, few released individuals were recorded alive. Therefore, most of the growth observed was due to the reproductive success of the wild population. The released area was supplied with regular baits to allow the demography assessment since 2013, which may have restrained the population spread in the study area. The concentration of the population may also have contributed to increasing population density and growth. This hypothesis is supported by the greater recruitment of individuals after a long period of continuous baiting between May and August 2014. Our results highlight the importance of long-term monitoring of the reintroduced population to assess the success of the species establishment and to evaluate management tools. Future actions should include experimental studies on the effect of baits in the occupancy of the space and continued monitoring. Because the reintroduced population is capable of unassisted growth, we conclude that the reintroduction has been successful on the medium-term. Thus, releases should be ceased in the study area. We were able to succeed in the agouti reintroduction with low release numbers and low-cost, and our experience provided a useful laboratory for understanding the dynamics of reintroductions.

Palavras-chave

Reintroduction, Agouti, Wildlife Management, Atlantic Forest, Demography, Occupancy.
 

Financiamento

FAPERJ, CNPq, CAPES, Funbio.

Área

Ecologia

Autores

Raíssa Sepulvida Alves, Caio Kenup, Catharina Kreisher, Katyucha Von-Kossel de Andrade Silva, Marcelo Rheingantz, Fernando A S. Fernandez