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Avaliação do sucesso de medidas de gestão de habitat na recuperação de populações de coelho-bravo e perdiz-vermelha, no vale do Rio Sabor
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Resumo(s)
A perdiz-vermelha e o coelho-bravo desempenham papéis preponderantes nos ecossistemas mediterrânicos, enquanto presas de inúmeros predadores e representam as espécies cinegéticas mais importantes em Portugal. Contudo, na Península Ibérica, estas espécies têm sofrido um declínio acentuado. No presente estudo, os esforços de recuperação dos efectivos populacionais focaram-se na implementação de medidas de gestão do habitat: realização de sementeiras em zonas de mato e construção de maroços. Foram intervencionadas três áreas, tendo-se definido uma área controlo para cada uma. Para avaliar o impacto da gestão na abundância relativa das espécies, as suas populações foram monitorizadas. A perdiz-vermelha foi amostrada com base em transectos lineares. Para o coelho-bravo, a amostragem foi feita com base na contagem de latrinas em transectos. Adicionalmente, foram monitorizadas as sementeiras e os maroços para verificar a ocorrência de ambas as espécies. O estudo teve ainda como objectivo uma comparação entre métodos de censo: pontos-de-escuta e batidas-em-seco para a perdiz; contagem de excrementos dispersos em pontos para o coelho. Foram obtidos poucos dados de perdiz, pelo que não foi possível avaliar o impacto da gestão de habitat nas suas populações. A abundância de coelho foi avaliada por um Modelo em 'Fasquia', sendo nas áreas geridas significativamente maior que nas áreas controlo. Contudo, não se encontraram diferenças entre épocas. A sua presença nas culturas foi constante ao longo dos meses. Uma Regressão Logística Binária revelou maior probabilidade de ocorrência quando a culturas estão na fase de 'crescimento' e 'floração'. Os maroços foram ocupados em apenas uma das áreas geridas. Quanto às metodologias de censo, considera-se que a batida-em-seco é o método mais eficiente na detecção de perdizes. Relativamente ao coelho, a contagem de latrinas funcionou bem, dado que permitiu um acompanhamento da sua dinâmica populacional.
The red-legged partridge and the wild rabbit play vital roles in Mediterranean ecosystems as prey of many predators and represent the most important game species in Portugal. However, in the Iberian Peninsula both species have been declining. In the present study, efforts to restore these populations have focused upon habitat management techniques: cover strips were planted to create a mosaic and artificial warrens were built. Intervention occurred in three areas, and a control area was defined for each one. To study the impact of this management scheme on the relative abundance of both species, their populations were monitored. Partridge populations were sampled using linear transects. As for the wild rabbit, the number of latrines per transect was counted. Additionally, planted strips and artificial burrows were monitored to ascertain the presence of both species. Another aim of this study was to compare sampling methodologies: call count points and absolute counts by prospecting the fields were carried out for the red-legged partridge; pellet counts were made for the wild rabbit. During this experiment, scant data was obtained on the red-legged partridge and, therefore, it was not possible to assess the impact of habitat management on these populations. A Hurdle Model was used to test the abundance of rabbit populations, which was significantly higher in managed areas in relation to control areas. However, no differences were found between sampling periods. The species presence on the planted strips was constant over the months. A Binary Logistic Regression revealed that the probability of rabbit occurrence is higher when the cultures are in the 'growth' and 'flowering' stages. The artificial burrows were only occupied in one of the managed areas. As for the sampling methods, absolute count is the most efficient way to sample partridge populations. For rabbits, latrine counts were a success as this method allowed access to the population dynamics.
The red-legged partridge and the wild rabbit play vital roles in Mediterranean ecosystems as prey of many predators and represent the most important game species in Portugal. However, in the Iberian Peninsula both species have been declining. In the present study, efforts to restore these populations have focused upon habitat management techniques: cover strips were planted to create a mosaic and artificial warrens were built. Intervention occurred in three areas, and a control area was defined for each one. To study the impact of this management scheme on the relative abundance of both species, their populations were monitored. Partridge populations were sampled using linear transects. As for the wild rabbit, the number of latrines per transect was counted. Additionally, planted strips and artificial burrows were monitored to ascertain the presence of both species. Another aim of this study was to compare sampling methodologies: call count points and absolute counts by prospecting the fields were carried out for the red-legged partridge; pellet counts were made for the wild rabbit. During this experiment, scant data was obtained on the red-legged partridge and, therefore, it was not possible to assess the impact of habitat management on these populations. A Hurdle Model was used to test the abundance of rabbit populations, which was significantly higher in managed areas in relation to control areas. However, no differences were found between sampling periods. The species presence on the planted strips was constant over the months. A Binary Logistic Regression revealed that the probability of rabbit occurrence is higher when the cultures are in the 'growth' and 'flowering' stages. The artificial burrows were only occupied in one of the managed areas. As for the sampling methods, absolute count is the most efficient way to sample partridge populations. For rabbits, latrine counts were a success as this method allowed access to the population dynamics.
Descrição
Tese de mestrado, Ecologia e Gestão Ambiental, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Mamíferos Coelho bravo Perdiz-vermelha Rio Sabor - Portugal Teses de mestrado