Management and relocation of nests of Podocnemis expansa (Schweigger, 1812) (Testudines, Podocnemididae) on the Crixás-Açu river, Brazil

Abstract

Podocnemis expansa nests in the sandbanks of the Crixás-Açu River in central Brazil during the dry season. With the return of the rainy season, the river banks are once again inundated, flooding nests and eggs and drowning hatchlings. This study evaluated relocation as an alternative to manage nests at risk of flooding. Forty P. expansa nests from four beaches of the Crixás-Açu were relocated to nurseries constructed in tanks filled with sand from the same river. Nine nests were covered with palm fronds to simulate shading conditions and to lower the incubation temperature. The base of the egg chamber was at a depth of 60 cm in all the nests. The duration of incubation varied for sunlit (49.1 ± 2.35 days) and shaded nests (51.7 ± 1.75 days), but did not change with nest position (center or edge of nurseries). Hatching success was 47.3 ± 13.6%, and did not vary significantly with sunlight/shade or nest position. The mean incubation temperature during the thermosensitivity period varied from 33 ± 1.56 °C to 34.1 ± 1.40 °C. The lowest mean temperature during the thermosensitivity period (31.9 ± 0.95 °C) and the highest proportion of males (up to 45% of hatchlings) were observed in a shaded nest. Most sunlit nests produced only females. The results suggest that relocation is a viable alternative in managing nests at risk of flooding during the rainy season in the Crixás-Açu. Moreover, artificial shading was shown to be an option to increase the proportion of males.Keywords: hatching, incubation, nursery, sex ratio, giant Amazon River turtle. Manejo e transferência de ninhos de Podocnemis expansa (Schweigger 1812)(Testudines, Podocnemididae) no Rio Crixás-Açu, Brasil ResumoDurante o período de maior vazante do rio Crixás-Açu na região central do Brasil, nos meses de setembro e outubro, Podocnemis expansa (tartaruga-da-amazônia) desova nos bancos arenosos que surgem nas suas margens. Com o retorno do período chuvoso em novembro é comum que as praias deste rio sejam inundadas afogando ovos e filhotes. Este trabalho avalia a transferência como alternativa de manejo dos ninhos que seriam naturalmente alagados. Foram transferidos 40 ninhos de P. expansa oriundos de quatro praias do rio Crixás-Açu para berçários construídos em tanques de alvenaria que foram preenchidos com areia oriunda do próprio rio. Nove ninhos foram cobertos com folhas de palmeira para simular o sombreamento e diminuir a temperatura da incubação. A base da câmara de ovos de todos os ninhos situou-se a 60 cm de profundidade. A duração de incubação variou entre os ninhos ensolarados (49,1 ± 2,35 dias) e ninhos sombreados (51,7 ± 1,75 dias), mas não foi afetada pela posição do ninho, se nas bordas ou no centro dos berçários. O sucesso da eclosão foi de 47,3 ± 13,6% e não foi afetado pelo sombreamento ou pela posição do ninho nos berçários. A temperatura média de incubação durante o período termossensitivo variou de 33 ± 1,56 °C a 34,1 ± 1,40 °C. Os ninhos ensolarados produziram 100% de fêmeas em sua maioria. Os resultados mostram que a transferênc...

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