Forests flooded by Amazonian white-water rivers, referred to as várzea, cover c. 400,000 km2 in Amazonia. This unique type of wetland is mostly underwater for 4–5 months per year, and even its highest areas are flooded for at least 1 month per year. As a result of this intense flooding, land animals such as the tapir Tapirus terrestris, lowland paca Cuniculus paca, and deer (Mazama spp.), although they can swim, are not present.
During our research, funded by the Mamirauá Sustainable Development Institute, Brazil, in c. 7,000 km2 of várzea within the confluence of two large rivers, the Japurá and Amazon, we have unexpectedly found the threatened yellow-footed tortoise Chelonoidis denticulata. This area lies within the Mamirauá and Amanã Sustainable Development Reserves, which are part of the Amazon Biosphere Reserve.
Between December 2013 and January 2015 we captured and returned 31 yellow-footed tortoises in this area. Eight tortoises were found at the peak of the flood, a period with a minimum water depth of 2 m, during which searches are only possible by canoe. Five of these tortoises were sheltering under branches and trunks and three were floating in the flooded forest. In monitoring this area during 2003–2014 we also recorded the hunting of at least 200 yellow-footed tortoises by local people.
Our findings suggest that the tortoises recorded are members of a population inhabiting the Amazonian várzea. The yellow-footed tortoise is one of the most hunted and traded species in Amazonia, highly prized as game meat and as a pet, and is consequently declining in several areas. As the only strictly terrestrial animal in the várzea, this tortoise is important for the subsistence and income of residents.
Our monitoring has shown that hunting of the yellow-footed tortoise in the várzea is most intense during the flooding season because the tortoises are more detectable when the water is high. The ease of detecting tortoises during this time also results in the capture of young tortoises, an age class normally protected in non-flooded forests because of the difficulty of detecting them.
Although categorized as Vulnerable on the IUCN Red List and included on Appendix II of CITES, the yellow-footed tortoise has rarely been considered in conservation projects, mainly because of the difficulty of detecting this species. Strengthening our knowledge of the major threats faced by tortoises in the várzea is the first step towards developing conservation and sustainable use strategies for this threatened species in this particular Amazonian wetland.