This 3030-sq-km biosphere reserve protects a good part of the wetlands around the lower reaches of two of Mexico’s biggest rivers, the Usumacinta and the Grijalva. These lakes, marshes, rivers, mangroves, savannas and forests are an irreplaceable sanctuary for countless creatures, including the West Indian manatee and Morelet’s crocodile (both endangered), six kinds of tortoise, tapirs, ocelots, jaguars, howler monkeys, 60 fish species and 255 bird species.
The Centro de Interpretación Uyotot-Ja visitor center, or ‘Casa de Agua,’ is 13km along the Jonuta road from Frontera, beside the broad, winding Río Grijalva. A 20m-high observation tower overlooks the awesome confluence of the Grijalva, the Usumacinta and a third large river, the San Pedrito – a spot known as Tres Brazos (Three Arms). Boat trips (two hours, up to seven people M$1000), offered by a changing schedule of local communities on rudimentary lanchas, are available into the mangroves, where you might see crocodiles, iguanas, birds and, with luck, howler monkeys. The boats are rudimentary at best, so it's better value with a group. Note: these operate daily (while the Centro de Interpretación Uyotot-Ja does not). March to May is the best birding season.
From Villahermosa, ADO and Cardesa buses service Frontera (near the site of conquistador Hernán Cortés’ 1519 first battle against native Mexicans), from where colectivos run the 15-minute trip to the reserve (M$25). A taxi from Frontera costs around M$100.