The Rio Cautário is a river in the state of Rondônia in western Brazil, flowing as a right tributary into the larger Guaporé River. The river's course is largely encompassed by protected areas, most notably the Rio Cautário Federal Extractive Reserve and the adjacent Rio Cautário State Extractive Reserve. These are conservation units covering a combined area of over 146,000 hectares of Amazonian forest, designed to support sustainable use by local extractive communities. This establishes the river's overall character as a remote, forested waterway within a protected ecosystem, suggesting a paddling experience focused on wilderness and natural observation rather than developed infrastructure. The presence of these reserves indicates that access and activities are likely managed, and paddlers should anticipate regulations aimed at preserving the environment and respecting the traditional practices of approximately 92 families living within the state reserve.

Specific details for paddlers, such as defined access points, recommended routes, seasonal water levels, water temperature, or on-the-water amenities, are not detailed. The river's setting within extensive extractive reserves implies that facilities for recreational paddlers are minimal to non-existent, and trip planning would require direct consultation with reserve management authorities to understand current access permissions, potential hazards, and any seasonal restrictions. The primary sights are the intact Amazonian rainforest and the associated wildlife it supports. The historical and cultural significance of the area is tied to its status as an extractive reserve, a model of conservation that integrates the protection of natural resources with the livelihoods of traditional local populations.