Mercury emissions from upstream golden mines in Pantanal (Brazil) have enormous potential for environmental impacts and wildlife health risks. Furthermore it is difficult to monitor such activities. Jaguars (Panthera onca) are broadly distributed apex predators, and recognized as a sentinel species. This feline possesses vital functions correlated to environmental factors, useful to detect environmental changes provoked by human activities, allowing evaluations of the ecosystem integrity. This research has the objective to evaluate the levels of mercury in hair collected from jaguars captured in conservation projects in Brazil.