In the upper and middle reaches, the river flows through dense tropical forests; the rich flora and fauna are the subject of international research.[5] Discoveries of new species are frequent, such as of the Kapuas mud snake (Enhydris gyii), which was discovered in 2003–2005 by German and American herpetologists. This species is remarkable in that it can spontaneously change its skin color, similar to the chameleon.[12][13]