A new study shows the remarkable adaptability of the critically endangered Cat Ba langurs. Despite low genetic diversity, langurs have retained key genetic traits that help them survive in their isolated environment on Cat Ba Island in Vietnam. One of the remarkable adaptations is the ability to drink salt water. Due to its dramatic population decline, the species suffers from genetic impoverishment, high inbreeding, and potentially increased susceptibility to disease. Analysis of their genetic information shows that genetic diversity was maintained in functionally important areas of their genetic information. This allows Cat Ba langurs (Poliocephalic trachypithecus) to continue to adequately cope with changing environmental conditions. This extraordinary ability is a direct consequence of their isolated island habitat, where sources of fresh water are limited. Researchers show that changes in certain genes likely increased tolerance to salt water. These genetic adaptations allow langurs to cope with the high sodium content of salt water and thus contribute to their survival in this unique environment.