Nicobar Islands in the Bay of Bengal. This primate is a rare example of a terrestrial mammal that violates the Wallace line. Introduced range The crab-eating macaque is an introduced alien species in several countries, including Hong Kong, Taiwan, West Papua, Papua New Guinea, New Britain, New Ireland, New Caledonia, Solomon Islands, Fiji, Tonga, Samoa, Nauru, Vanuatu, Pohnpei, Anggaur Island in Palau, and Mauritius. This has led the Invasive Species Specialist Group of the International Union for Conservation of Nature to list the crab-eating macaque as one of the "100 of the World's Worst Invasive Alien Species". In Mauritius, it is a threat for the endemic and endangered Roussea simplex, as it destroys its flowers. It also hinders germination of some endemic trees by destroying most of their fruits when unripe and competes with the endemic endangered Mauritian flying fox for native fruits. Where it is not a native species, particularly on island ecosystems whose species often evolved in isolation from large predators, it is a documented threat to many native species. The immunovaccine porcine zona pellucida (PZP), which causes infertility in females, is currently being tested in Hong Kong to investigate its use as potential population control. Relationship with humans Crab-eating macaques extensively overlap with humans across their range in Southeast Asia. Consequently, they live together in many locations. Some of these areas are associated with religious sites and local customs, such as the temples of Bali in Indonesia, Thailand, and Cambodia, while other areas are characterized by conflict as a result of habitat loss and competition over food and space. Humans and crab-eating macaques have shared environments since prehistoric times, and both tend to frequent forest and river edge habitats. Crab-eating macaques are occasionally used as a food source for some indigenous forest-dwelling peoples. In Mauritius, they are captured and sold to the pharmaceutical industry, and in Angaur and Palau, they are sold as pets. Macaques feed on sugarcane and other crops, affecting agriculture and livelihoods, and can be aggressive towards humans. Macaques may carry potentially fatal human diseases, including herpes B virus. In Singapore, they have adapted into the urban environment. The macaques have also developed a reputation for actively stealing items from humans (cameras, eyeglasses, hats, etc.), then refusing to return their stolen goods until given food in return. This unique form of kleptoparasitism (known as "robbing and bartering") has primarily been observed in smaller groups