Crab-eating macaque 27% animal matter, 15% flowers and other plant matter, and 14% food provided by humans. This species exhibits particularly low tolerance for swallowing seeds. Despite their inability to digest seeds, many primates of similar size swallow large seeds, up to , and simply defecate them whole. The crab-eating macaque, though, spits seeds out if they are larger than . This decision to spit seeds is thought to be adaptive; it avoids filling the monkey’s stomach with wasteful bulky seeds that cannot be used for energy. It also can help the plants by distributing seeds to new areas: Crab-eating macaques eat
Crab-eating macaque of populations due to increased wild trade and rising levels of human-macaque conflict, which are reducing overall population levels despite the species being widely distributed. Each subspecies faces differing levels of threats, and too little information is available on some subspecies to assess their conditions. The "M. f. umbrosa" subspecies is likely of important biological significance and has been recommended as a candidate for protection in the Nicobar Islands, where its small, native population has been seriously fragmented, and is listed as vulnerable on the IUCN Red List. The Philippine long-tailed macaque ("M. f. philippensis") is listed as near threatened,