Calorie restriction preserves muscle tissue in nonhuman primates and rodents. Lemurs are primates belonging to the suborder Strepsirrhini. It used to hold 108 chimpanzees among 1,300 non-human primates. Lemurs generally have thin tooth enamel compared to anthropoid primates. Predators of primates include various species of carnivorans, birds of prey, reptiles, and other primates. Orangutans are among the most intelligent non-human primates. It infects only humans, other primates, and several types of mosquitoes. The behaviour has been found in humans, other primates, and dogs. Lemurs lack any shared traits that make them stand out from all other primates. Broca was one of the first anthropologists engaged in comparative anatomy of primates and humans. Elephant intelligence has been compared with that of primates and cetaceans. Oxytocin is synthesized by corpora lutea of several species, including ruminants and primates. They are the smallest of the simian primates. How these two groups relate to extant primates is unclear. The Natuna Island surili is one of the 25 most endangered primates on Earth.