Pongids are the family of great apes including orangutans, gorillas, and chimpanzees. They differ from other primates in having large canine teeth, especially in males, and using their long arms to swing through trees rather than walk on branches. All great apes have a wide chest, long neck, limbs, and head. They lack a tail and use their hands specialized for swinging to move in a semi-upright position. Great ape social structures vary from monogamous gibbons to chimpanzee and gorilla bands led by a dominant male. Their facial muscles allow for complex expressions and they are diurnal, building nests to rest at night.