S
Sacculated
referring to a stomach with "saccules," or sack-like compartments, in which bacteria slowly break down cellulose, thereby providing more useable calories. Among the primates, only the Colobinae (colobus, langurs, and proboscis monkeys) have this characteristic. Cows and related animals also have sacculated stomachs.
Savannas
usually semi-arid plains regions covered with grasses and occasional scattered trees.
Semi-Terrestrial
referring to animals that spend much of their day on the ground but usually return to the trees to sleep. See arboreal and terrestrial. Eg: Chimpanzees
Septum
the soft tissue separating the two nostrils of a mammal’s nose.
"Selfish" gene theory
A model of evolution, a gene's eye view of natural selection. Genes are replicators, individuals are their vehicles. Replicators make copies of themselves. Successful replicators make more copies than unsuccessful replicators. Improved vehicles (bodies) promote their success.
Sexual Dimorphism
referring to anatomical differences between males and females of the same species. Non-human Primate males are usually significantly larger than females. This is especially true of semi-terrestrial monkeys and the great apes.
Sexual Skin or Swelling
a nearly hairless large swollen patch of skin around the genital area that becomes very prominent when females are in estrus. These areas swell with fluids and turn bright pink or red due to hormonal changes that occur in preparation for ovulation. The sexual skin also produces odors that excite males of the species. They become highly attentive to the females at this time. Sexual skins are found among many of the Old World monkey species as well as the chimpanzees and bonobos.
Subadult
the stage of maturation in which animals are beyond infancy and early childhood but are not yet fully grown.
Stereoscopic Vision
the ability to see things in three dimensions (3-D). Stereoscopic vision is what allows for true depth perception. See peripheral vision and binocular vision.
Symbol
a thing, such as a word, that can represent something else that is not here and now. The meaning of a symbol is arbitrary and is given by those who use it.