samples. This acid is a breakdown product of some amino acids by propionibacteria, which thrive in the ducts of adolescent and adult sebaceous glands. Because propionic acid is chemically similar to acetic acid, with similar characteristics including odor, body odors may be identified as having a pungent, cheesy and vinegar-like smell although certain people might find it pleasant at lower concentrations. Isovaleric acid (3-methyl butanoic acid) is the other source of body odor as a result of actions of the bacteria Staphylococcus epidermidis, which is also present in several types of strong cheese. Factors such as food, drink, gut microbiome and diseases can affect body odor, as can lifestyle and genetics. Function Animals In many animals, body odor plays an important survival function. Strong body odor can be a warning signal for predators to stay away (such as porcupine stink), or it can also be a signal that the prey animal is unpalatable. For example, some animals species, who feign death to survive (like opossums), in this state produce a strong body odor to deceive a predator that the prey animal has been dead for a long time and is already in the advanced stage of decomposing. Some animals with strong body odor are rarely attacked by most predators, although they can still be killed and eaten by birds of prey, which are tolerant of carrion odors. Body odor is an important feature of animal physiology. It plays a different role in different animal species. For example, in some predator species that hunt by stalking (such as big and small cats), the absence of body odor is important, and they spend plenty of time and energy to keep their body free of odor. For other predators, such as those that hunt by visually locating prey and running for long distances after it (such as dogs and wolves), the absence of body odor is not critical. In most animals, body odor intensifies in moments of stress and danger. Humans In humans, body odor serves as a means of chemosensory signal communication between members of the species. These signals are called pheromones and they can be transmitted through a variety of mediums. The most common way that human pheromones are transmitted is through bodily fluids. Human pheromones are contained in sweat, semen, vaginal secretions, breast milk, and urine. The signals carried in these fluids serve a range of functions from reproductive signaling