in a cat's ear. Its function is unknown, though it may assist in filtering sounds. Nose Cats are highly territorial, and secretion of odors plays a major role in cat communication. The nose helps cats to identify territories, other cats and mates, to locate food, and has various other uses. A cat's sense of smell is believed to be about fourteen times more sensitive than that of humans. The rhinarium (the leathery part of the nose we see) is quite tough, to allow it to absorb rather rough treatment sometimes. The color varies according to the genotype (genetic makeup) of the cat. A cat's skin has the same color as the fur, but the color of the nose leather is probably dictated by a dedicated gene. Cats with white fur have skin susceptible to damage by ultraviolet light, which may cause cancer. Extra care is required when outside in the hot sun. Legs Cats are digitigrades, which means that they walk on their toes, just like dogs. The advantage of this is that cats (and other digitigrades) are more agile than other animals. Most animals have ground reaction forces (GRFs) at around two to three times their body weight per limb. But digitigrades have a higher GRF than other animals due to the increased weight on a smaller surface area, which would be about six times their body weight per limb. Toe tufts are commonly found on cats with medium to long coats. Clumps of fur that stick out at least beyond the paw pad can be considered tufts. In addition to soft paw pads, toe tufts help a cat to silently stalk its prey by muffling excess noise. However, outdoor cats tend to lose their toe tufts due to excessive abrasion on the rougher outdoor surfaces. This is in distinct contrast to indoor cats who spend most of their time walking on carpet or smooth floors. Cats are also able to walk very precisely. Adult cats walk with a "four-beat gait", meaning that each foot does not step on the same spot as any other. Whether they walk fast or slowly, a cat's walk is considered symmetric because the right limbs imitate the position of the left limbs as they walk. This type of locomotion provides a sense of touch on all four paws that is necessary for precise coordination. The cat's vertebrae are held by muscles rather than