10. Why do cats purr?
Whether it’s a tiger, a leopard or a house cat, all felines like to purr. They seem to do that in a bunch of different situations, such as: when they are stressed, when they are relaxed, when they are pet by humans, when they nurse their kittens, and sometimes during their sleep.
There is a theory which says that the purring promotes bone growth and it contains sound frequencies within the 25- to 150-Hertz range. This has been shown to improve bone density and promote healing. Because we know that cats conserve energy by being lazy and sleeping for long periods of time, purring may be a low-energy way to keep bones and muscles healthy, without being active and using them.