Studies done by scientists, at the
Fauna Communications Research Institute in
North Carolina, indicate that one of the reasons
cats purr could be because it helps their
bones and
organs and
grow stronger. They found that frequencies between 27 and 44 hertz were the dominant
purring frequency for a
house cat, and 20-50Hz for the
puma,
ocelot,
serval,
cheetah and
caracal. Almost all cats purr, including
lions and
cheetahs, though not
tigers.
Dr Elizabeth von Muggenthaler, the president of the institute, said: "Old wives' tales usually have a grain of truth behind them and cats do heal very quickly." Sound waves created at a particular frequency trigger the healing process in feline bones. Purring is believed to have a similar effect to ultrasound treatment on humans.
Dr von Muggenthaler also said that purring had to be advantageous to a cat to survive natural selection, but there seemed to be no obvious advantage for a cat merely to display contentment. A natural capacity for increasing bone growth and strength and reducing healing time was, however, "clearly advantageous".