By recording and analyzing stutter-bark rates, the researchers showed that increases in stutter-barking steadily raised the female reproductive hormones responsible for ovulation.
"We never expected to see such a tight link between the vocalization and the hormone levels," Anderson said of the research, which has not yet been published in a journal.
"This came a real surprise."
The finding has big implications for breeding the rare cat, the researchers said.
The cheetah has an estimated adult population of only 7,500, according to the International Union for Conservation of Nature (IUCN).
The only known wild cheetah population outside of Africa today is a critically endangered group of fewer than a hundred in Iran.
"I think this just goes to show that telephone sex evolved before telephones," said co-researcher Fred Berkovitch, an ecologist at the San Diego Wild Animal Park.
"By documenting how sound makes animals horny, we hope to improve conservation-breeding programs."
(Related: "Cheetah Conservation Hopes Pinned on 'Ambassador' Cat" [June 17, 2004].)
Booty Call of the Wild
Using sound to jump-start reproduction is common among birds, but in mammals it is almost unheard of, experts say.
Male red deer are known to roar to advance the timing of ovulation in females, for instance.
But a male mammal using a signal to activate a reproductive cycle in a female has never been observed before.
Dan Blumstein, an ecologist at the University of California, Los Angeles, said the findings were "neat, but not unexpected."
The new research illustrates nicely how much can be done to improve breeding of endangered species by watching behaviors and studying hormones in the animals' waste, Blumstein added.
SOURCES AND RELATED WEB SITES