This ability to drop their body temperature may help them last longer in rutting displays, says Gordon Grigg, emeritus professor at University of Queensland (UQ) School of Biological Sciences.
"Rutting involves very energetic daily display 'fighting' during which bulls contest ownership of a herd of females," Grigg said.
"By starting each day cooler, a bull can postpone heat stress, compete for longer, win more contests and potentially sire more offspring."
He said the ability of camels to drop body temperature in the mornings, invoking hypothermia, was once thought to be only a mechanism for conserving water in very hot dry conditions.
"But what we saw cannot be for saving water, we saw it only in winter, only in bulls during rut and, anyway, they had water freely available and used it routinely," he said after a detailed study in the Australian desert, where thousands of camels roam free -- descendants of herds once brought from Asian countries.
"By starting the day cool, a bull will enhance his capacity to store heat generated by the strenuous activity, thus prolonging the onset of heat stress.
"A bull that can sustain a contest for longer is more likely to win it and, so, control a herd of females and get more matings," Grigg said, according to an UQ release.
Competing bulls perform elaborate, ritualized and intense competitive behaviour including posing and strutting side by side, inflating and exposing the dulaa (a sac-like extension of the palate), jostling, running together and, not always but often, actually fighting, says Grigg.
The study has been published online in Biology Letters.