Washington, May 20 : When trying to woo a mate fallow deer become hoarse, say scientists.

These animals can call for a mate more than 3000 times per hour during the peak mating season.

And their prolonged vocal efforts cause their call structure to break down, leaving them hoarse.

According to lead researcher Dr Alan McElligott, fallow bucks produce a call or groan, both to attract mates, and repel competing males.

During the study McElligott and Dr Elisabetta Vannoni from University of Zurich looked at a herd of fallow deer in Dublin, Ireland.

They recorded the bucks'' groans during three consecutive breeding seasons (2002, 2003, 2004), between dawn and sunset each day during October.

The team found that the pitch of groans was lowest during the peak and highest at the beginning and end of the rut or mating season.

Moreover, the duration of buck groans decreased as the rut progressed, probably due to exhaustion and the large weight loss (on average 25 per cent of body weight) that bucks experience at this time.

"Fallow bucks groan at very high rates during the rut. They also eat less, fight often, and lose a lot of weight," said McElligott.

"We think the changes in their groan structure are linked to this decline in body condition, and this information on their weakened state could be used by other bucks when deciding to challenge and fight.

"We believe that this phenomenon might be widespread in animals with similar strategies during the breeding season, in which males call repeatedly, reduce their food intake and consequently lose a lot of condition," he added.

The study appears in journal Animal Behaviour. (ANI)