A fine pair of antlers may be the most eye-catching attribute of the male red deer, but it is the quality of a stag's mating call that attracts females, according to new research. The study by Ben Charlton, a PhD student at Sussex University, found that ovulating red deer hinds show an active preference for "roars" that indicate a larger male. This study provides the first experimental evidence from non-human mammals that females use an acoustic cue to body size when selecting a mate, the university said. The research is published in the Royal Society journal Biology Letters .