If you switch the sexes, where you give male choice. If a male sees another male with a preferred female, he will not go to that female. In birds, song learning is extremely imp in males, bc that"s how they get females its really useful and otherwise it will shrink. In meadow vole, male travel large distance to mate with females: when you look at the part involved in learning. In red deer males will roar to signal to other males that they are stronger (honest signal bc only big males can make the roar) In toads, the larger you are the lower the frequency you can produce: another constraint on what kind of signal is produced is what it needs to produce the nutrient (such as nutrient, in males that need carotenoids) If the males did not respond to it, they wouldn"t get any female: so once in a while they can be wrong and die from it.