 Genetic variations exist within fallow deer populations with variable antler growth, males that exhibited faster-growing antlers early in life are able to grow longer antlers without any significant cost, this shows that there is, in fact, phenotypic variation among fallow deer populations.Aggressive behaviour is often observed when individuals are seeking out mates, scarce resources, and even territories.Species that compete using their weapons usually engage when there is a mutual agreement, but if there are any noticeable asymmetries such as a broken or lost weapon this may alter the behaviour of an individual to engage in a fight.