Mate securing tactics and the cost of fighting in the Japanese horned beetle,Allomyrina dichotoma L. (Scarabaeidae)

TLDR: Males of the horned beetle show a bimodal frequency distribution with respect to horn size and the 2 morphs distinguished by this criteria showed different mate-securing tactics, with minors appearing to be relatively as successful at gaining copulations as majors but did so earlier in the diurnal cycle.

Abstract: Males of the horned beetleAllomyrina dichotoma L. show a bimodal frequency distribution with respect to horn size. The 2 morphs distinguished by this criteria showed different mate-securing tactics. Major males fought for possession of areas on oak trees that exuded sap. Fights escalated through a series of stereotyped encounters before entering the potentially damaging phase of close-quarter combat when the largest males in particular risked serious damage. Minor males, on the other hand, were never observed to fight with conspecific males, but retreated after making contact with them. Minor males arrived at sap sites earlier in the diurnal cycle than major males and so avoided them temporally as well as behaviourly. Minors appeared to be relatively as successful at gaining copulations as majors, but did so earlier in the diurnal cycle. Since females showed a slight tendency to remate on the same night, minors may lose fertilization opportunities if last male sperm precedence is high. Actual sperm precedence values are not know so the reproductive payoffs for the 2 morphs could not be assessed.