Using Radio Telemetry to Assess Movement Patterns in a Giant Rhinoceros Beetle: Are There Differences Among Majors, Minors, and Females?

Abstract

The Japanese horned beetle Trypoxylus dichotomus is a peculiar example of a maledimorphic species that does not exhibit any alternative reproductive tactics. Typically, differences in male morphology correspond to marked differences in mating behaviors (Dominey 1984; Gross 1996). Large males tend to adopt aggressive, territorial tactics to attract and secure females, while small or otherwise inferior males try to mate via sneak or satellite tactics, or by dispersing away from dominant males (reviewed in Oliveira et al. 2008). Alternative reproductive tactics are expected to favor distinct male morphologies, because exaggerated weapons that confer fighting advantages to dominant males should impair dispersal and sneaking capabilities (Moczek and Emlen 2000; Madewell and Moczek 2006). Although alternative reproductive tactics have been described in a number of dimorphic beetle species (Eberhard 1982; Rasmussen 1994; Emlen 1997; Moczek and Emlen 2000), T. dichotomus major and minor males apparently do not have distinct mating behaviors. Large major males have a long, branched head horn and short, sharp thoracic horn that they use to pry rival males away from sap sites that attract females. Small minor males have short head and thoracic horns, yet they engage in direct combats with other males just as readily as major males, and do not fight in qualitatively different ways (Hongo 2003). Even though minor males engage in sneak-like behaviors, major males also sneak copulations, and the only male that is known to have successfully mated after sneaking was a major male (Hongo 2007). J Insect Behav (2013) 26:51–56 DOI 10.1007/s10905-012-9334-8