Tandem Running and Coordinated Motion

Here are further explanations of our research topics and examples of the kinds of research we do.

Evolution of leader role in termite tandem runs

Termites show same-sex tandem-running behavior in both female-female and male-male pairs. How do they achieve such unusual pair movement coordination? Why can they exhibit such behavioral plasticity? Using state-of-the-art automated video tracking and trajectory analysis of movement behavior, we revealed that same-sex tandem running is achieved by one individual behaving like the other sex. Using data-driven simulations, we showed that this behavioral plasticity contributes to maintaining pair coordination. We also compiled published information about termite mating behavior across 72 species and demonstrated that termites have such behavioral flexibility because their ancestor did not have sex-specific leader-follower roles, so both females and males could lead or follow. Termites inherited this behavioral flexibility from an ancestral lineage and use it for same-sex tandem-running behavior.
Mizumoto et al., 2022 PNAS

Functional diversity of ant tandem runs

Ants also show tandem running. Unlike termites, they use this behavior to recruit nestmates to new nests or food resources. Despite the superficially similar behavior, we found distinct communication systems both between ants and termites and among ant species. For example, we provided clear evidence that tandem communication in two distantly related ant species, which is superficially similar and had been considered the same behavior, is fundamentally distinct. Combining network and information-theoretical analyses, we demonstrated that Temnothorax ants use tandem running to recruit additional recruiters, while Diacamma ants use tandem runs to move passive colony members. Our results show that simple social interactions can conceal great diversity across taxa, providing a new angle for studying the diversity of animal communication. Such evolutionary convergence, in which animals in different taxa use similar techniques for social interactions, provides an interesting opportunity to study the evolution of animal collective behavior.
Valentini et al., 2020 eLife
Mizumoto et al., 2023 iScience
Tanaka et al., 2023 STAR Protocols

Communication during termite tandem runs

In collective animal behavior, coordination is often achieved by feedback between leaders and followers; however, the contribution of each role is difficult to dissect in species showing high levels of coordination. We disentangled these roles by creating heterospecific tandem pairs of mating termites, a simple case of coordination in which the female leads the male on a search for a nesting site. Our experiments reveal that different species achieve a similar level of coordination by means of different mechanisms to transfer information between sender and receiver. We further show that this species-specificity is a result of sexual selection via mate preference and competition. In short, our study highlights cryptic interspecific variation in movement coordination, a source of variation for the evolution of novel social interactions.
Mizumoto et al., 2021 Proc R Soc B

We found clear evidence that mating pairs of two termite species do not rely on visual information for tandem movement coordination. Instead, they use vision to determine the timing of mate pairing, which is adaptively adjusted in a species-specific manner. Thus, termites use different information channels for different purposes: tactile and chemical cues for coordination and visual cues for obtaining global information.
Mizumoto and Bourguignon, 2023 Ecol Entomol

Search strategies of mating termites

How should females and males move to search for partners whose exact location is unknown? Theory predicts that the answer depends on the searching conditions, specifically what they know about where targets can be found. We demonstrated that termites adaptively switch search modes depending on their potential distance from their partners. We found that both sexes moved actively before finding partners, which means the locations of potential targets are completely unpredictable. In stark contrast, when pairs were accidentally separated during tandem running, they showed distinct sexually dimorphic movements, with females pausing for long periods while males paused only briefly and moved actively. Simulations confirmed that these movements increase the rate of successful encounters. The context-dependent switch of search modes is key to enhancing random animal encounters.
Mizumoto and Dobata 2019 Sci Adv

Furthermore, we showed that males of Coptotermes gestroi, which experience a variety of mate densities, adjust their movement speed according to the surrounding density of mates to enhance encounter rates with partners.
Mizumoto et al., 2020 J Anim Ecol

Optimal movement to search for mating partners

How can males and females enhance mating encounters when they have no idea of the locations of partners? Using simulations, we found that sexually dimorphic movements can achieve the highest encounter rates under some conditions, and demonstrated that this sexual dimorphism can evolve from an initial sexually monomorphic population. Our findings connect the evolutionary ecology of sex and the biophysics of movement, providing a novel mechanism by which sexual dimorphism can evolve.
Mizumoto et al. 2017 J R Soc Interface
Mizumoto and Dobata 2018 Sci Rep

Circadian rhythm in mate search of termites

Termites usually live within logs and underground with little fluctuation in light. Thus, they rarely show circadian rhythms. However, during the mating period, termite dispersers must search for mates outside the nests at the correct time. We found that unpaired termites show daily search-rest cycles and restrict searching activity to a certain period of the day by responding to photic cycles. Termites also showed weak periodic search-rest patterns under constant darkness.
Mizumoto et al. 2017 Popul Ecol

Adaptive values of same-sex pairing by termite males

From insects to primates, various animal species show same-sex sexual behaviors such as courtship, copulation, and pairing. However, this provides an evolutionary paradox because it cannot directly result in reproduction, and the occurrence of same-sex pairing is often explained by mistaken identity. In this study, I found that termite males formed same-sex pairs resembling monogamous colony-founding pairs and demonstrated how this contributes to their fitness. We found that pairs of male adults stopped searching for females and cooperatively established nests without females, although single males rarely ceased searching for mates. Males in such male-male partnerships had much higher survival rates than single males. Then, a male in a surviving same-sex pair invaded an incipient colony to kill the king and replace him. A mathematical model demonstrated that the observed strategy of establishing a male-male partnership instead of searching for females is advantageous when the risk of predation is high, even when colony fusion is rare. Pairing with another male isn’t the best option, but it gives mateless termites a chance to survive until they find a female, if that happens at all (Mizumoto et al. 2016 Anim Behav).