arXiv subjects

Ikkyu Aihara

Publications and source records attributed to Ikkyu Aihara.

6 recordsLinked to original sources

arXiv2026

Spatio-temporal structures in frog chorus with two species examined by laboratory experiments and mathematical modeling

Synchronization can be observed in various systems in physics and biology. The choruses of male frogs are known as an example of biological synchronization in which the well-organized temporal structure, i.e., anti-phase synchronization between neighbors, is realized. Given that male frogs produce sounds to advertise their territories to competitors, the dynamics of phases and spatial coordinates should be mutually coupled in the frog choruses. In this study, we examined the spatio-temporal dynamics in the choruses consisting of male Japanese tree frogs and other acoustic animals. First, we carried out playback experiments using actual frogs and observed that male Japanese tree frog synchronized in anti-phase with the stimuli of a similar frequency but did not synchronize with the stimuli of a much different frequency. Second, we modeled the choruses with two species as a system of coupled mobile oscillators and numerically evaluated how the spatio-temporal structure depends on the similarity of call frequencies. Numerical simulations of the model showed that (1) the two-cluster antisynchronization is established in the same species when the distributions of call frequencies are much different between two species and (2) the two-cluster antisynchronization is disturbed when the distributions of call frequencies are similar. These results highlight the occurrence of various spatio-temporal patterns in the proposed model, indicating the importance of repulsive effects with different weights on the variation of the spatio-temporal patterns.

nlin.AO↗

arXiv2026

Wavy synchronization in locomotion of train millipedes

The sophisticated control of many legs by millipedes and centipedes establish well-organized temporal structures such as wavy synchronization in their gate patterns. Quantification and mathematical modeling of such temporal patterns can contribute to the understandings of behavioral mechanisms in biological locomotion. In this paper, we investigated the temporal pattern and its mechanism in the locomotion of small millipedes, train millipedes (Parafontaria laminata armigera), by combining empirical data with a system of coupled phase oscillators. First, we performed behavioral experiments by using actual millipedes and characterized their locomotion patterns based on an order parameter capable of detecting wavy synchronization with a specific wavenumber k. Second, we proposed a phase oscillator model incorporating two phase shift parameters and estimated their suitable values by comparing numerical simulations of the model with the empirically derived wavenumber through the proposed order parameter. Consequently, we established a concise mathematical model reproducing not only the wavy synchronization of the train millipedes but also the other types of wavy synchronization. From the biological points of views, our result suggests that the asymmetric interaction between neighboring legs is a key factor in the sophisticated motion control of the millipedes, enabling them to maintain a specific wavenumber during forward walking.

nlin.AO↗

arXiv2026

Gradual emergence of temporal structures depending on the distance between neighboring callers in natural habitat of male treefrogs

Acoustic animals (e.g., insects and frogs) aggregate and produce sounds for mating. Well-organized chorus structures like call alternation and call synchrony indicate the importance of the precise control of call timing by individual males. However, the stable monitoring of multiple acoustic features in natural environments, especially the variation in call frequency, call timing and caller position, lacked in previous studies because of technical difficulties originating from the intense background noise, the existence of multiple sound sources and the wide area for monitoring. Here we have examined the spatio-temporal frequency structure in the choruses of wild treefrogs. First, we have performed field recordings by combining the sound-imaging system (25-66 units of sound-imaging devices) and microphone-array system (16-24ch of microphones) between 2021 and 2023. Second, we have analyzed the video and audio data and quantified the call frequency, call timing and caller position of each male, for 11 choruses with 66 males in total. Based on this large datasets, we have shown that synchronized behavior (call alternation) gradually emerges between neighboring callers depending on their distances even when the call frequency and chorus density moderately vary.

nlin.AO↗

arXiv2021

Excitatory and inhibitory interactions affect the balance of chorus activity and energy efficiency in the aggregation of male frogs: Theoretical study using a hybrid dynamical model

We theoretically study the role of excitatory and inhibitory interactions in the aggregations of male frogs. In most frogs, males produce sounds to attract conspecific females, which activates the calling behavior of other males and results in collective choruses. While the calling behavior is quite effective for mate attraction, it requires high energy consumption. In contrast, satellite behavior is an alternative mating strategy in which males deliberately stay silent in the vicinity of a calling male and attempt to intercept the female attracted to the caller, allowing the satellite males to drastically reduce their energy consumption while having a chance of mating. Here we propose a hybrid dynamical model in which male frogs autonomously switch among three behavioral states (i.e., calling state, resting state, and satellite state) due to the excitatory and inhibitory interactions. Numerical simulation of the proposed model demonstrated that (1) both collective choruses and satellite behavior can be reproduced and (2) the satellite males can prolong the energy depletion time of the whole aggregation while they split the maximum chorus activity into two levels over the whole chorusing period. This study theoretically highlights the trade-off between energy efficiency and chorus activity in the aggregations of male frogs driven by the multiple types of interactions.

nlin.AO↗

arXiv2019

Interaction Mechanisms Quantified from Dynamical Features of Frog Choruses

Interaction mechanism in the acoustic communication of actual animals is investigated by combining mathematical modeling and empirical data. Here we use a deterministic mathematical model (a phase oscillator model) to describe the interaction mechanism underlying the choruses of male Japanese tree frogs (Hyla japonica) in which the male frogs attempt to avoid call overlaps with each other due to acoustic communication. The mathematical model with a general interaction term is identified by a Bayesian approach from multiple audio recordings on the choruses of three male frogs. The identified model qualitatively reproduces the stationary and dynamical features of the empirical data, supporting the validity of the model identification. In addition, we quantify the magnitude of attention paid among the male frogs from the identified model, and then analyze the relationship between the attention and behavioral parameters by using a statistical model. The analysis demonstrates the biologically valid relationship about the negative correlation between the attention and inter-frog distance, and also indicates the existence of a behavioral strategy that the male frogs selectively pay attention towards a less attractive male frog so as to utilize the advantage of their attractiveness for effective mate attraction.

nlin.AO↗

arXiv2019

Landing Dynamics of a Seagull Examined by Field Observation and Mathematical Modeling

A seagull ({\it Larus crassirostris}) has a high ability to realize its safe, accurate and smooth landing. We examined how a seagull controls its angle of attack when landing on a specific target. First, we recorded the landing behavior of an actual seagull by multiple video cameras and quantified the flight trajectory and the angle of attack as time series data. Second, we introduced a mathematical model that describes how a seagull controls its speed by changing its angle of attack. Based on the numerical simulation combining the mathematical model and empirical data, we succeeded in qualitatively explaining the landing behavior of an actual seagull, which demonstrates that the control the angle of attack is important for landing behavior.

q-bio.QM↗