The heart of an animal keeps moving for the rest of its life, but it moves irregularly with small fluctuations every beat. Regarding the fluctuation of each beat (heart rate variability), it is said that the parasympathetic nervous system is involved in the high frequency component, and both the sympathetic nerve and the parasympathetic nerve are involved in the low frequency component.Autonomic nervous function can be evaluated by this fluctuation analysis (frequency analysis), and it is used in many fields as an index of stress in the case of humans.

　So far, attempts have been made to evaluate autonomic nervous function from the heart rate variability of dogs as in humans.However, since the resting respiratory rate is small and the respiratory rate fluctuation and individual differences are large, it has been difficult to analyze the heart rate variability using the frequency domain as an index.

　In this research, we focused on heart rate variability analysis using a time domain that is different from the frequency domain index. We have developed a system to analyze distribution fluctuations of plots in dogs in a short time by using a method (Lorentz plot) that expresses the time interval for each beat as points on a graph (using a wearable sensor manufactured by Sharp Corporation).As a result, it has become possible to evaluate "the state of the dog's mind" such as rest or tension in real time from the heartbeat information of the dog in the artificial rest or tension.

　Such a system for analyzing the state of an animal can be a tool for humans to understand the mental state and stress of a dog.In addition, if changes in physical condition can be detected quickly by observing for a long period of time, it is expected to be applied to the veterinary field such as dog health management, early detection of diseases, and evaluation of treatment.