title: Statistical Evaluations of Variations in Dairy Cows' Milk Yields as a Precursor of Earthquakes.
abstract: Previous studies have provided quantitative data regarding unusual animal behavior prior to earthquakes; however, few studies include long-term, observational data. Our previous study revealed that the milk yields of dairy cows decreased prior to an extremely large earthquake. To clarify whether the milk yields decrease prior to earthquakes, we examined the relationship between earthquakes of various magnitudes and daily milk yields. The observation period was one year. In the results, cross-correlation analyses revealed a significant negative correlation between earthquake occurrence and milk yields approximately three weeks beforehand. Approximately a week and a half beforehand, a positive correlation was revealed, and the correlation gradually receded to zero as the day of the earthquake approached. Future studies that use data from a longer observation period are needed because this study only considered ten earthquakes and therefore does not have strong statistical power. Additionally, we compared the milk yields with the subionospheric very low frequency/low frequency (VLF/LF) propagation data indicating ionospheric perturbations. The results showed that anomalies of VLF/LF propagation data emerged prior to all of the earthquakes following decreases in milk yields; the milk yields decreased earlier than propagation anomalies. We mention how ultralow frequency magnetic fields are a stimulus that could reduce milk yields. This study suggests that dairy cow milk yields decrease prior to earthquakes, and that they might respond to stimuli emerging earlier than ionospheric perturbations.
authors.affiliation: Department of Animal Science and Biotechnology, Azabu University Graduate School of Veterinary Science, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan. h-yamauchi@azabu-u.ac.jp.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yamauchi
authors.affiliation: Hayakawa Institute of Seismo Electromagnetics Co. Ltd., UEC (University of Electro-Communications) Incubation Center, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan. hayakawa@hi-seismo-em.jp.
authors.forename: Masashi
authors.initials: M
authors.lastname: Hayakawa
authors.affiliation: Hayakawa Institute of Seismo Electromagnetics Co. Ltd., UEC (University of Electro-Communications) Incubation Center, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585, Japan. tomokei0929@gmail.com.
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Asano
authors.affiliation: Department of Animal Science and Biotechnology, Azabu University Graduate School of Veterinary Science, 1-17-71 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5201, Japan. ohtani@azabu-u.ac.jp.
authors.forename: Nobuyo
authors.initials: N
authors.lastname: Ohtani
authors.affiliation: Department of Human and Animal-Plant Relationships, Tokyo University of Agriculture, 1737 Funako, Atsugi, Kanagawa 243-0034, Japan. mo205684@nodai.ac.jp.
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Ohta
keywords: dairy cows; earthquake precursors; milk yields; subionospheric very low frequency/low frequency (VLF/LF) propagation; unusual animal behavior