Tomoyo Miura’s research while affiliated with Tokyo Metropolitan University and other places

Lunar phase and weather conditions are known to affect breeding activity of the Japanese common toad, Bufo japonicus formosus. However, information on toad activity during non-breeding season is very scarce. In this study, we investigated the influence of weather conditions and lunar phase on toad activity during the non-breeding season (April-November). Surface activity during the non-breeding season was monitored in Minami-ohsawa, Hachioji Tokyo from 2010 to 2014. The effects of weather conditions and the lunar phase on the number of toads captured were analyzed using Random Forests models (an ensemble machine learning method). Toads began to forage on the soil surface from late April and activity lasted until mid-November. Some meteorological variables such as temperature, wind, and atmospheric pressure affected toad activity, but the lunar phase, which is the most important variable in breeding activity, did not have an effect on surface activity of the toads during non-breeding season. However, differences were observed among adult males and females with respect to their response to meteorological variables: males responded positively to rainfall, but females did not. A distinct difference in the effect of temperature was also observed between adults and juveniles: juveniles became more active when daily minimum temperature was >15°C, although adults did not respond to an increase in temperature. Our results on sexual differences in weather-mediated activity and lack of the lunar phase effects during non-breeding season provide useful information for our understanding of life history of these toads.

The breeding activity of the Japanese common toad, Bufo japonicus formosus, was monitored in Yamakita-machi, Kanagawa Prefecture and Minami-osawa, Hachioji-shi, Tokyo, during 1992-1994 and 2011-2013. The breeding activity began in late February-mid March, and lasted for one to three weeks. The number of breeding toads captured per day varied, and the effects of the lunar phase on the breeding activity were analyzed using circular statistics. Rao's spacing test indicated that large reproductive events were not uniformly distributed along the lunar cycle (U=166.1, n=46, P<0.01); more events occurred around the new moon and very few events occurred around the full moon. In addition, analysis of a generalized linear model incorporating both lunar phase and weather conditions, such as temperature and rainfall as predictors, indicated that the lunar phase significantly affected the breeding activity, even after taking into account the effects of weather conditions. The adaptive significance of this lunar-mediated breeding activity of the toads is discussed. Reproductive synchronization in this species may be related to the behavioral response to the lunar cycle.