Resting Heart Rate of the Toad Bufo marinus: A Long-Term Study of Individual Differences and Environmental Influences

The average resting heart rate of eight Bufo marinus recorded for 24 h every second week during a 5-moperiod was found to be 13.5 ± 0. 08 b/min. These heart rates are considerably lower than those previously published. Reproducible resting heart rates could be attained only after aperiod of 6 h following preparation of the animalsfor recording of ECG. Sustained and significant differences not related to photoperiod, sex, or body weight were found between individuals. Feeding produced a large increase in heart rate for up to 3 d after a meal. Minor disturbances were produced by visual stimuli and substratum vibrations. It is concluded that a true resting value of heart rate in anurans can be obtained only if the animal has not had recent environmental disturbance, not undergone recent surgical procedures, and not been recently fed.