A population of Fowler's toads, Bufo fowleri, was studied between 21 April and 20 June 1992 in Medford, NJ. I obtained records of body size, body temperature, and focal samples of calling activity from 126 males over two months of chorus activity. Assuming that vocalizing is energetically costly, my primary purpose was to investigate whether calling effort was correlated with body size, growth rate, or chorus tenure. In addition, given that the body temperature of calling males over the breeding season varied by more than 10 C, these data provided an opportunity to identify correlations among body temperature and measurements of calling behavior. I made focal observations of calling activity on 16 nights. Mean nightly calling efforts were relatively constant throughout the study (range 10.8–14.2 sec of vocalizing per minute) with only 4% of the variation in individual calling effort explained by body temperature. Individual calling effort was weakly positively correlated to body size. Males tended to gain mass over 18 continuous nights of minimal chorus activity and to lose mass over 10 nights of continuous chorusing. Larger males were more likely to lose mass during these 10 nights. Growth rates were not correlated with calling effort. Chorus tenure was skewed; males vocalized a median of three nights (range 1–15 nights). Chorus tenure was not correlated with individual calling effort, body size or growth rate. However, chorus tenure was the only variable significantly correlated with mating success. In conclusion, although these data are consistent with the hypothesis that calling activity is energetically costly, it is unclear why certain males had higher chorus tenures than others. When compared to data on calling effort in other anuran species, B. fowleri appear to be calling near their physiological maxima.
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Vol. 2002 • No. 4