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Factors influencing daily survival rates of Pacific treefrog tadpoles (Hyla regilla) in natural ponds.
Govindarajulu, Purnima*,1, Anholt, Bradley1, 1 University of Victoria, Victoria, British Columbia, Canada
ABSTRACT- Documented declines in amphibian populations have made it particularly urgent to develop methods for accurately estimating their survival rates in the wild, as well as identifying the factors influencing this rate. Numerous theories and experimental studies have identified factors influencing survival of tadpoles but few have been assessed under field conditions. In this study we obtained the first estimates of daily survival rates of tadpoles under field conditions using capture-mark-recapture methods and quantified the effect of abiotic and biotic factors on this survival rate. Specifically, we assessed the effect of temperature, intra-specific density and the presence of introduced competitors (Rana catesbeiana), on the survival rate of Pacific treefrog (Hyla regilla) tadpoles in Victoria, BC, Canada. We found that daily survival rates of tadpoles were relatively constant within a season and among years, but varied between ponds even if they were in close proximity to each other. We found that temperature and intra-specific density interacted strongly to affect survival rates. At low densities survival rates increased with temperature, but at high densities survival decreased with increasing temperature. We were unable to detect an effect of the introduced competitor over and above the variation accounted for by differences in temperature and intra-specific density in the ponds.
Key words: capture-mark-recapture, introduced species, daily survival rate estimation, Hyla regilla tadpoles