Rain,prey and predators: climatically driven shifts in frog abundance modify reproductive allometry in a tropical snake |
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Authors: | Gregory P Brown Richard Shine |
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Institution: | (1) School of Biological Sciences A08, University of Sydney, Sydney, NSW, 2006, Australia |
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Abstract: | To predict the impacts of climate change on animal populations, we need long-term data sets on the effects of annual climatic
variation on the demographic traits (growth, survival, reproductive output) that determine population viability. One frequent
complication is that fecundity also depends upon maternal body size, a trait that often spans a wide range within a single
population. During an eight-year field study, we measured annual variation in weather conditions, frog abundance and snake
reproduction on a floodplain in the Australian wet-dry tropics. Frog numbers varied considerably from year to year, and were
highest in years with hotter wetter conditions during the monsoonal season (“wet season”). Mean maternal body sizes, egg sizes
and post-partum maternal body conditions of frog-eating snakes (keelback, Tropidonophis mairii, Colubridae) showed no significant annual variation over this period, but mean clutch sizes were higher in years with higher
prey abundance. Larger females were more sensitive to frog abundance in this respect than were smaller conspecifics, so that
the rate at which fecundity increased with body size varied among years, and was highest when prey availability was greatest.
Thus, the link between female body size and reproductive output varied among years, with climatic factors modifying the relative
reproductive rates of larger (older) versus smaller (younger) animals within the keelback population. |
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Keywords: | Anuran Climate change Foraging Predator– prey Reptile Tropidonophis mairii |
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