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Grand Teton National Park Report

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Temperature variation and species interactions were examined in small montane ponds in Grand Teton National Park during summer 1991. Temperature variation was pronounced, both over time and from place to place within one pond or across ponds. The magnitude of the temperature variation is such that it is likely to lead to large differences in the growth rates of poikilotherms that occupy these ponds. Growth rates determine body sizes at any one point in time. Tadpole body size influenced the probability of predation by salamander larvae in these montane ponds in Grand Teton National Park. Given the natural body size ratios of predator and prey (observed in 1991}, salamanders biased predation towards smaller tadpoles. Other predation experiments revealed that the salamander larvae biased predation towards tadpoles and away from damselfly naiads. This suggests that damselflies may experience lower predation by salamanders when in the presence of tadpoles than when in the absence of tadpoles. Several species, including snails, caddisfly larvae, and tadpoles were very abundant in some ponds, but could be essentially absent from others. These three taxa appear to share similar diets. A simple experiment revealed the Pseudacris tadpoles and the snails compete, and that presence of salamander larvae had no effect on the strength of their competitive interaction.