Thermal responses of feeding rates differ across co-occurring predator species.

Changes in global temperature regimes are expected to transform species interactions in natural communities. However, predicting the consequences of warming on populations and communities is challenging because species interact with a range of community members. In theory, species should be adapted to their local temperature regimes, which might suggest a parallel shift across species interactions. But this may not hold if differences in traits (e.g., physiology or ecology) between sympatric species lead to concurrent differences in thermal responses. Here, we compare the thermal responses of feeding rates of six aquatic predator species from the same community feeding on the same prey species. Individual predators were experimentally exposed to temperatures ranging from 5 to 35°C spanning the temperature range of their native habitat. We found qualitative and quantitative differences in thermal response curves of per capita feeding rates across species that led to a shift in the rankings of species' per capita predation rates along the temperature gradient. Of the six species tested, two species demonstrated maximum feeding rates at intermediate temperatures, while feeding rates of the other four species increased monotonically. Additional experiments indicated the lethal temperatures for each predator were greater than the maximum temperature at which prey could survive, though for some, it was only greater by 2-3°C. Interestingly, this suggests that the decline in predation rates at higher temperatures predicted by past studies may not always be biologically relevant in natural systems. Furthermore, we found that the feeding rates of consumers differed in thermal optimum and sensitivity to changes in temperature. Consequently, increasing feeding rates with rising temperatures in one species could be offset by decreasing feeding rates in another. These results indicate the need to account for differences in the thermal per capita responses among predator species within communities to predict how temperature changes across seasons and years influence the interactions and dynamics of natural communities.