A link between water availability and nesting success mediated by predator-prey interactions in the Arctic.

Although water availability is primarily seen as a factor affecting food availability (a bottom-up process), we examined its effect on predator-prey interactions through an influence on prey behavior (a top-down process). We documented a link between water availability, predation risk, and reproductive success in a goose species (Chen caerulescens atlantica) inhabiting an Arctic environment where water is not considered a limited commodity. To reach water sources during incubation recesses, geese nesting in mesic tundra (low water availability) must move almost four times as far from their nest than those nesting in wetlands, which reduced their ability to defend their nest against predators and led to a higher predation rate. Nesting success was improved in high rainfall years due to increased water availability, and more so for geese nesting in the low water availability habitat. Likewise, nesting success was improved in years where the potential for evaporative water loss (measured by the atmospheric water vapor pressure) was low, presumably because females had to leave their nest less often to drink. Females from water-supplemented nests traveled a shorter distance to drink, and their nesting success was enhanced by 20% compared to the control. This shows that water availability and rainfall can have a strong effect on predator-prey dynamics and that changes in precipitation brought by climate change could have an impact on some Arctic species through a top-down effect.