Urbanization in mesic environments increases the frequency of terrestrial invertebrate water stress

Trophic interactions can be influenced by variations in water availability – a key resource for terrestrial life. Specifically, water-limited animals may increase food consumption to meet water, rather than energy or nutrient, demands. Agriculture and urbanization continue to alter the geomorphology and ecology of ecosystems; urbanization in cool, mesic climates tend to increase local temperatures and reduce water availability. However, the frequency of invertebrate water demand in urban areas is largely unknown. Thus, we made our observations at both sites with high and low impervious surface in a small and large city, and we compared those observations to those with clay and sand soil at a nearby oak-savannah. During June-August 2014, we observed the frequency with which arthropods were using wet and dry water pillows (pouches filled with a polymer that holds water, marketed for cricket care in the pet industry) placed in trees and on the ground at each location. Water demand occurs about 20% of the time (P < 0.001), and it is more pronounced at wetter sites, suggesting that invertebrates inhabiting these locales are more sensitive to reduced water availability. Furthermore, ants appear to be the most susceptible taxa to changes in water availability (P = 0.002), and about 38% of water stress response in arthropods was attributed to ants alone. Our data suggests that terrestrial invertebrates regularly experienced water stress in urban northwestern Ohio, and trophic interactions could be altered as a result.