One of the reasons that ants strongly influence nearly every terrestrial ecosystem on the planet is that they have diverse diets and opportunistic feeding habits. In cities, ants often feed on human foods, although they clearly do not have a long evolutionary history consuming potato chips and hot dogs. Assessing the nutritional ecology of urban ants can help us understand the consequences of a partially to largely anthropogenic diet for ants. We had previous data showing that ants living in Manhattan’s street medians had very strong preferences for fats (EVOO) over other food types (sugars, salts, water, amino acids). This pattern was particularly strong for Pavement Ants, Tetramorium sp.E. In this study, we assessed the diversity of local arthropod communities during feeding choice trials to get a sense of the relative prey availability across urban habitat mosaics. In particular, we focused on assessing the availability of arthropods that lacked physical or chemical defenses against ants in two cities-Manhattan and Philadelphia. We also conducted follow-up feeding trials near T. sp.E nests in street medians that assessed (i) the relative preference of ants for crickets relative to anthropogenic foods; and (ii) the relative preference of ants for four different types of cooking oil, with varying levels of complex amino acids.
Results/Conclusions:
We found that prey availability was significantly lower in street medians compared to parks and forests. Interestingly, we found that median habitats harbored significantly more arthropods with defenses against ants than those without physical or chemical defenses; this effect was absent from urban habitats with lower chronic environmental stress. The arthropods that had reduced abundances in medians relative to other urban habitats were the same groups that declined in Hawaii after exotic ant invasion. Feeding trials revealed that T. sp.E has a strong preference for insect prey over anthropogenic foods, and that they show no distinct preference for different types of anthropogenic fat sources. In sum, these results indicate that ants living in cities may be fat starved due to reduced availability of insect prey in these highly modified urban environments. Their rapid response to cricket baits suggests that ants may serve as an environmental filter in habitats with high levels of chronic environmental stress in cities. Our future work will assess predator-prey interactions between ants and other arthropods across urban habitats with varying levels of chronic environmental stress and the consequences of these interactions for ecosystem processes and services.