Camera trap serendipity and citizen science point to broader effects of urban heat islands on food webs

Abstract Urban heat islands affect animal behavior broadly, but their effects on food webs are less understood. In November 2018, camera trap serendipity led to the detection of a red-tailed hawk (Buteo jamaicensis) preying upon an eastern worm snake (Carphophis amoenus amoenus) in Washington, D.C. – a previously undescribed trophic interaction. While red-tailed hawk activity is known to peak in cooler months, above-ground snake activity is expected to cease as winter approaches. We hypothesized this previously undescribed interaction was facilitated by the urban heat island effect prolonging the warm season in urban areas. To explore this hypothesis, we paired eastern worm snake observations from the iNaturalist platform with the monthly average temperatures from their nearest weather monitoring stations. Worm snake observations in areas at least 1 °C cooler than the average monthly urban temperature occurred between April and September. In contrast, observations in warmer, more developed areas (i.e. the urban heat island) occurred between March and December. Though other factors may be at play, we propose that relatively warmer winter temperatures found in urban ecosystems will continue to prompt novel trophic interactions as urban landscapes become more prolific.