Diet and Foraging Ecology of an Assemblage of Western Pond Turtles (Actinemys marmorata) Living in Two Northern California Urban Streams

Diet and foraging ecology studies of freshwater turtles are a way to determine the habitats they use. Over a 4-year period, we studied an aggregation of Western Pond Turtles (Actinemys marmorata) living in 2 urban streams in Northern California that carried urban stormwater runoff. By developing and using the gastric lavage procedure to retrieve stomach contents in the field, we found their diet was 31% less taxonomically diverse than that of turtles living in wildland streams. Further, >56% of their diet was the non-native Red Swamp Crayfish (Procambarus clarkii). In addition, these urban dwelling turtles foraged on the streamside terrestrial landscape and consumed previously unreported prey taxa. Moreover, by observing turtles forage and then collecting their stomach contents we found they incidentally ingested sand, soil, vegetation, and other nearby habitat of their prey. Our results show that habitat loss from stream maintenance program (SMP) activity to prevent urban flooding reduced their dietary taxonomic diversity by 69%. In addition, after SMP activity removed crayfish habitat the turtles abandoned foraging in one of the streams. Our results provide convincing evidence that A. marmorata is a carnivore rather than a dietary generalist.