Evidence of aquatic plant seed dispersal by eastern painted turtles (Chrysemys picta picta) in Massachusetts, USA

Direct or incidental ingestion of fruits or seeds by freshwater turtles can facilitate seed dispersal within and between bodies of water. Here, we evaluate Chrysemys picta (Eastern painted turtles) as a dispersal mode for hydrophytes and aimed to determine: 1) factors that drive diversity and abundance of egested seeds, 2) if certain regionally-common seed taxa more frequently occur in feces, and 3) assess the viability of seeds that passed through the turtle digestive system. Close to half of the turtles captured were found to egest seeds with a high proportion of these seeds (85-94%) apparently unaffected by the digestive process. In all, 5859 seeds (ranging from 1 to 1081 per feces) were recovered representing four plant taxa. Most seeds recovered from either pond, in terms of overall quantity, density, and frequency, were those of the locally-common Nymphaea odorata, followed by Nuphar variegata, suggesting these items may be actively targeted as food items. Analyses indicate neither turtle sex nor health had an effect on overall seed number or seed richness of feces. While germination levels varied by turtle and locality, defecated N. odorata seeds were capable of germinating at high capacities. When compared to control, however, trials suggest C. picta ingestion has an inhibitory effect. Our evidence supports a complementary bi-modal dispersal system implicating the mobile C. picta with hydrochory to enhance the transport of aquatic plants like N. odorata. The seed treatment and high mobility afforded by C. picta makes it an effective vector to overcome interpond limitations of hydrochory and ichthyochory, and potential seed mistreatment by some waterbirds.