North Queensland Naturalist
North Queensland Naturalist 53: 1-16
Grant S. Turner
Abstract
Field observations of feeding behaviour, aggregations, and individual interactions in adult Johnstone River Snapping Turtles Elseya sp. are described. Turtles fed by day on windfall plant debris (leaves, flowers, fruits) at the water’s surface especially during the driest months and on filamentous algae and other vegetation on the substrate by day and night year-round. Turtles were recorded feeding on 17 different plant species but were very selective in what they consumed. Significantly more adult females were observed surface feeding compared to males; subadults and juveniles rarely engaged in surface feeding. Some turtles partially or completely emerged from water to seize food items. The nocturnal movement of adult turtles from the river into anabranches during the driest months to feed on algae growing on stones was recorded with some displacements exceeding 150 m in a single night. Adult female aggregations were recorded: (i) feeding beneath flowering and fruiting trees, (ii) in pools adjacent to nesting sites within days or weeks of nesting, (iii) as daytime ‘processions’ with all females heading in the same direction along the substrate, and (iv) repeatedly in clear shallow pool with minimal cover and no obvious food source. Adult male aggregations were also recorded in the context of feeding on the substrate while mixed-sex aggregations were recorded near in-flows where turtles selectively fed on plant debris washed into pools. Two apparent instances of courtship and one of mating were recorded.