Marine Sponges, Other Animal Food, and Nonfood Items Found in Digestive Tracts of the Herbivorous Marine Turtle Chelonia mydas in Hawai‘i

Abstract

Although the usual diet of Chelonia mydas comes from algae and sea grasses (plant material), animal material has been found in samples taken over the past 35 yr. The small black-brown protein sponge Chondrosia chucalla resembles the alga Codium arabicum in size, color, and texture, and both grow next to each other on the reefs. We hypothesize that turtles are actively seeking and eating these sponges and not mistaking them for C. arabicum. Both protein and silica sponges occur in the diet of Chelonia, but only 6.8% of the time are eaten in addition to their usual plant diet. Thirty different kinds of other animals were found in the samples, including Cnidaria, Mollusca, Crustacea, Insecta, Echinodermata, squid, fish, tumor flesh, and other animals but in low frequency (5%). Most of the miscellaneous nonfood debris items were terrestrial leaves, plastic, paper, string, fibers, hair, and paint chips but also in low frequency (<7%). Among animal food items known to have nutritional value, the protein sponge C. chucalla could be contributing an important nutritive factor, but this needs further research.