Schell, D. M.. Water and Environmental Research Center,
Schwaner, T. M.. Dept. of Biology,

The role of marine-derived nitrogen in the nutrition of a reptile was investigated using isotope ratios. Adult venomous tiger snakes (Notechis ater) feed almost exclusively on Short-tailed Shearwaters on Mt. Chappell Island in Bass Strait, north of Tasmania. Several million birds return to nest in burrows during the austral summer during which time they are preyed upon by the snakes. Snakes are unable to feed upon adult birds or eggs, but feed upon the newly hatched chicks and continue for 6 - 7 weeks thereafter until chicks become too large. The snakes then fast for 40+ weeks until the next cycle begins. Juvenile tiger snakes feed on insects and small lizards and were anticipated to have low nitrogen isotope ratios typical of terrestrially-derived food sources. Blood samples from 27 snakes showed, however, that marine N is the predominant source for the island ecosystem with the smallest snakes showing del N-15 values in excess of 30 ppt. These high values are assumed to result from loss of the lighter isotope as NH3 from bird feces and incorporation of enriched N into plants. As snake length increased, del N-15 values decreased and approached typical marine values as snakes shifted to a diet solely of Shearwaters.
Day: Tuesday, Feb. 2
Time: Poster
Location: Sweeney Center
Code: SS32TU0116S