TRACKS & TRACKING
By Michael White
Kefalonian Marine Turtle Project
Pen-Y-LÛ n, Mynydd Eilian, Ynys MÛ n, Cymru (Wales), LL68 9NNseaturtles@dial.pipex.com
Thanks to the David and Lucille Packard Foundation
and the Symposium Overseas Travel Fund
for assistance with travel funds
ABSTRACT: The track characteristics of Caretta caretta were measured in an attempt to identify unseen animals from their "footprints". These data were intended to corroborate evidence gathered during a radio telemetry study of inter-nesting habitat use and nesting site infidelity. The tracks from 60 emergences, nesting and non-nesting, made by 15 animals were measured. Two measurements proved to be fairly consistent over a number of emergences made by the same turtle. These were the inter-humeral span and the plastron groove in the centre of the track. A difference was apparent between the uptrack and downtrack, probably because the method of locomotion changes slightly; with the turtles tending to push with their hind flippers, either alternately or together, when going downhill. On the uphill journey, the motive power was provided by the forelimbs alone. The substrate affected the preservation of the track, with damp sand holding a more accurate pattern. The wet and dry zones were measured on the uptrack and downtrack, with three replicates taken whenever possible. The track patterns were easily destroyed by human activity, sandstorms and wave action. Three loggerheads were fitted with VHF transmitters during nesting but were only tracked for approximately 6 hours in each instance before transmissions were lost. The known life history for each animal was used to determine if nesting-site infidelity could have occurred. All suitable nesting beaches around the island of Kefalonia were surveyed weekly for signs of emergence. There was insufficient evidence to show conclusively that the same animal made different tracks, further work is planned for 1999.