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Marine Turtle Newsletter 3:8, © 1977

More on the Tag Loss Problem

David Owens
Dept. of Zoology and Entomology, CO State University, Fort Collins, CO 80523 USA

In the course of an experiment being conducted at Cayman Turtle Farm, Ltd., 120 green turtles were tagged with monel steel tags from National Band and Tag Co. The 4.5 year old animals were then maintained in a cement tank of approximately 275 cubic meters capacity. The tags were affixed to the trailing edge of the rear flipper. During the first four weeks of the experiment approximately 5% of the tags were lost due to tearing out. Suddenly, during the fifth week, we noticed that a large number of animals were losing their tags. The tank was immediately drained revealing that only 35 of the original 120 were still tagged. In nearly all of these 35 the tags were corroded and falling off. Many of the lost tags were found on the bottom of the tank. The cross pieces on which the point of the tag hooks were all corroded away. In five other experiments in which plastic tags were used we never had a tag loss of more than 5%. It should be emphasized that these observations apply to high density tank situations and may not be indicative of what would occur in the wild. We could not however arrive at a reasonable explanation of this high corrosion rate that would have been caused by the confined tank situation.