|
Radar
Tag Studies Document Early Movement and |
|
December 6, 2000-- Aiken, SC--Miniature harmonic radar reflector tags weighing about 4 mg, have been attached to the posterior carapacial margins of five newly-hatched eastern box turtles (Terrapene carolina carolina), and were used to track the movements and behavior of these four hatchlings during the first two months of their life. The study is still on-going and radar tracking contact is still being maintained with three of the four hatchlings. Hatchlings emerged from a nest in an ecotone between an urban forest and a suburban backyard in Aiken, South Carolina, USA. Hatchlings were collected when they emerged on 20 September, 2000 and were held in captivity until tags could be attached and the hatchlings released on 14 October, 2000. Immediately following release at the nest site, all five hatchlings moved in the same general direction towards a large diffuse patch of Liriope, an exotic grass used widely as an ornamental in suburban landscaping. Over the next two months, these hatchlings remained in or close to that patch of ornamental grass and were almost always found either close to or actually dug-down into the root/stem basal mass of individual grass clumps. Hatchlings were found to move throughout the patch by “leap-frogging” from the base of one grass clump to another. At one time, a hatchling was found about 2 cm above the surface of the soil in the midst of the grass clump. When the radar detector device passed overhead, this hatchling tumbled back head-first down into the grass clump and disappeared, much like an aquatic turtle diving off a basking log! As of November 29, 2000, no hatchling has moved more than 5 m from the nest site. Despite overnight temperatures as low as the mid 20o’s F one hatchling moved over 1.0 m from one grass clump to near another grass clump on two occasions in mid-November. Although an effort has been made to not dig-down to observe the hatchlings directly and thus risk disturbing them, one such attempt revealed the hatchling in a particularly cold spell of weather to be pushed down into mineralized soil with less than 1.0 cm of leaf litter over the dorsal-most portion of its carapace. Computer-activated sealed temperature sensors have now been placed at the locations of these hatchlings, with some sensors positioned on the surface above the point of the hatchling’s signal, and others being buried as close as possible to the location of the hatchling itself, without running the risk of disturbing the animal. As of November 30, 2000, tracking contact continues to follow four of the original five hatchlings. The missing hatchling was almost certainly taken by a predator (probably a raccoon) one day after release, when a large pit was found to be dug overnight at the last location where this hatchling’s signal had been detected the day before. This study is part of an on-going radio-telemetry study of free-ranging eastern box turtles occupying the ecotone between this urban forest and the backyards/lawns of suburban neighborhoods adjoining the wooded area. The eggs from which these hatchlings emerged were laid by a female turtle which has carried a 60-65 g box-shaped transmitter bolted to the rear of her carapace for over 11 years! Apparently, male box turtles are more clever and adept at copulating with turtles carrying such transmitters on the rear of their carapace than many of us had imagined. This study is being supported in part by the Financial Assistance Award Number DE-FC09-96SR18546 from the U.S. Department of Energy to the University of Georgia Research Foundation and by grants-in-aid of research from the Trinity Presbytery and Office of Environmental Justice of the Presbyterian Church (USA). For further information, please contact Dr. I. L. Brisbin, Savannah River Ecology Laboratory, Drawer E, Aiken, South Carolina 29802, USA; telephone (803) 725-5668; fax (803) 725-3309; e-mail brisbin@srel.edu.
|