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26th Annual Meeting and Symposium of the
Desert Tortoise Council, March 16-18, 2001
Abstracts
Comparative Dispersion of Juvenile and Neonate Desert Tortoises
A Preliminary Assessment of Age Effects
Lisa C. Hazard1 and David J. Morafka2
1Department of Organismic Biology, Ecology and Evolution, P.O. Box 951606, University of California, Los Angeles, CA 90095-1606
2Department of Biology, California State University, Dominguez Hills, Carson, CA 90747-0005
Dispersal by young tortoises released from semi-natural hatcheries could be affected by the age of the tortoise or the length of time spent within the hatchery before release. Older animals might be expected to remain closer to familiar territory than newly hatched animals. To test this, juvenile (6-8 years old) and neonate (< 2 months old) desert tortoises (12 per group) were fitted with radiotransmitters and released from the hatchery at the Fort Irwin Study Site (National Training Center, Fort Irwin, CA) in October 1999, and their movements tracked until all stopped moving (presumably hibernating) and no activity was observed, 34 days later. Juveniles and most neonates were hatched and grew up in FISS Pen 1, but all animals were released from around Pen 3, about 75 m west of Pen 1. In the first 34 days after release, neonates generally moved to the northwest, uphill and away from the release point, while juveniles moved northeast, in the direction of Pen 1. Total distance traveled and final linear distance from the release site did not differ between age groups. Neonates moved less frequently and settled into hibernation locations sooner than juveniles. All 12 juveniles and 11 of 12 neonates were still alive when transmitters were removed in the early spring; one neonate lost its transmitter shortly after release and its status could not be determined. Future releases from different locations around the pens will help determine whether differences between juveniles and neonates are due to philopatry of juveniles, which could have implications for proposed headstart programs.