Twenty-Third Annual Meeting and Symposium of the
Desert Tortoise Council, April 3-5, 1998
Abstracts

Sixteen neonates and 14 four and five-year old juvenile desert tortoises (Gopherus agassizii) were released from an in situ field enclosure in natural habitat at the U.S. Army's National Training Center in the central Mojave Desert of California where they were hatched and maintained. Juveniles were released in late Spring 1994 and 1995. Neonates were released within 2 weeks of emergence from their nests in Fall 1995 and 1996. I measured the straight-line distance traveled and direction of dispersal on the first day after release and after the period when there was no further movement away from a burrow and dispersal appeared suspended by winter hibernation or summer estivation. Mean distance traveled by neonates on the first day (48.5 ± 51.2 m) was further than by juveniles (36.0 ± 32.6 m) and three times as far on the final day (147.4 ± 102.8 m compared to 52.0 ± 70.6 m). Movements of neonates were longer and occurred over a shorter period, only 2 weeks compared to 4 weeks for juveniles before settling into a burrow with no further dispersal for the season. Mean circular angle of dispersion was similar for both groups on the first day: juveniles = 163° ± 76° and neonates = 168° ± 103°, and on the final day: juveniles 174° ± 73° and neonates = 222° ± 80°. There is a strong trend for dispersal to the southwest through southeast directions, but this was not significant (P = 0.05) due to low concentration. It is likely greater dispersal of neonates is facilitated by residual yolk sac lipid reserves. The reason for the uniformity of dispersal direction is not known at this time.