Files
Abstract
The Mojave Desert Tortoise population is declining and rearing neonate tortoises until they are more likely to survive (head-starting) is one strategy for population augmentation. In 2015 we began evaluating indoor-rearing to shorten the head-start period. We assigned 70 hatchlings to three treatment groups: indoor-reared (n=30), outdoor-reared (n=20), and directly released (n=20). Direct-release hatchlings were released in September 2015 and head-starts (outdoor- and indoor-reared) were captive for 7 months before release in April 2016. We evaluated size among groups before release and we monitored tortoises with radio-telemetry post-release until 27 October 2016. Indoor head-starts reached the size of 6-year-old wild tortoises by release but survival did not differ among treatment groups. Combined (all treatment groups) annual survival was 0.44 (95% CI, 0.340.58). Bird predation was the leading cause of mortality and tortoises had highest predicted survival (over 58 weeks) if they were >1.6 km from an active raven nest.