We measured survival, growth and body condition of eight hatchling cohorts of desert tortoises in captivity over 11 years to evaluate head-starting methods. At 11 years of age, seven times as many of the first cohort had survived than if they were free-living tortoises. Improvements in predator control, food and water supplementation and pen structure increased survival from seven to 10 times that under wild conditions. Annual survival averaged 96%. Carapace length (CL) increased 6.95 mm per year, similar to that of free-living tortoises. Annual growth rates varied with calendar year (possibly reflecting food and water supply), age, cohort (year hatched), mother, and in four dry years, with crowding. Most of the first cohort grew to a releasable size (CL >100 mm) by their ninth year. Body Condition Indices (CI) remained high, indicating little dehydration despite droughts in eight of the 11 years, because irrigation offered drinking opportunities. Head-started tortoises developed fully-hardened shells (>98% of adult shell hardness) earlier (10.1 vs 11.6 years), but at a larger CL (117 vs 104 mm), than did free-living tortoises. Selective feeding in head-start pens decreased subsequent germination of favored wildflower species, apparently by reducing the natural seedbank. Consequently we reseeded and irrigated each autumn to promote subsequent spring food supply. We irrigated in early summer to enable drinking and ensuing consumption of dry, dead plants and Bermuda grass hay, a supplement. These procedures can greatly improve juvenile survivorship, and increase numbers of hard-shelled, midsized juveniles to help augment wild populations.

中文翻译：

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领先的 Agassizi 沙漠陆龟 Gopherus agassizii 在自然野外围栏中实现了高存活率、高生长率和高身体状况

我们测量了 11 年来圈养的八组沙漠陆龟幼龟的存活率、生长情况和身体状况，以评估领先的方法。在 11 岁时，第一批乌龟的存活率是自由生活的乌龟的 7 倍。捕食者控制、食物和水补充以及围栏结构的改进使生存率从野生条件下的 7 倍增加到 10 倍。年生存率平均为 96%。甲壳长度 (CL) 每年增加 6.95 毫米，与自由生活的陆龟相似。年增长率因日历年（可能反映食物和水供应）、年龄、队列（孵化年份）、母亲和四年干旱年份而异，并且拥挤。第一批的大多数在他们的第九年增长到可释放的大小（CL > 100 毫米）。身体状况指数 (CI) 保持高位，尽管在 11 年中有 8 年发生干旱，但表明几乎没有脱水，因为灌溉提供了饮水机会。比自由生活的陆龟更早（10.1 对 11.6 岁）发育完全硬化的龟壳（> 成年龟壳硬度的 98%），但 CL 更大（117 对 104 毫米）。早起围栏的选择性饲养减少了受欢迎的野花物种的后续发芽，显然是通过减少天然种子库。因此，我们每年秋季重新播种和灌溉，以促进随后的春季食物供应。我们在初夏进行灌溉，以便饮用和随后食用干燥、死亡的植物和百慕大干草（一种补充剂）。这些程序可以大大提高幼鱼的存活率，并增加硬壳中型幼鱼的数量，以帮助增加野生种群。