Trading off hatching success and cost in the captive breeding of Whooping Cranes

Captive breeding is an increasingly used conservation strategy for species with a high risk of extinction in the wild, but managing a captive breeding programme can be challenging if there is a deficiency in knowledge about the species’ breeding biology. A knowledge gap can make it difficult to evaluate different management options. For avian species, egg hatching success is a key demographic parameter, and data-logging egg technology can provide important information on optimal species-specific incubation conditions, which can help inform captive breeding practises and identify efficient captive management options. In the context of a captive breeding programme for endangered Whooping Cranes (Grus americanus), we investigated associations between hatching success and incubation conditions, including environmental parameters (temperature, relative humidity, and egg turning rate), and incubation type (artificial incubation; foster incubation by Sandhill Cranes, Grus canadensis; and Whooping Crane incubation). Finally, we considered both cost and breeding output in an analysis of incubation practises. We found that daily mean temperatures were negatively associated with hatching success, and that hatching success was highest with incubation under Sandhill Cranes. However, incubation by artificial incubators, rather than Sandhill Cranes, provided a trade-off between cost and breeding output that is likely to be acceptable to many captive programme managers. We encourage other captive breeding programmes to use innovations that help to increase potential release numbers for conservation translocations by considering biological and financial constraints.

圈养繁育（captive breeding）是针对野生灭绝风险较高物种的一种日益广泛应用的保护策略，但倘若对物种的繁育生物学存在认知匮乏，圈养繁育项目的管理往往颇具挑战。认知缺口会使得对不同管理方案的评估工作难以推进。对于鸟类（avian species）而言，卵孵化成功率是关键的种群统计参数，而蛋载数据记录技术（data-logging egg technology）可提供有关最优物种特异性孵化条件的重要信息，这有助于为圈养繁育实践提供参考，并筛选出高效的圈养管理方案。本研究依托濒危美洲鹤（Whooping Cranes, *Grus americanus*）的圈养繁育项目，探究了孵化成功率与孵化条件之间的关联，其中孵化条件涵盖环境参数（温度、相对湿度及翻卵率）与孵化类型（人工孵化、沙丘鹤（Sandhill Cranes, *Grus canadensis*）代孵及美洲鹤自身孵化）。此外，本研究在孵化实践分析中同时考量了成本与繁育产出两项指标。研究结果显示，日平均温度与孵化成功率呈负相关，且在沙丘鹤代孵条件下孵化成功率最高。不过，相较于沙丘鹤代孵，人工孵化器孵化可在成本与繁育产出之间取得平衡，该平衡方案或为多数圈养繁育项目管理者所接受。我们呼吁其他圈养繁育项目结合生物学与财务约束条件，采用有助于提升保护迁地放归项目中潜在放归个体数量的创新技术与方案。