Abstract:

Aim: In response to the severe challenge of ongoing global biodiversity decline, reintroduction serves as a vital conservation strategy for rescuing endangered species and restoring regional biodiversity. Pre-release acclimation plays an indispensable role in this process, as it prepares captive-bred individuals—which often lack survival experience in the wild—for release. Foodbased enrichment constitutes a core element of such training, primarily by modifying food types and simulating natural foraging environments to enhance animals' adaptability to local food resources. However, research on the dynamic process of food enrichment and its quantitative evaluation remains scarce. To assess the adaptability of the Crested Ibis (Nipponia nippon)to coastal wetland foods and to explore the application of behavioral methods in evaluating the effectiveness of acclimation,this study examined the Crested Ibis undergoing acclimation at the Jiangsu Yancheng Wetland Rare Birds National Nature Reserve. 

Methods: We conducted 37 diet-shifting experiments during July and August 2023. We employed the all-occurrence sampling method to record the diversity of coastal foods consumed and the frequencies of associated behaviors (observing,probing, ingesting). Secondly, we used generalized linear models (GLMs) to analyze foraging behavior, foraging activity, and adaptation time in the diet-shifting experiments. Counts of observing, probing, and ingesting behaviors per round were initially modeled with Poisson regression, switching to negative binomial regression if overdispersion was detected. Normality of daily total foraging mass, foraging proportion, first probing time, and first ingesting time was assessed using the Shapiro–Wilk test. Normally distributed data were analyzed with linear regression, right-skewed data with Gamma regression, and left-skewed data with inverse Gaussian regression. 

Results: The results revealed a clear dietary shift in the Crested Ibis individuals throughout the experiments.Their consumption of coastal foods increased to 78.47%,while their reliance on loach declined progressively, demonstrating a strong potential for adaptation to local wild food resources. Secondly,the behavioral adaptation of the Crested Ibis individuals followed a sequential process of "observing-probing-ingesting". With the progression of the diet-shifting experiments, the frequencies of probing and ingesting behaviors increased significantly (P < 0.001), reflecting the dynamic process of food-based enrichment driving positive adjustments in behavioral structure. Individual adaptability also varied. Less mobile individuals accepted fewer types of coastal food and took longer to first probe and ingest them than more mobile individuals. 

Conclusion: This study, based on behavioral methodologies, revealed the promotive effect of food enrichment on behavioral diversity from a temporal perspective. The findings indicated that scientifically designed food enrichment training can effectively guide positive adjustments in the behavioral organization of captive animals, thereby increasing the diversity of their natural exploratory and functional foraging behaviors. Based on the results, we recommend establishing a full-cycle "acclimation-release-monitoring" food enrichment management protocol in reintroduction practice. Specifically, this entails pre-release systematic diet-shifting training to broaden the food spectrum of endangered species, the establishment of individual behavioral profiles for quality assessment and precise release planning, and the transitional food supplement feeding based on highly adaptive foods after releasing. This study provides crucial theoretical underpinnings and practical support for optimizing reintroduction protocols for the Crested Ibis and other endangered species.

Key words: Crested Ibis (Nipponia nippon), reintroduction, acclimation, food-based enrichment, behavioral adaptation, coastal wetland