4.5 Conservation and management implications
In our study, we found that collective vigilance of two adults varied as a linear function of observer distance, which helps us determining a distance at which cranes change vigilance from synchronized to coordinated behaviour. As vigilance of synchronization usually occurred under lower disturbance or predation risk circumstance as our results and former studies indicated, we named this distance from observer to black-necked cranes the least safe distance. From the function, we quantified the least safe distance for black-necked cranes and most vulnerable group of 2-2 family was c. 100m and 400m respectively. The 100m safe distance for black-necked crane population is very close to the flight initiation distance (FID) of 76m for the bird (our unpublished data). Since cranes benefit from large group sizes (Pays et al., 2007a), 2-2 families actually were the most vulnerable group for black-necked cranes. Then, for the black-necked crane, we suggest to keep at least 400m distance from tourists in order to create the lowest disturbance, which is valuable in conservation and management. Moreover, our study lets us determine the solution in nature.
AUTHOR CONTRIBUTION: D. Kong: Conceptualization, Methodology, Formal analysis, Original draft preparation, Reviewing and Editing. A.P. Møller: Writing, Reviewing and Editing. Y. Zhang: Software, Formal analysis, Writing, Reviewing.
FUNDING: This work was supported by the National Natural Science Foundation of China (Grant number: 31201725, 31760624). The funders had no role in study design, data collection and analysis, preparation of the manuscript, or decision to publish.
DECLARATIONS : All authors declare that they have no competing interests.
DATA AVAILABILITY STATEMENT : All datasets in the present study are available at Dryad doi: 10.5061/dryad.5mkkwh73j.