| Post-release dispersal of reintroduced animals refers to their temporarily or permanently leaving the release area after being released,including unsuccessful settlement or breeding in the new habitat.To ensure the establishment and persistence of a reintroduced population,the impacts of different factors on the post-release dispersal of captive-bred animals must be assessed.In this paper,we focused on two reintroduced Crested Ibis(Nipponia nippon)populations released in areas located on the southern slope of the Qinling Mountains and the Loess Plateau in Shaanxi Province.Multiple approaches,including post-release monitoring,statistical analysis,and model simulation,were applied to(1)evaluate the survival rate during post-release dispersal and clarify the impact of age,body weight,sex,individual source and release batch on the survival rate of post-release individuals;(2)quantify the dispersal distance and direction of the released individuals;(3)clarify how the pattern of post-release dispersal of Crested Ibis differs between southern and northern areas of Qinling Mountains;(4)model thesuitability of the breeding sites of different populations of Crested Ibis,with reference to the wild population in Yangxian County.The main results are as follows:1.Among the 56 Crested Ibises released in Ningshan,25 individuals survived the first year,corresponding to a survival rate of 44.64%(male 26.79%;female 17.86%)and a mortality rate of 16.07%(male 7.14%;female 8.95%).The survival rate of released individuals was negatively correlated with their age(Spearman,r=-0.344,P=0.03,n=41).The individuals of approximately 3 years of age exhibited a relatively high survival rate in the wild.The post-release survival probability was not significantly correlated with sex,source,body weight,and release order(Spearman,r=0.295,P=0.144;r=-0.69,P=0.738;r=-0.365,P=0.067;r=-0.286,P=0.074;n=41);Among the released ibises in Qianyang County,56.67%survived the first year(male 30%,female 26.67%);and 20%died(male 13.33%;female 6.67%).Moreover,the survival rate of 3-year-old individuals(25%)was much lower than that of other individuals in each age class(?50%).2.Almost all individuals of the two reintroduced populations formed social flocks immediately after release.The post-release dispersal directions of both populations were concentrated.The released ibises in Ningshan County had an average dispersal direction of 210.53°±40.54°(Rayleigh's z Test:z=7.881>z0.05,P<0.01,n=13),and the angular deviation was r=0.779,indicating that the dispersal tended to concentrate in one direction.The ibises preferentially relocated roughly in the southwest direction from the release site where not far from the residences with more paddy fields and more river branches.Both male and female released ibises in Ningshan tended to clump in one direction with an average dispersal direction of 209.78°±38.18°(Rayleigh's z Test:z=4.49>z0.05,P<0.01,r=0.801,n=7)and 211.46°±43.18°(Rayleigh's z Test:z=3.4>z0.05,P<0.01,r=0.753,n=6)respectively.The released ibises in Qianyang County had an average dispersal direction of 27.05°±2.85°(Rayleigh's z Test:z=5.985>z0.05,P<0.01,n=6),and the angular deviation was r=0.999,indicating that the dispersal tended to concentrate in one direction.The ibises preferentially relocated roughly in the northeast direction from the release site,where crested ibises can forage in vast mud flat areas with less residences and woods.3.The average dispersal distance of reintroduced ibises in Ningshan was 5,091.37±4,610.36(n=13)m,in which males dispersed as far as females from the release site to nest sites(males:5,192.48±4,533.37 m,n=7;females:4,973.41±5,130.34 m,n=6;t=0.082,P=0.936);The average dispersal distance of reintroduced ibises in Qianyang was 2,541.42±81.80m(n=6),in which males dispersed not significantly farther than females from the release site to nest sites(males:2,530.39±96.40 m,n=3;females:2,552.46±84.08 m,n=3;t=0.299,P=0.780).4.The average value of the AUC of all three populations in the MaxEnt model was>0.9(Yangxian:0.960±0.042;Ningshan:0.985±0.046;Qianyang:0.995±0.001),indicating that the prediction results were highly accurate and reliable.5.Simulation by a MaxEnt model revealed that the main environmental factors affecting the breeding site selection of wild Crested Ibis in Yangxian County were the distance to water bodies,landscape type,average annual precipitation,and average annual temperature.The breeding site suitability first increased and then decreased with the distance between nest sites and water bodies,reaching a peak when the distance was 25 m.The landscape types that had the greatest impact on the breeding site selection included paddy fields,sparse woodlands,middle-coverage grasslands,and residential area,among which residential area had the greatest impact.The suitability of breeding sites decreased as average annual precipitation increased beyond a certain amount,with the optimal precipitation from 725 to 820 mm.The average annual temperature suitable for the nesting of crested ibis in Yangxian County ranged from 16 to 18?.The main environmental factors affecting the breeding site selection of reintroduced Crested Ibis in Ningshan County were landscape type,average annual precipitation,distance to water bodies,and distance to high-grade roads.The landscape type with the greatest impact on breeding site selection was the paddy field.The suitability of breeding sites decreased as the distance from the nest sites to high-grade roads and water bodies increased,while it increased as the average annual precipitation increased beyond a certain amount,with optimal range from 1,040 to 1,120 mm.In the case of the Qianyang Crested Ibis population,average annual temperature,average annual precipitation,and distance to residence are the main factors affecting the breeding site selection.The breeding site suitability decreased with distance between nest and a residence and increased with the average annual temperature,with most suitable range from 12 to 14?.The breeding site suitability also increased with average annual precipitation,with most suitable range from 780 to 820 mm.6.Among the three populations,there has the highest breeding site suitability in Yangxian County where the sites most suitable to the breeding of crested ibises were concentrated and highly continuous.There were 136.48 km2 of highly suitable breeding areas which accounted for 17.78%of the total area(570.71 km2)of the county.With a patchy and low-continuity distribution,there was an area of 57.38 km2 that was most suitable for breeding which accounted for 13.78%of the total area(506.77 km2)of the Ningshan County.With a concentrated and continuous arrangement,the area of most suitable areas highly affected by climatic conditions was only 5.23 km2 accounting for 7.59%of the total area(75.40 km2)in Qianyang County. |
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