| The habitat selection of animals refers to the selection of available habitats.This behavior can take place at landscape level,home range level and microhabitat level.Therefore,the study and analysis of the relationship between animals and habitats at landscape level,home range level and microhabitat level will help to reveal the adaptation strategies of animals to complex environments.Although multi-level analysis methods have been used to assess the relationship between wildlife and habitat in recent years,few studies have considered the effects of multiple spatial and temporal scales simultaneously at the same level,which may lead to false inferences about the "animal and habitat" relationship.Protobothrops mangshanensis is a large venomous snake endemic to China.Its population is rare,geographical distribution is narrow,and it is in a critical state,which needs to be strengthened protection.The study on the habitat selection of this snake at multi-levels and scales will help to explore its habitat preference,reveal its habitat selection mechanism,and promote the scientific protection of this endangered snake.During July 2016 to June 2020,the distribution sites of P.mangshanensis were obtained by transect survey combined with field patrol survey in the nature reserve.The habitat selection mechanism of P.mangshanensis was studied using 3S technology,"using-random" analysis method,random forest model,generalized linear model and generalized linear mixed model at the landscape level(different spatial scales),home range level,micro-habitat level(different seasons).In addition,three adult individuals of P.mangshanensis were tracked and observed from June to September in 2018,and their movement patterns and home range were evaluated.The main results are as follows:(1)According to the tracking observation of the three individuals of P.mangshanensis from June to September in 2018,the minimum movement distance was 219.6 m,and the maximum movement distance of the three snakes was 435.1 m.Based on the movement characteristics of P.mangshanensis,this research selected 5 spatial scales of which 100 m,200 m,300 m,400 m and 500 m to study the habitat selection of this snake at landscape level.When the spatial scale was 100 m and 200 m,the average tree height and the percentage of coniferous forest were the important variables affecting the habitat selection of the snake at landscape level.At 300 m,400 m and 500 m,average tree height and average slope were important variables affecting the habitat selection of the snake at landscape level.In addition,when the spatial scale was 400 m and 500 m,the average altitude was also an important variable affecting the habitat selection of the snake at landscape level.When the spatial scale was 200 m,the average support rate(Akaike Weight)of the important model was the highest,therefore,it was more appropriate to use this spatial scale to study the habitat selection of P.mangshanensis at landscape level.(2)At the landscape level(spatial scale is 200 m),random forest model analysis showed that average tree height,average slope aspect,average slope gradient,average altitude and percentage of coniferous forest were important habitat variables with higher ranking.Generalized linear model analysis showed that average tree height and percentage of coniferous forest were important variables affecting the habitat selection of P.mangshanensis.When average tree height was 12 m,percentage of coniferous forest<27%,18°<average slope gradient<30°,1000 m<average altitude<1300 m,and slope aspect was sunny and semi-sunny,the predicted value of P.mangshanensis was higher(>0.5).(3)Through the tracking of three individuals of P.mangshanensis for nearly four months,the home range of the snake was 3.9±2.3 hm2 calculated by the minimum convex polygon method(Minimum Convex Polygon,MCP).At home range level,random forest model analysis showed that the important predictors of habitat selection of P.mangshanensis were distance from gully,distance from human disturbance,distance from shrub,distance from canopy gap and distance from rubble mound.The generalized linear model analysis showed that distance from gully and canopy gap were the important variables influencing the habitat selection of P.mangshanensis.When the habitat with a distance of<48 m from gully,the distance from canopy gap>52 m,the distance from rubble mound<46 m,the distance from shrub<47 m,and 90 m<the distance from human disturbance<117 m,the predicted value of P.mangshanensis was higher(>0.5).(4)The main factors affecting habitat selection of P.mangshanensis varied with seasons:in spring,the snake preferred to choose habitats with high fallen log cover,shrub cover,herb cover,rock cover,but small canopy cover;in summer,the snake preferred to choose the habitat with high fallen log cover,shrub cover,leaf litter cover,more small trees and less rock cover;in autumn,the occurrence of this snake was related to the high shrub cover,fallen log cover,herb cover,fine woody debris,and more big trees.Season was an important factor affecting the relationship between P.mangshanensis and the microhabitat.For each microhabitat variable,there was a significant difference between the used and random plot in at least one season(P<0.05).(5)At microhabitat level,the microhabitat data of P.mangshanensis in spring,summer and autumn were summarized into a data set,and the results showed that the shrub cover,fallen log cover,rock cover,herb cover,number of big trees,number of small trees and canopy cover were important predictive variables with higher ranking.The generalized linear mixed model analysis showed that the fallen log cover,shrub cover,herb cover,number of big trees,and number of small trees were important variables affecting the microhabitat selection of P.mangshanensis at microhabitat level.When fallen log cover>22%,shrub cover>30%,herb cover>18%,the number of big trees>16,the number of small trees>10,canopy cover<76%or>87%,10%<rock cover<17%,or ock cover>26%,the predicted value of P.mangshanensis was higher(>0.5).This study showed that the relationship between P.mangshanensis and its habitat could be systematically revealed by multi-level and multiscale analysis.At the landscape level,the important factors which affecting the habitat selection of P.mangshanensis changed with the change of the selected spatial scale.When the spatial scale was 200 m,the habitat selection under landscape level of P.mangshanensis was more appropriate.At the home range level,the habitat selection of P.mangshanensis was mainly related to the distance from gully and distance from canopy gap.At the microhabitat level,season was an important factor influencing the habitat selection of the snake,and the relationships between the snake and microhabitat were different in different seasons.According to the results of this study,the following protection recommendations were proposed:(1)At the landscape level,the protection of native broad-leaved forests and scientific management of secondary vegetation should be reinforced;the area of coniferous forest should be controlled for making sure the broken patch mosaics gradually tends to be a continuous whole;scientific selection of artificial breeding sites and field release sites.(2)At the home range level,the flow and natural distribution of the stream should be maintained to grantee the ecological functions of streams;the canopy density should be preserved to make sure the movement efficiency of P.mangshanensis;attentions must be paid on the management and monitoring of the rubble mounds and surrounding habitats.(3)At the microhabitat level,the protection of important microhabitat elements should be strengthened,and the seasonal variation of microhabitat selection by P.mangshanensis should be pay attention to. |
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