Hibernal Habits And Habitat Selection Of Bufo Gargarizans In Badagongshan,Hunan Province

Winter is an important period of the wild animals' life cycle,during which the vegetation and food resources are dramatically reduced.Thus,it results in significant effects on the physiological traits and behaviors of animals.Hibernation,which is one of the numerous adaptions methods evolved by during nature selection,has been considered as the most important way to alive in the extreme environment of winter.However,the characteristics of different hibernacula may vary with their different climatic conditions and provide different resources to the animals.Therefore,hibernal selection is an important component of over-winter strategies and the relative studies could reveal the significance of wild animals' over-winter demands.The Asiatic toad,Bufo gargarizans,is a commonly observed amphibian species with a vast distribution in China.Previous researches were mainly focused on its medicinal values while the ecological research,especially for the traits and data of overwintering ecology is relatively lacking.Our study investigated the overwintering habits,hibernal habitat selection,and habitat factors preferences of B.gargarizans.During October to December of 2015,February to April and October to December of 2016,we conducted transects,sampling plots and local-resident communications to collect data of the overwintering habits and hibernal habitat selection of B.gargarizans in Badagongshan National Nature Reserve,Sangzhi,Hunan Province.The hibernal time,hibernal posture and hibernal characteristics of B.gargarizans were observed and recorded in our field surveys.Within 252 sampling plots,we collected the data of 18 ecological factors for the wintering habitat selection of B.gargarizans,including distance from water source,distance from breeding sites,distance from human activities,land use type,vegetation type,gravel degree,ground condition,the highest height of herbaceous plants,the lowest height of herbaceous plants,soil hardness,depth of leaf litter,depth of humus,canopy cover,slope,aspect,slope position,microhabitat temperature,and microhabitat humidity.According to Akaike Information Criterion(AIC)information theory,we established the best-fit model of hibernal habitat selection by B.gargarizans,and then constructed the logistic regression among B.gargarizans occurance and absence habitat factors.Finally,the Resource Selection Indexs(RSIs)were used to analyze the preferences of habitat factors by the toads.The main results of our study are as follows:(1)The whole hibernation period of B.gargarizans lasts about four months,that is,from the end of October,when daily mean temperature is below 10?,to the end of February the next year,when daily mean temperature is above 5?.There was no significant correlation among depth of hibernal nest,SVL,body weight,and body condition index of B.gargarizans(| r |<0.5,p>0.05).However,a quadratic function relationship(y = 0.356x2-7.305x + 44.589,R2=0.397,p<0.05)was detected between depth of hibernal nest and microhabitat temperature,showing that the toads need to establish deeper hibernal nest under higher or lower microhabitat temperatures.(2)Body condition index(BCI)of B.gargarizans was significantly increased after the hibernation,comparing to the BCI before hibernation(F1,55=39.493,p<0.001).An obvious increase of BCI was also detected between after-hibernation and before-breeding stages(F1,39=9.849,p=0.003).However,a significant decline of BCI was showed after breeding(F1,231=48.763,p<0.001).These variations indicated that the toads may have predation behaviors during hibernation,and the energy used for reproduction the next year might not totally comes from their energy storages before hibernation.(3)The best-fit model of hibernal habitat selection based on the AIC information theory included seven ecological factors,including ground condition,land use type,canopy cover,vegetation type,aspect,gravel degree,and slope(AICw=0.994,AICc=-1469.086).The logistic regression of hibernal habitat selection based on the best-fit model showed that the most important ecological factor for hibernal habitat selection is gravel degree(|B|>1,p<0.01),and the important ecological factors are slope and aspect(|B|>1,p=0.047;p=0.042).(4)In winter,B.gargarizans prefers habitat with canopy cover less than 60%(Ei<0),vegetable patchs(Ei=0.500),vegetation type of shrub+weed(Ei-0.697),south-facing slope(Ei=0.623)and weed habitats(Ei=0.470),avoids primary forests(Ei=-0.104),vegetation type of arbor+indocalamus(Ei=-0.300),arbor+shrub(Ei=-0.200),north-facing slope(Ei=-0.136)and strongly avoids gravel ground(Ei=-1.000).This may be because that lower canopy is beneficial for their predation and weed habitats are beneficial for avoiding predators.In summary,the primary factor that affecting hibernal habitat selection of B.gargarizans is gravel degree of the ground,while they also prefer the secondry is the weed habitat.Our study provides valuable information about the overwintering ecology of B.gargarizans,and also could be useful scientific reference to population management of this toad species.