The Ecology And Behavior Traits Of Hainan Black-crested Gibbon (Nomascus Hainanus)

Hainan gibbon is the most endangered primates' species in the world now.Because the disturbance of human beings decades,the population of Hainan gibbon declined rapidly,meanwhile,the habitat shrinking continued.As so far,there was a few ecological information or data we knew.During the past four decades,only a few studies on this endangered species were conducted.We conducted the field research on this endangered species in Bawangling National Nature Reserve from August 2002 to September 2007,collected the basic ecological data of this species,such as:the taxonomy,population dynamic,food composition,the vegetation structure of habitat, and how this species selected and used the habitat,reproduction behavior,the relationship between the inter-group encounters of gibbon and the relationship between the gibbon and the other sympatric species.We hope can learn the comprehensive ecological information and provide the scientific suggestions and practice on the surviving of this endangered species.The main results were as followings:1.The taxonomy of Hainan gibbon:The taxonomic status of two crested gibbon taxa - Nomascus sp.cf.nasutus hainanus from Hainan Island,China and Nomascus sp. cf.nasutus from northeast Vietnam is clarified by compared the vocal behavior and the morphology of the two gibbons.The Hainan gibbon,also distributed to east of the Red River,was historically assigned to one species,N.concolor,and have only recently been recognized as one subspecies of the Eastern black crested gibbon N.sp. cf.nasutus.The study,based on their vocal and pelage differences,and the molecular evidence additional,shows that they are distinctive,and herein revalidate the Hainan endemic taxa as Nomascus hainanus and independent species,and deserve the most urgent conservation efforts.2.The historical changes on Halnan gibbon:Census data show that populations of the species used to occur across the whole island,but in 2008 only 20 individuals could be found,confined to a small region,the Bawangling Natural Reserve(19°02′-19°08′N and 109°02′-109°13′E),in the western part of the island,covering only 14-16 km~2.In other words,about 99%of the habitat has vanished in the past 300 years.Such dramatic change has pushed the species to the edge of extinction;Total 20 individuals included only 2 groups and 5 solitary adult males,remained in 2008.The dramatic decline in the gibbon population has occurred due to vegetation reduction, ecological deterioration and extensive human impact.The forest cover was reduced from 95.5%2000 years ago to just 4%in 1999;and the human population in 2003 was 330%larger than in 1950.3.The population character of Hainan gibbon in Bawangling National Nature Reserve:The population of Hainan gibbon which distributed in Bawangling area was same as the other distributed areas in Hainan Island,also experienced the rapid decline at the same time.According the filed study,there are 20 individuals lived in Bawangling now,but the population restoration speed is very slowly,and the saddest thing is no new family group had been set up for a decade years.There are 5 solitary gibbons also lived in Bawangling,the composition is 3 adult males and 2 adult females.4.The vegetation structure of the habitat of Hainan gibbon:The vegetation was the tropical monsoon defoliation forest,and showed the vertical zonal distribution.The vegetation structure selected by Hainan gibbon belonged to mountainous ever green forest,and there were dominant species group among the vegetation composition, which could be divided into five plant formation.It showed that the highest biodiversity index is in the valley of 900-1000 m;meanwhile,there were the most principle component of plant species were eaten by Hainan gibbons.5.The food composition of Hainan gibbon:The total plants species are 122 species,72 genus and 49 families which eaten by the Hainan gibbons,there were 83 species 53 genus and 36 families belong to the rain season foods of Hainan gibbons, the ratio of arbors is 83.1%,the vines are 15.7%and the herbs are 1.2%.The percentage of fruits is from 90.4%to 91.6%,and the young leaves are from 7.2%to 8.4%,the flowers are 1.2%.There are great differences of the food compositions among the Hainan gibbon and the other gibbon species,especially for the ficus fruit. The mainly plant families are Moraceae,Myrtaceae,Annonaceae,Lauraceae, Euphorblaceae,Elaeocarpaceae and so on,which eaten by Hainan gibbon.There were 64 species 31 families plants were recorded,which were eaten by Hainan black-crested gibbon(N.hainanus) in dry season.The life form of the food plants could be divided into arbor(79.7%),vine(15.6%) and herb(4.7%),the components of the dry season were fruits(77.9-82.8%),young leave(17.6-18.8%) and flowers (4.4-4.7%). 6.The selective and utilize on habitat of Hainan gibbon:Hainan gibbon utilized the middle and low area is more suitable habitat for this species,they just utilized the 800-1000 m channels frequently in their current habitat,where diversity and density of fruiting trees is greatest.They did not show the selective on the slope direction and the gradient,and the lowland forests may be the suitable habitat.The home range area of Hainan gibbon is very bigger than the other gibbon species,group A was estimated to be 978 ha,group B was estimated to be 584 ha,this related with the food resource distributed in the habitat unevenly.The ranging distance of Hainan gibbon had a obvious difference between the wet and dry season,the distance in dry season was longer than the wet season's,this may be explained by Hainan gibbon was depend on the fruit as their main food,the observation also testified this point.It showed Hainan gibbon also likes select the higher arbor as their rest and move location.7.The reproductive behavior of Hainan gibbon:Receptive females initiated courtship displays.Copulatory pattems involved the male mounting dorso-ventrally from above and behind.Multiple intromissions with thrusting were brief,lasting＜10 s per copulation.We also observed post-conception proceptivity and copulations in sexually active females.It estimated the gestation period to be 173 d at least.Infants became independent at 1.5 year.The inter-birth interval is ca.24 too.It also suggested that mating activities peak in the rainy season.The Hainan gibbons are polygynous, with a 1 male-2 females mating system.8.Responses to inter-group encounters of the Hainan Gibbon:It showed there were two kinds behavior occurred the encounters between the inter-groups of Hainan gibbon,vocal encounters and agonistic encounters happened between adult females, male sub-adults and male juveniles.The behavior of inter-group encounters of Hainan gibbons were not same as the other gibbon species,no fighting among Hainan gibbon, and not such behaviors as play and grooming,even the extra-group-copulations, meanwhile,the encounters time was shorter than other gibbon species.It suggested the behavior of the adult males was for the sake of protecting their territoriality,and by the way of chasing among under age individuals could make then learn how to protect their future territoriality.9.Responses to inter-species encounters of the Hainan Gibbon:It showed that there were different responses among the human and nonhuman predators' and competitors' encounters of Hainan gibbon.The Hainan gibbons showed the discrepancy responses with the times increasing and the different distances between the human,meanwhile,the reactions of the adult females were different under the condition whether they had baby or not and the aging of the baby.When they met human beings,the adults selected to escape,but the juvenile would like to attack the snake or play with this animal.Hainan gibbons usually drive the other competitor species off the same food resource,but the juveniles did this frequently,just like the squirrel.In general,the adult male of the family was the protector of the group members and the food resource.10.The vocal behaviors of Hainan gibbons:The vocal behavior of Hainan gibbon was different with all the known gibbon species,and it was the simplest song among the Hylobatidae,so this species maybe the original taxon among the gibbons.The vocal behaviors can be divided into five types according to the ecological meanings:1) the territory advertisement duet,2) the summon call,3) the adult male or female's solo call,4) the forewarn call,5) the alarming call.Hainan gibbon is the most endangered independent primate species in the world. The study is the first time to use the GIS technology on the primates' habitat study, and found the gibbon utilizes the resource repeatedly.We found the reduction of habitat and the hunting was the main endangered factors,which shows it is the most important that restores and improves the current habitat for Hainan gibbons.