| In winter,sympatric deer species may be subject to constrains from severe environment caused by low temperature and snow cover.Nutritional ecology of sympatric deer concentrates on diet selection and nutritional strategies of target species under their response to changing environment.And all these are of great significance on nutritional differentiation,resource utilization,mechanism of competition and coexistence of sympatric deer species.With support of wildlife field investigation techniques,molecular and nutritional ecology technologies,we studied the food composition and diet selection,foraging strategies at scale of individual plant browse intensity and bite size,nutrition selection and nutrition strategy,as well as habitat suitability of sympatric red and sika deer through the transect survey,from December 2015 to March 2017,in different winter periods in Muling National Nature Reserve of Heilongjiang Province,by snow tracking,surveying bite marks on vegetation,micro-histological analysis and determination of nutritional components of plants.The main results were as follows:(1)Food composition and nutritional niche of sympatric red and sika deer in winter.At the species(genus)level,the proportion and the sequence of forage plant species had significant differences between red and sika deer.The main food of red and sika deer in winter were Euonymus spp.,Acer spp.,Abies spp.and Pinus spp.,accounting for 60-70%of their diets.At forage-category level,For red deer,shrub was the stable and most consumed food items(mean proportions>45%in whole winter),followed by deciduous browse and coniferous browse.For sika deer,deciduous browse(38.53%)and shrubs(33.27%)were the most consumed food items in early winter,while in late winter,the percentage of coniferous browse had doubled significantly from 20.86%to 45.44%,and broad-leaved trees(26.73%)and shrubs(26.57%)account for almost the equal proportion in dietary habits.The food diversity index of red deer in winter was higher than that of sika deer.The dietary overlap index of red deer and sika deer in early winter and late winter was 0.88 and 0.95 respectively,and there was severe competition for food resources between them,which is more intense in the late winter..(2)Winter foraging strategies of sympatric red and sika deer.Both red and sika deer showed strong selectivity for Euonymus spp.,Populus davidiana,and exhibited negative selectivity for Acer barbinerve and Corylus mandshurica.Among the coniferous trees,red deer strongly selected Taxus cuspidate,in contrast,sika deer had positive selectivity for Pinus koraiensis.Browse intensity at the individual plant level and bite diameter were significantly influenced by the winter periods and forage species.Red deer cropped twigs with a mean diameter of 2.70 mm and sika deer cropped twigs with a mean diameter of 2.75 mm.Both red and sika deer took bites with larger diameters from P.davidiana,A.tegmentosum,E.macropterus,and Tilia amurensis,and smaller diameters from C.mandshurica and coniferous browse.In contrast to sika deer,browse intensity on forage species by red deer increased more significantly in late winter,which were represented by A.tegmentosum,E.verrucosus and E.alatus.In contrast to red deer,sika deer significantly increased bite diameter in late winter,which were represented by A.tegmentosum,E.alatus and T.amurensis.Sympatric red and sika deer exhibited different strategies on bite diameter and browse intensity selection in late winter.Red deer may have tended to maintain a higher forage intake through browse intensity variation,whereas sika deer may have tended to fulfill a relatively constant food intake and potential nutritional requirement through bite diameter variation.(3)Food nutrients composition and nutritional strategies of sympatric red and sika deer in winterThe nutrients of plants foraged by red and sika deer varied with plant category and plant species.The crude protein concentration of edible plants in winter were generally lower than the 8%requirement threshold of deer animals.The crude protein content in deciduous trees was lower,while the carbohydrate content was higher.The content of crude protein and crude fat in coniferous trees was higher,but the tannin content was also higher and reached its peak in the late winter.The contents of crude protein,crude fat,carbohydrate and tannin in shrubs were relatively balanced.The average concentration of ADF,cellulose and carbohydrate in the diet of red deer was significantly higher than that of sika deer,and the average concentration of tannin in the diet of sika deer was significantly higher than that of red deer.From early winter to late winter,red and sika deer showed a relatively consistent nutrition selection pattern on the intake of crude protein,crude fat,soluble sugars and carbohydrates.The results of RMT model showed that red deer and sika deer prefered stable intake of crude protein in the face of food nutritional imbalance to ensure their most basic survival needs in winter.At the plant category level,red deer compensate for nutrient imbalance by maintaining stability to shrubs and slightly increasing food intake to coniferous trees.In contrast,sika deer substantially increased coniferous trees and adjusting the intake of shrubs and deciduous trees in late winter in order to maintains a balance of crude protein and other macronutrients.(4)Winter feeding habitat suitability assessment of sympatric red and sika deerRed and sika deer had similar distributions of suitable winter feeding habitats,mainly in the middle and southwest of the reserve.The suitable winter feeding habitat area of red and sika deer were 73.12 km2 and 23.91 km2,which were account for 20.76%and 6.79%of the total area of the reserve,respectively.Niche overlap indices,calculated by ENMTools,showed that two species have general overlap in their ecological niche(D = 0.367,I=0.624).The overlapping feeding habitat comprised 12 km2 of the study area,which contained 16.41%of red deer feeding habitat and 50.19%of sika deer feeding habitat.Human disturbance predictors(distance from farmland,residential area and roads)appeared to be the most influential predictors for sympatric two deer species.The distance to farmland contributed the most to the occurrence probability of red deer,while the distance to roads and settlements contributes the most to the occurrence probability of sika deer.Areas with suitable feeding habitats of the two species of deer are as follows:mixed coniferous and broad-leaved forests that were far from residential areas(4000-6000 m),far from roads(2000 m),far from farmland(2500 m),and low elevation,avoiding pure coniferous forests and pure broad-leaved forests. |
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