Preliminary investigation on iodine nutrition in captive giant pandas

Background/ObjectiveThe giant panda belongs to the family Ursidae and, as a species of bear, still retains the simple digestive system of a Carnivoran. However, under the pressure of a specific habitat they had to adapt to a plant mono-diet consisting of bamboo with different species and growth stages around the year. A plant-based diet has relatively low iodine content with risk of iodine deficiency. Furthermore, bamboo contains cyanogenic glycosides releasing cyanide whose detoxification metabolite the thiocyanate acts as antagonist against iodine uptake and storage in the thyroid. To date very little is known about the iodine nutritional status of the giant panda, thus this study was conducted to receive the first information about the iodine nutrition of captive giant panda.Subjects/MethodsHere we investigated the iodine content of bamboo with different plant parts/vegetation stage and species and further compounds of the captive giant panda diet. Next, the urinary iodine (UI) and urinary thiocyanate (UT) levels of infant, sub-adult, adult and geriatric captive giant pandas was measured during the periods when the pandas consume both bamboo leaves- and culm (bamboo leaf-culm stage). Afterwards, the UI of 19 adult giant pandas was measured again for the different iodine intake during bamboo shoot stage. Finally, in this study part also the fecal iodine concentration was analyzed for calculation of total iodine excretion in relation to the iodine intake.ResultsBamboo leaves had the highest iodine content (453 μg/kg dry matter (DM)), followed by the shoots (84 μg/kg DM, p < 0.05), while bamboo culm had the lowest value (12 μg/kg DM, p < 0.05). During bamboo leaf-culm stage, giant pandas of different age groups had different UI and UT levels (p < 0.05). Furthermore, UI and UT were positively correlated among sub-adult, adult and geriatric giant pandas (p < 0.05). In adult giant pandas during bamboo shoot stage, the iodine excretion in feces was not different from that in urine while their total iodine excretion was less than their iodine intake (p < 0.05). Moreover, during bamboo shoot stage, the UI level of adult giant pandas was much lower than noted during bamboo leaf-culm stage (p < 0.05).ConclusionsOur results indicate that UI of captive giant pandas was related to their age as well as to the vegetation stage/part of bamboo they consumed reflecting a different periodic iodine supply. Thiocyanate and fecal excretion should be emphasized when considering the iodine nutrition of giant pandas.     

秦岭大熊猫栖息地巴山木竹生物量

巴山木竹是秦岭大熊猫冬、春季食物的主要来源,其生长状况、数量和空间分布格局与大熊猫的生存与活动有着密切的关系。为了探讨不同立地因子对巴山木竹生物量的影响,确定巴山木竹生长的主导因子和适宜立地条件,在秦岭大熊猫栖息地内选取54块样地,对不同立地条件下巴山木竹生物量进行了测定。通过统计分析,结果表明:由于不同地区气候和土壤条件的差异,导致了巴山木竹生物量亦存在较大差别;巴山木竹生物量在其分布区内随海拔的升高而呈规律性变化,1500—1700 m为最适分布区域,其生物量最大;坡度越大生物量越小,陡坡不适宜竹林的生长;上坡位不利于竹林生长,而中、下坡位生物量没有显著差异;坡向对生物量的影响不明显,均适宜巴山木竹生长;在落叶阔叶和针阔混交林中,当林冠郁闭度>0.6时,竹林生长减弱。在这些立地因子中,影响巴山木竹生物量积累的主导因子是坡位和林冠郁闭度。     

Back-and-forth shifts in habitat selection by giant pandas over the past two decades in the Daxiangling Mountains,southwestern China

Habitat selection is a complex process, and animals may change their habitat selection over time. However, we have a poor understanding of temporal variation in habitat selection of endangered giant pandas (Ailuropoda melanoleuca), which has limited the development of conservation strategies for them. This study examined giant panda habitat selection in three stages of the past two decades (2001–2002, 2011–2012, and 2019–2020) in the Daxiangling Mountains, southwestern China. We applied the resource selection function to estimate the probability of species occurrence with five limiting habitat factors, i.e., elevation, slope, aspect, tree diameter at breast height, and bamboo cover. We found that giant pandas consistently selected for south- and west-facing slopes with mid-elevations and large trees in the three stages. However, there were shifts back-and-forth in the choice between higher and lower elevations and between higher and lower bamboo cover across the three stages. We suggest that the giant panda habitat selection had important consequences for gaining the high availability of palatable bamboo and good shelters. The back-and-forth shifts might be the result of changes in the type, spatial distribution, and intensity of human disturbance. Our study provides insights for improving our understanding and approaches for quantifying temporal variation in habitat selection in giant pandas and other species, suggesting that adaptive conservation and management in response to changing environments is needed.     

Behavioral preferences for bamboo in a pair of captive giant pandas (Ailuropoda melanoleuca)

Giant pandas (Ailuropoda melanoleuca) are members of the order Carnivora. Their diet, however, consists almost entirely of bamboo. Herbivores are under strong pressure to be selective in what they eat because of the low digestibility of plant material. The purpose of this study was to determine whether two captive giant pandas exhibited preferences among three species of bamboo: black (Phyllostachys nigra), bissetii (Phyllostachys bissetii), and arrow (Pseudosasa japonica). Eighteen classic choice trials were conducted in which the species were randomly paired and placed in one of two predetermined locations in the giant pandas' indoor enclosures. The pandas preferred leaves to culms or branches for each bamboo species. In the first hour of exposure, both pandas exhibited a preference for arrow bamboo. A comparison of total bamboo consumption over the course of the night indicated a strong preference for arrow bamboo by the male. The female exhibited equal preference for both arrow and bissetii over black bamboo. Further examination of feeding behavior determined that the pandas processed arrow bamboo behaviorally more efficiently than the other two species. This is the first study to experimentally assess bamboo preferences in giant pandas, and may have implications for husbandry and management programs as well as strategies for in situ conservation. Zoo Biol 24:177–183, 2005. © 2005 Wiley‐Liss, Inc.     

Energy digestibility of giant pandas on bamboo‐only and on supplemented diets

Endangered giant pandas (Ailuropoda melanoleuca) are bears (Family Ursidae), within the order Carnivora. They specialize on an herbivorous diet of bamboo yet retain a gastrointestinal tract typical of their carnivorous ancestry. The evolutionary constraints of their digestive tract result in a low extraction efficiency from bamboo (<40% in reported studies). The goal of this study was to determine the energy digestibility of bamboo by giant pandas used in digestibility trials and through subsequent analyses with bomb calorimetry. Seven digestibility trials were conducted (three with bamboo‐only diets and four with supplemental diets). Energy digestibilities ranged from 7.5–38.9% for mixed diets and 9.2–34.0% for bamboo‐only diets. The bamboo‐only trials summarized here represent, to our knowledge, the first empirical data available for energy digestibility on a bamboo diet for giant pandas. Zoo Biol 30:121–133, 2011. © 2010 Wiley‐Liss, Inc.     

气候变化对邛崃山系大熊猫主食竹和栖息地分布的影响

气候变化对生物多样性的影响,特别是珍稀濒危物种的影响是当前的研究热点。全球气候变化对大熊猫的影响一直受到广泛关注。根据野外调查的大熊猫活动痕迹点、竹类分布点和主食竹扩散距离数据,采用Maxent模型,利用植被、地形、气候等因素,在RCP8.5下分析了2050年和2070年邛崃山系大熊猫主食竹分布及栖息地变化趋势。结果显示:(1)未来大熊猫适宜生境及主食竹气候适宜区面积均有所减少,到2070年分别减少37.2%和4.7%;(2)未来主食竹分布范围总体向高海拔扩展,但面积持续减少,到2070年分布面积比当前减少8.3%;(3)大熊猫栖息地未来有向高海拔扩张的趋势,在低海拔地区退缩明显,到2070年较当前减少27.2%;但到2070年大熊猫栖息地面积加上非栖息地有主食竹分布的面积,较现有大熊猫栖息地面积大1.5%;(4)受气候变化影响较严重的区域是邛崃山系南部以及低海拔地区,其余区域所受影响相对较小;(5)未来需要加强对受气候变化影响严重区域的监测与保护,特别是邛崃山系中部的大熊猫集中分布区。     

Synergistic effects of anthropogenic disturbances on giant pandas

Livestock grazing and the collection of bamboo shoots are the main threats to giant panda (Ailuropoda melanoleuca) habitat in the Liangshan Mountains in China. It is important to clarify the effect of these disturbances to the giant panda to formulate targeted management policies. Based on species distribution models and daily activity models, we investigated the effects of livestock grazing and bamboo shoot collection on giant pandas from May 2021 to July 2022. Our results indicated the giant panda's suitable habitat in the reserve covered 51.83 km² (15.02% of the reserve area). Grazing and bamboo shoot collection led to losses of 19.08 km² and 7.68 km² of suitable habitat, respectively. Together, the 2 activities resulted in a loss of 28.35 km² of suitable habitat, which was more than half of the area of panda habitat. The areas of suitable habitat for giant pandas significantly overlapped with the areas affected by both disturbances. Giant pandas did not show significant differences in daily activity rhythms under a single disturbance, but the daily activity rhythms of giant pandas differed when we compared the area combining the 2 disturbances with the undisturbed area. Our study reveals that the anthropogenic disturbances in the reserve have varying effects on the suitable habitat range and daily activity rhythm of giant pandas and evidence of a synergistic effect. Therefore, when formulating relevant conservation policies, it is important to fully evaluate the extent and characteristics of anthropogenic disturbances in shaping the population distribution and habitat preferences of the giant panda and other wildlife to enhance the efficacy of conservation management practices.     

Seasonal shifts in giant panda feeding behavior: relationships to bamboo plant part consumption

The giant panda (Ailuropoda melanoleuca) is classified as a carnivore, yet subsists on a diet comprised almost exclusively of bamboo. Wild and captive giant pandas use highly selective foraging behaviors for processing and consuming bamboo. These behaviors are for the first time quantified in captive giant pandas over a 5‐year period of time showing highly specific seasonal trends. Giant panda feeding behavior was recorded using live video observations of two giant pandas housed at the Memphis Zoo from November 2003 to June 2008. Leaf was the primary plant part consumed from June to December, whereas culm was consumed primarily from February to May, with both bears displaying similar seasonal shifts in plant part consumption. From May to June, leaf consumption increased significantly (P‐values<0.001); from June to August, leaf consumption remained high and stable. From December to March, leaf consumption decreased significantly (P‐values<0.001). Specific behaviors for bamboo leaf and culm consumption were also observed. Both bears formed wads of leaves before ingestion while feeding on leaf, but the male employed this feeding behavior more often than the female (54 and 33%, respectively). Both bears used similar culm‐stripping behavior (26 and 25%), used to remove the outer layer and isolate the pith for consumption. This study indicates that unique seasonal foraging behaviors observed in wild pandas are also apparent in captive animals in relation to plant part selectivity and feeding behaviors. Zoo Biol 29:470–483, 2010. © 2009 Wiley‐Liss, Inc.     

TAS2R20 variants confer dietary adaptation to high‐quercitrin bamboo leaves in Qinling giant pandas

Sensitivity to bitter tastes provides animals with an important means of interacting with their environment and thus, influences their dietary preferences. Genetic variants encoding functionally distinct receptor types contribute to variation in bitter taste sensitivity. Our previous study showed that two nonsynonymous sites, A52V and Q296H, in the TAS2R20 gene are directionally selected in giant pandas from the Qinling Mountains, which are speculated to be the causative base‐pair changes of Qinling pandas for the higher preference for bamboo leaves in comparison with other pandas. Here, we used functional expression in engineered cells to identify agonists of pTAS2R20 (i.e., giant panda's TAS2R20) and interrogated the differences in perception in the in vitro responses of pTAS2R20 variants to the agonists. Our results show that pTAS2R20 is specifically activated by quercitrin and that pTAS2R20 variants exhibit differences in the sensitivity of their response to the agonist. Compared with pTAS2R20 in pandas from other areas, the receptor variant with A52V and Q296H, which is most commonly found in Qinling pandas, confers a significantly decreased sensitivity to quercitrin. We subsequently quantified the quercitrin content of the leaves of bamboo distributed in the Qinling Mountains, which was found to be significantly higher than that of the leaves of bamboo from panda habitats in other areas. Our results suggest that the decreased sensitivity to quercitrin in Qinling pandas results in higher‐quercitrin‐containing bamboo leaves to be tasting less bitter to them and thus, influences their dietary preference. This study illustrates the genetic adaptation of Qinling pandas to their environments and provides a fine example of the functional effects of directional selection in the giant panda.     

野生大熊猫与放牧家畜的空间利用格局比较

空间利用是野生动物对环境资源的利用模式和活动格局,影响着种群之间的基因交流和生存发展。我们于2010～2012年在四川卧龙国家级自然保护区的“核桃坪”及其附近区域,采用GPS颈圈跟踪技术对分布和放养于该区域的野生大熊猫和放牧家畜—马群进行了定位监测和样地调查。分别选择了3只大熊猫和3个马群的代表性个体的GPS颈圈数据,在地理信息系统（GIS）中通过数字高程模型（DEM）、动物移动模块等工具提取和计算了它们活动区域的地形地势、巢域大小、日移动距离和核域数量,并检验了野生大熊猫和放牧家畜空间利用的差异性。结果表明：野生大熊猫和放牧家畜不同月份和整体之间在海拔高度、坡度坡向、巢域面积、日移动距离和核域数量等方面都具有显著性的差异。野生大熊猫表现为随季节和食物类型（竹笋、竹秆、枝叶）丰度的变化分别活动于拐棍竹林、短锥玉山竹林和冷箭竹林中,活动空间较大（海拔范围、巢域大小）、日移动距离较短和核域数量多等特征的随机扩散模式,且不同个体和月份之间波动性较大;放牧家畜则因初始放养于不同区域的竹林（拐棍竹林、冷箭竹林）和人为干涉程度的大小差异,显示出不同的空间利用格局,但与大熊猫相比,总体而言都具有巢域面积小、日移动距离略大、核域数量极少等“步步为营”空间利用模式的特征,且不同畜群和不同时间之间的变化幅度也小于大熊猫。不同的空间利用格局对环境资源的影响强度截然不同,大熊猫的利用模式有利于竹子资源的更新恢复和生境结构的持续发展,而放牧家畜的利用模式将造成竹子资源的死亡衰败和生境结构的破坏退化。因此,加强放牧家畜的管控,有效协调社区经济发展和生物多样性保护成为卧龙自然保护区（特区）今后工作和管理的当务之急。     

用间接遥感方法探测大熊猫栖息地竹林分布

竹子是野生大熊猫赖以生存的唯一食物。探测大熊猫栖息地内的竹林分布状况,有助于深入了解大熊猫及其栖息地的空间分布格局与特点,并为评估其栖息地适宜性、破碎化程度和生态承载力提供科学依据。由于大熊猫的主食竹大都生长于林下,直接通过遥感影像解译的方法很难实现对其分布密度的探测。以佛坪自然保护区的两大优势竹种——巴山木竹和秦岭箭竹为例,在运用遥感和GIS方法获取空间连续的环境变量时,引入了林上和林下的光照条件,通过分析不同竹种与各环境要素之间的关系,建立竹子密度的预测模型,最后在GIS空间分析技术的支持下实现了对林下竹子密度的绘制。研究结果显示:该方法能够比较准确地预测出林下竹子的分布状态,对两种竹子的密度预测精度均可达到70%以上。     

基于地理加权回归模型探究环境异质性对秦岭大熊猫空间利用的影响

环境异质性对野生动物分布的影响具有明显的空间不均匀性。传统分析中多采用经典线性回归模型来量化野生动物分布与环境变量之间的关系,难以准确反映物种-环境关系的空间异质特征。地理加权回归(GWR)是近年来提出的一种新的空间分析方法,通过将空间结构嵌入线性回归模型中,以此来探测空间关系的非均匀性。以秦岭大熊猫为例,应用GWR模型分析大熊猫空间分布与环境异质性特征之间的潜在关系,并同经典的全局最小二乘回归法(OLS)进行比较。结果表明,GWR模型的AIC、R~2和校正R~2均显著优于OLS模型,GWR模型的局部回归系数估计能够更加深刻地揭示大熊猫空间分布与环境变量间的复杂空间关系,且GWR模型能够为物种的科学保护提供更加有效的理论支撑。因此,GWR模型可为探究物种-环境关系的空间异质特征提供一种新的方法,在物种栖息地选择与利用研究中具有一定的应用前景。     

Microbial Diversity and Evidence of Novel Homoacetogens in the Gut of Both Geriatric and Adult Giant Pandas (Ailuropoda melanoleuca)

Recent studies have described the bacterial community residing in the guts of giant pandas, together with the presence of lignocellulolytic enzymes. However, a more comprehensive understanding of the intestinal microbial composition and its functional capacity in giant pandas remains a major goal. Here, we conducted a comparison of bacterial, fungal and homoacetogenic microbial communities from fecal samples taken from two geriatric and two adult captive giant pandas. 16S rDNA amplicon pyrosequencing revealed that Firmicutes and Proteobacteria are the most abundant microbiota in both geriatric and adult giant pandas. However, members of phylum Actinobacteria found in adult giant pandas were absent in their geriatric counterparts. Similarly, ITS1 amplicon pyrosequencing identified developmental changes in the most abundant fungal classes from Sordariomycetes in adult pandas to Saccharomycetes in geriatric pandas. Geriatric pandas exhibited significantly higher abundance of a potential probiotic fungus (Candida tropicalis) as compared to adult pandas, indicating their importance in the normal digestive physiology of aged pandas. Our study also reported the presence of a lignocellulolytic white-rot fungus, Perenniporia medulla-panis, and the evidence of novel homoacetogens residing in the guts of giant pandas.     

Decreased microbial diversity and <Emphasis Type="Italic">Lactobacillus</Emphasis> group in the intestine of geriatric giant pandas (<Emphasis Type="Italic">Ailuropoda melanoleuca</Emphasis>)

It has been established beyond doubt that giant panda genome lacks lignin-degrading related enzyme, gastrointestinal microbes may play a vital role in digestion of highly fibrous bamboo diet. However, there is not much information available about the intestinal bacteria composition in captive giant pandas with different ages. In this study, we compared the intestinal bacterial community of 12 captive giant pandas from three different age groups (subadults, adults, and geriatrics) through PCR-denaturing gradient gel electrophoresis (DGGE) and real-time PCR analysis. Results indicated that microbial diversity in the intestine of adults was significantly higher than that of the geriatrics (p < 0.05), but not significant compared to the subadults (p > 0.05). The predominant bands in DGGE patterns shared by the twelve pandas were related to Firmicutes and Proteobacteria. Additionally, in comparison to healthy individuals, antibiotic-treated animals showed partial microbial dysbiosis. Real-time PCR analyses confirmed a significantly higher abundance of the Lactobacillus in the fecal microbiota of adults (p < 0.05), while other bacterial groups and species detected did not significantly differ among the three age groups (p > 0.05). This study revealed that captive giant pandas with different ages showed different intestinal bacteria composition.     

Impacts of temperature on giant panda habitat in the north Minshan Mountains

Understanding the impacts of meteorological factors on giant pandas is necessary for future conservation measures in response to global climate change. We integrated temperature data with three main habitat parameters (elevation, vegetation type, and bamboo species) to evaluate the influence of climate change on giant panda habitat in the northern Minshan Mountains using a habitat assessment model. Our study shows that temperature (relative importance = 25.1%) was the second most important variable influencing giant panda habitat excepting the elevation. There was a significant negative correlation between temperature and panda presence (ρ = −0.133, P < 0.05), and the temperature range preferred by giant pandas within the study area was 18–21°C, followed by 15–17°C and 22–24°C. The overall suitability of giant panda habitats will increase by 2.7%, however, it showed a opposite variation patterns between the eastern and northwestern region of the study area. Suitable and subsuitable habitats in the northwestern region of the study area, which is characterized by higher elevation and latitude, will increase by 18007.8 hm² (9.8% habitat suitability), while the eastern region will suffer a decrease of 9543.5 hm² (7.1% habitat suitability). Our results suggest that increasing areas of suitable giant panda habitat will support future giant panda expansion, and food shortage and insufficient living space will not arise as problems in the northwest Minshan Mountains, which means that giant pandas can adapt to climate change, and therefore may be resilient to climate change. Thus, for the safety and survival of giant pandas in the Baishuijiang Reserve, we propose strengthening the giant panda monitoring program in the west and improving the integrity of habitats to promote population dispersal with adjacent populations in the east.     

卧龙自然保护区大熊猫对拐棍竹笋的选择与利用

拐棍竹是卧龙野生大熊猫春季的主要食物。2014-2016年,从设置的3条固定样线中我们发现了当地野生大熊猫有分段取食拐棍竹笋的现象,且没有到放牧活动和人为干扰严重的河谷区域取食竹林内的拐棍竹笋。它们首先在海拔较低( 2 100 m左右)、新笋发育较早且人为干扰不严重的区域觅食,当这些区域的新笋普遍超过2 m高度时会向海拔较高处迁移。大熊猫优先选择有较高比例粗大竹笋的区域作为觅食场所,且当觅食斑块内新笋普遍较小时对粗笋有倾向性选择(P<0.05),但当环境中的新笋质量较好时,选择性有所降低(P>0.05)。大熊猫在新笋质量较好的觅食斑块中取食率较高,在海拔较高处因竹笋的基径较小所以取食率较低(F=20.12, P<0.05)。大熊猫取食新笋所留残桩高度与周边竹笋的高度呈正比(r=0.50, P<0.001)。为保证大熊猫在新笋期的觅食活动免遭干扰,管理者应该在这一时期严格限制大熊猫活动频繁区域的人为干扰。     

The Microbial Community in the Feces of the Giant Panda (<Emphasis Type="Italic">Ailuropoda melanoleuca</Emphasis>) as Determined by PCR-TGGE Profiling and Clone Library Analysis

Despite having a typical carnivorous digestive tract, the giant panda has a diet consisting exclusively of bamboo, a low-efficiency food source. Given this paradox, we sought to investigate if the giant panda digestive tract is inhabited by organisms indicative of high cellulose diet or their gastrointestinal tract anatomy. The diversity and dynamics of the predominant bacteria in the fecal flora of two adult (male and female) and one young (male) giant panda reared in two different zoos over a 2-year period was studied using 16S rDNA-based approaches. The temperature gradient gel electrophoresis (TGGE) profiles of the 16S rDNA V3 region of the three individuals were highly similar. The structure of their fecal flora remained relatively stable over the 2-year period. Both the most predominant band in TGGE patterns shared by the three pandas and the biggest operational taxonomic unit (OTU) in the clone library were phylogenetically related to Escherichia coli. Gram-negative, facultative bacteria constituted almost 60% of the whole community in the clone library. All the OTUs were related to previously described phylotypes known to reside in the intestine or rumen. The results of our study indicate that the predominant bacterial populations in the intestine of the three pandas were markedly different from that of herbivores. The unbalanced intestinal community structure may play a role in the inefficient digestion of bamboo by the giant pandas.     

从野外大熊猫的粪便估计年龄及其种群年龄结构的研究

本文对野外大熊猫粪便中的竹秆咬节及切缘与竹叶残片量度和破碎状况的研究,并以此对已知年龄个体的牙齿切片和齿冠磨损程度进行验证,发现通过粪便分析,可将野外大熊猫种群,大体划分为4个年龄组。     

Evidence for Lignin Oxidation by the Giant Panda Fecal Microbiome

The digestion of lignin and lignin-related phenolic compounds from bamboo by giant pandas has puzzled scientists because of the lack of lignin-degrading genes in the genome of the bamboo-feeding animals. We constructed a 16S rRNA gene library from the microorganisms derived from the giant panda feces to identify the possibility for the presence of potential lignin-degrading bacteria. Phylogenetic analysis showed that the phylotypes of the intestinal bacteria were affiliated with the phyla Proteobacteria (53%) and Firmicutes (47%). Two phylotypes were affiliated with the known lignin-degrading bacterium Pseudomonas putida and the mangrove forest bacteria. To test the hypothesis that microbes in the giant panda gut help degrade lignin, a metagenomic library of the intestinal bacteria was constructed and screened for clones that contained genes encoding laccase, a lignin-degrading related enzyme. A multicopper oxidase gene, designated as lac51, was identified from a metagenomic clone. Sequence analysis and copper content determination indicated that Lac51 is a laccase rather than a metallo-oxidase and may work outside its original host cell because it has a TAT-type signal peptide and a transmembrane segment at its N-terminus. Lac51 oxidizes a variety of lignin-related phenolic compounds, including syringaldazine, 2,6-dimethoxyphenol, ferulic acid, veratryl alcohol, guaiacol, and sinapinic acid at conditions that simulate the physiologic environment in giant panda intestines. Furthermore, in the presence of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), syringic acid, or ferulic acid as mediators, the oxidative ability of Lac51 on lignin was promoted. The absorbance of lignin at 445 nm decreased to 36% for ABTS, 51% for syringic acid, and 51% for ferulic acid after incubation for 10 h. Our findings demonstrate that the intestinal bacteria of giant pandas may facilitate the oxidation of lignin moieties, thereby clarifying the digestion of bamboo lignin by the animal.     

圈养大熊猫野化培训期的生境选择特征

大熊猫(Ailuropoda melanoleuca)是我国特有的珍稀物种,也是世界上最濒危的野生动物之一。为了将人工繁育的部分大熊猫个体重引入其历史分布区或复壮野生种群,中国保护大熊猫研究中心从2003年开始进行圈养大熊猫的野外放归工作,通过野化培训以提高圈养大熊猫适应和选择野外环境的能力。对野化培训大熊猫"淘淘"的生境选择研究表明:该野化培训大熊猫幼仔经常活动于新笋密度较大的区域[生境与对照:(2.68±1.14)对(1.58±0.66)],却避开成竹密度过大[(9.91±2.51)对(12.18±4.68)]、竹子较高[(4.57±1.09) m对(4.98±0.66) m]以及枯死竹过多[(2.52±0.86)对(3.39±1.33)]的区域;喜欢活动于离水源[(1.59±0.67)对(2.19±0.87)]和隐蔽场所较近[(5.37±2.14) m对(8.35±7.76)m],以及距离乔木较远[(3.09±0.69) m对(2.70±0.42) m]和郁闭度较低[(1.85±0.57)对(2.10±0.47)]的区域(P < 0.05),新笋密度大小是该栖息地在整个野化培训期间是否被利用的最重要因素。该野化培训大熊猫幼仔保持着与带仔母兽相近的生境选择特征,对竹子环境的选择也与卧龙野生大熊猫相似,野化培训对该大熊猫幼仔产生了积极的作用。野化培训大熊猫幼仔形成的家域和核域面积分别为9.21 hm² 和1.93 hm²,占野化培训圈面积的51.95%和10.89%,其中家域面积仅有卧龙野生大熊猫的1.4%-2.4%,所以在以后的野化培训过程中需要采取增加野化培训圈中环境丰富度等方式,促进野化培训大熊猫形成较大的家域面积。