育幼洞穴是否构成影响野生大熊猫种群发展的限制因子？—以蜂桶寨自然保护区为例

As a famous flagship species in worldwide wildlife conservation, the giant panda is now confined to six isolated mountains in western China, with a population size estimated about 1600 indiviudals. To keep them sustainable in the wild, knowledge on factors affecitng popluation growth is especially essential when developing adaptive management strategies. .Mammalian cubs' survival is a key population parameter, directly related to their population growth. Besides physiological status, many extrinsic factors can affect cubs' survival, such as maternal care, disease, predators and food availability as well. Of all cutherian mammals, giant panda cubs are the most altricial, with the lowest infant-mother weight ratio. It can be hence expected that their survival are extremely prone to the availability of suitable maternal conditions..Giant panda cubs usually spend 3-5 months in tree or rocky dens after birth. Mother pandas do not stay in one den to rare their cubs during the lactation period, but shift maternal dens frequently, potentially resulting in a higher risk affecting their cubs' survival, such as exposure to predators, and abandonment by mothers when movement. Unfortunately, ecological causes on shifting maternal dens are still less clarified by far..Combined with ecological surveys and noninvasive techniques (auto-triggered infrared cameras, etc.), we will conduct a comprehensive study on reproduction ecology of giant pandas in Fengtongzhai Nature Reserve during 2013-2016. Our goals are: (1) to uncover characteristics in structure， microhabitat and microclimate of maternal tree dens selected by giant pandas, (2) to understand ecological causes resulting in shifting maternal dens, (3) to test Trivers-Willard hypothesis, and (4) to investigate factors affecting cubs' survival during the denning period. Our key scientific question is to clarify whether maternal dens constitute a limiting factor affecting population growth of wild giant pandas in the reserve. .Knowledge accumulated in the research can be not only expected to fill in gaps in the reproduction ecology of wild giant pandas on many aspects, but also highlight some important conservation implications for future management activities, including: .(1) If maternal dens constitute a limiting factor affecting population growth of wild giant pandas, measures including constructing artificial dens can be taken to improve cubs' survival and further promote their population growth; .(2) More and more captive individuals will be reintroduced to reinforce wild isolated small populations in near future. If maternal dens constitute a limiting factor affecting population growth of wild giant pandas, their quantity and quality should be cautiously assessed when selecting a reintroduction area.

大熊猫是我国特有的珍稀濒危物种，种群数量少，生境破碎化严重。尽管当代大熊猫生态学研究已渗透到从分子到景观等不同层次，然而有关影响种群发展的限制因子却基本一无所知。大熊猫初生幼仔发育程度极低，幼仔的顺利存活在很大程度上依赖于适宜育幼洞穴的获得。申请项目在结合传统生态学调查与非损伤性研究手段（如自动感应红外摄像机等）的基础上，就蜂桶寨自然保护区内野生大熊猫繁殖生态学展开广泛、深入的研究，以揭示该地大熊猫育幼树洞的结构、微生境及小气候特征，探讨雌体大熊猫频繁更换育幼洞穴的生态机制，检验Trivers-Willard假说，阐明洞穴生活期影响幼仔存活的生态因素以及适宜繁殖资源（育幼树洞）的存在对种群发展的深远影响。预期研究结果既能填补大熊猫这一珍稀濒危物种繁殖生态学中诸多关键性环节知识的空缺，亦能为采取必要措施（如改善现有洞穴质量、修建人工育幼洞穴等）以促进野生大熊猫种群数量增长奠定理论基础。

项目执行期间，我们对蜂桶寨自然保护区内产仔育幼期间雌体大熊猫洞穴生态学展开了研究，同时结合圈养大熊猫野化放归需要在栗子坪自然保护区开展了系列研究工作，并将研究对象由大熊猫拓展到与其同域分布的其他物种。研究结果表明，蜂桶寨自然保护区内雌体大熊猫对产仔育幼洞穴表现出了明显的选择性，偏好洞穴较小而内洞宽敞的洞穴类型，这些洞穴较为温暖而干燥，往往位于平缓的坡面上，离水源较近且具较好的隐蔽条件，反映了育幼期间保温和安全等方面的需要。研究期间首次获得了野生大熊猫洞穴育幼期间的小气候数据（温度、湿度等）。圈养大熊猫“张想”在适应圈内与野生大熊猫在食性、觅食对策和空间利用上存在明显的差异，表明“张想”在由适应圈进入野外环境后将再次面临环境适应的过程。因此，待放归大熊猫“张想”在适应圈内可能并没有达到适应放归地生态环境条件的目标。森林采伐将导致大熊猫栖息地森林结构的改变及活动痕迹的减少，次生林中大熊猫在觅食对策、空间利用等方面表现出了与原始林中不同的行为模式，因此，尽管天然林禁伐已进行10多年，但森林采伐对大熊猫栖息地及行为的影响依然没有彻底消除。上述研究成果丰富并深化了大熊猫生态生物学知识，对采取人工干预措施提高大熊猫幼仔存活率、实施天然林保护工程及受损大熊猫栖息地恢复等亦具重要的参考价值。在项目资助下，尚揭示了小熊猫发情交配期间7种声音类型的声谱特征及功能意义，填补了小熊猫基础生物学资料的空白。