Differential utilization of surface and arboreal water bodies by birds and mammals in a seasonally dry Neotropical forest in southern Mexico

Water availability significantly influences bird and mammal ecology in
terrestrial ecosystems. However, our understanding of the role of water as
a limiting resource for birds and mammals remains partial because most of
the studies have focused on surface water bodies of desert and semi-desert
ecosystems. This study assessed the use of two types of surface water
bodies (waterholes and epikarst rock pools) and one arboreal (water-filled
tree holes) by birds and mammals in the seasonally dry tropical forests of
the Calakmul Biosphere Reserve in southern Mexico. We deployed camera
traps in 23 waterholes, 22 rock pools, and 19 water-filled tree holes in
this karstic region to record visits by small, medium, and large-bodied
birds and mammals during the dry and rainy seasons. These cameras were set
up to record videos documenting when animals were making use of water for
drinking, bathing, or both. We compared the species diversity and
composition of bird and mammal assemblages using the different types of
water bodies by calculating Hill numbers and conducting non-metric
multidimensional scaling (NMDS), indicator species, and contingency table
analyses. There was a greater species richness of birds and mammals using
surface water bodies than tree holes during both seasons. There were
significant differences in species composition among bird assemblages
using the different water bodies, but dominant species and diversity
remained the same. Terrestrial and larger mammalian species preferentially
used surface water bodies whereas arboreal and scansorial small and medium
mammals were more common in arboreal water bodies. These findings suggest
that differences in water body characteristics might favor segregation in
mammal activity. The different water bodies may act as alternative water
sources for birds and complementary sources for mammals, potentially
favoring species coexistence and increasing community resilience to
environmental variation (e.g., fluctuation in water availability).
Understanding how differences in water bodies favor species coexistence
and community resilience is of great relevance from a basic ecological
perspective but is also crucial for anticipating the effects that the
increased demand for water by humans and climate change can have on
wildlife viability.

水资源可获得性对陆地生态系统中的鸟类与哺乳动物生态学具有显著调控作用。然而，当前学界对水作为鸟类和哺乳动物限制性资源的作用认知仍不全面——绝大多数相关研究均聚焦于荒漠与半荒漠生态系统中的地表水体。本研究针对墨西哥南部卡拉克穆尔生物圈保护区（Calakmul Biosphere Reserve）内的季节性干燥热带森林，评估了鸟类与哺乳动物对三类水体的利用情况：两类地表水体（水坑（waterholes）与岩溶岩池（epikarst rock pools））以及一类树栖水体（积水树洞（water-filled tree holes））。我们在该岩溶区域的23个水坑、22个岩池及19个积水树洞中布设了红外触发相机（camera traps），以记录旱季与雨季期间小型、中型及大型鸟类和哺乳动物的到访活动。相机设置为录制视频，以捕获动物利用水体饮水、洗浴或同时进行两种行为的场景。本研究通过计算希尔数（Hill numbers）、开展非度量多维尺度分析（non-metric multidimensional scaling, NMDS）、指示物种分析及列联表分析，对比了利用不同类型水体的鸟类和哺乳动物群落的物种多样性与组成。研究结果显示，在两个季节中，利用地表水体的鸟类与哺乳动物的物种丰富度均高于利用树洞的类群。不同水体对应的鸟类群落物种组成存在显著差异，但优势物种与物种多样性并未发生改变。陆生及体型较大的哺乳动物优先选择地表水体，而树栖与攀援型的中小型哺乳动物则更常出现在树栖水体中。上述发现表明，水体特征的差异可能会导致哺乳动物的活动出现生态位分化。不同类型的水体可作为鸟类的替代性水源，以及哺乳动物的补充性水源，这或有助于促进物种共存，并提升群落对环境波动（例如水资源可获得性的变化）的恢复力。从基础生态学视角来看，阐明水体差异如何促进物种共存与群落恢复力具有重要学术价值；同时，这对于预判人类用水需求增长及气候变化对野生动物生存造成的影响也至关重要。