Sherlock Holmes said “the little things are infinitely the most important” and that “without data, he could presume nothing”. In this vein, a Chinese-French team has documented the distribution of the Yunnan Snub-Nosed Monkey indices in space and time in the XiangGuQing mountain forest, China, between 2500 and 4130 m of altitude.
By Patrick Giraudoux
Direct observation and sampling of elusive species of conservation concern can be difficult due to technical and ethical reasons. However, censuses can be indirect and based on the observation of activity indices such as faeces, gnawed leaves, etc.
When coupled with non-invasive genetic methods, this approach can provide extremely precise information about individuals, population sizes, movements and diseases. However, the design of optimal sampling is dependent on knowledge about the relationships between the distribution of animal groups and their indices and possible variation in these relationships.
The Yunnan Snub-Nosed Monkey, Rhinopithecus bieti, lives in one of the most extreme environments of any non-human primate. It is found in 15 discrete populations totalling less than 3000 animals, in north-western Yunnan and south-eastern Tibet, between the Jinsha (upper Yangtze) and the Lancang (upper Mekong) rivers, where it inhabits temperate alpine forest ecosystems.
In 2017, a Chinese-French team investigated the distribution of Yunnan Snub-Nosed Monkeys and their indices (faeces, gnawed leaves, broken twigs) in space and time to document those relationships, their research paper was recently published in Mammalia.
For four months, the first author walked more than 80 km of mountain paths in the forest of XiangGuQing – GeHuaQing, Tacheng, China. Based on counts along trails across the range of a wild group of several hundred animals, they have shown that on a large scale (100 km2) indices were spatially distributed as nested clusters, and that monkeys strongly prefer southern slopes and altitudes ranging between 2900-3400m.
Additional transects carried out across the range of a smaller sub-population of about 60 individuals, showed that stays of 2-3 days in an area of a few hectares were sufficient to get a spatially homogenous distribution of faeces. The researchers also determined that weather and interactions with other species can alter index density, e.g. the number of monkey faeces was on average 4.2 times higher in places where domestic pigs were absent (a consequence of pigs feeding on faeces).
These observations highlight the importance of considering spatial and temporal scales when sampling Yunnan Snub-Nosed Monkey indices. They provide a foundation from which to develop molecular ecology methods using indices and to develop methods for elucidating how Yunnan Snub-Nosed Monkeys range over large areas, and how currently isolated populations may reconnect.
To learn more about this research please visit: https://gdri-ehede.univ-fcomte.fr/spip.php?article12.
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