Bare, pale skin occurs
These two tracts, each multifaceted, are narrowly connected, to each side of a large patch of pelage on the chest.
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COMPLEXITY OF PELAGE/BARE SKIN AT ABDOMEN, ELBOW, BUTTOCKS, AND UNDER-TAIL
There is an intriguing aspect of the anatomy of the guanaco, located at the abdomen ('inguinal'), near the elbow ('axillary'), on the buttocks, and on the ventral surface of the tail.
This is
The main function of the pale, apparently bare skin (which also seems to occur on the inner surface of the upper forelegs) seems to be thermoregulation, rather than display by means of colouration.
When the animal stands under normal conditions, the panels of apparently bare skin are 'closed', by virtue of
However, when the slight hunching of the torso is relaxed, what becomes visible is the clear distinction between the ventral pelage and the apparently bare skin,
These apparently bare surfaces presumably function to regulate body heat, via perspiration (https://pubmed.ncbi.nlm.nih.gov/11163922/ and https://www.sciencedirect.com/science/article/abs/pii/S0306456500000140 and https://www.researchgate.net/publication/12165924_Sweating_in_the_guanaco_Lama_guanicoe and https://www.researchgate.net/figure/Scheme-of-a-guanaco-and-the-topographic-areas-where-skin-samples-were-taken1-inner_fig3_231316047) and radiation. In cold weather, the apparently bare panels can be covered, mainly by postural adjustments including the 'clamping' of the tail.
Few ungulates on Earth possess this mechanism, which may be related to the unusually narrow 'waist' of camelids (https://www.inaturalist.org/observations/61249739 and https://www.inaturalist.org/observations/61250535).
At first glance, there is little remarkable about the pale tract on the abdomen in the following (https://www.inaturalist.org/observations/146611617 and https://www.inaturalist.org/observations/123748337).
However, on closer scrutiny it can be seen that there is a considerable area of pale, apparently bare skin. There is another, similar but smaller, patch of pale, apparently bare skin just posterior to the elbow.
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