Thermoregulatory panels in the guanaco

Bare, pale skin occurs

• on the ventral surface of the tail, extending via the buttocks to the groin, inner upper hindlegs, belly, and posterior flanks.
• on the brisket, extending to the pits of the forelegs and the inner upper forelegs.

These two tracts, each multifaceted, are narrowly connected, to each side of a large patch of pelage on the chest.

https://www.dreamstime.com/guanako-lying-back-guanako-lying-back-torres-del-paine-national-park-patagonia-chile-image117519668

https://www.dreamstime.com/stock-photography-guanako-wollowing-dust-image16387852

http://images.frankkrahmer.com/media/23e2769e-f544-4547-91d4-c88686dbcad2-guanaco-dust-bathing-lat-lama-guanacoe-south-america-chil

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 sharp differentiation of long pelage from apparently bare skin, and
• the difference between the pale skin of groin, buttocks, and tail and the dark skin of the perineum.

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

• slight hunching of the torso, which keeps the upper hindlegs and elbow close to the torso (https://www.mediastorehouse.com.au/nature-picture-library/2019-december-highlights/rf-guanaco-lama-guanicoe-standing-mountain-19737708.html), and
• relaxation of the tail, which covers the bare skin of both the ventral surface of the tail and the perineal area (https://www.shutterstock.com/it/image-photo/curious-guanaco-lama-guanicoe-endless-grass-1226553520).

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,

• posterior to the belly (https://www.shutterstock.com/it/image-photo/guanako-stands-guard-front-mountains-blue-1459757072 and https://www.shutterstock.com/it/image-photo/guanaco-ischigualasto-nature-park-1226606107 and https://www.inaturalist.org/observations/122312497 and https://www.shutterstock.com/it/image-photo/guanaco-standing-on-top-hill-dark-2101909417 and https://www.inaturalist.org/observations/106039959), and
• posterior to the elbow (https://www.inaturalist.org/observations/66334242 and https://www.inaturalist.org/observations/107250616).

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.

Publicado el junio 11, 2023 05:10 MAÑANA por milewski