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.


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

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 ( and and and 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 ( and

At first glance, there is little remarkable about the pale tract on the abdomen in the following ( and

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.

Posted on June 11, 2023 05:10 AM by milewski milewski


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