Adaptive colouration in the vicuna (Camelidae: Vicugna vicugna)

Please see https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6562099/.

The vicuna (Vicugna vicugna, https://www.shutterstock.com/image-photo/vicuna-arid-landscape-chimborazo-nature-reserve-603780842 and https://www.inaturalist.org/observations/69950772 and https://en.wikipedia.org/wiki/Vicuna and https://animaldiversity.org/accounts/Vicugna_vicugna/) has woolly pelage, adapted to the snow-free cold at high altitudes in the Andean altiplano (https://en.wikipedia.org/wiki/Altiplano).

Please see https://www.nwf.org/Magazines/National-Wildlife/2002/Return-of-the-Golden-Fleece and https://critterfacts.com/vicuna/ and http://elelur.com/mammals/vicuna.html and https://www.bioexpedition.com/vicuna/ and https://www.nationalparks-worldwide.com/sam/peru/national-parks/vicunas/vicunas.html.

Nothing seems previously to have been written about the adaptive colouration of this, the smallest of camelids (https://escholarship.org/content/qt7xs9j2zs/qt7xs9j2zs.pdf).

DIFFERENCE BETWEEN SUBSPECIES:

The vicuna has

The two differ in their patterns of colouration, as follows:

CONCEPTUAL FRAMEWORK:

The vicuna depends on short vegetation, and is diurnal and gregarious (https://www.istockphoto.com/photo/vicuna-gm529652033-54217656?phrase=vicuna%20and%20young%20in%20lauca%20national%20park).

It would, therefore, be unsurprising if - based on the trends seen in comparable deer and bovids - the pelage of the vicugna were to have conspicuous features of pigmentation/depigmentation.

And indeed, the colouration of the vicuna is such that it tends to stand out from its environment. This is by means of large-scale pale features of the pelage.

However:
What is surprising is the position of the most conspicuous feature of the colouration of the northern ssp.
This is located on the front of the figure (Vicugna vicugna mensalis: https://www.alamy.com/vicua-and-the-volcano-misti-reserva-nacional-salinas-y-aguada-blancaper-image357300976.html?imageid=79108214-DCF7-48E4-A45A-28C871E28077&p=16583&pn=1&searchId=29cecb4231d7c99f92316b37750496dd&searchtype=0).

Most comparable deer and bovids emphasise the posterior, not the anterior, of the figure. The northern ssp. of the vicuna instead combines a frontal bleeze, centred on the chest, with otherwise fairly plain colouration in both sexes.

The pattern seen in the northern ssp. of the vicuna thus differs from that in any other ungulate.

FRONTAL BLEEZE:

The frontal bleeze of the northern ssp. of the vicuna (https://www.mediastorehouse.com.au/ardea-wildlife-pets-environment/fg-aj-105-1303400.html) is an adaptively conspicuous feature, consisting of the following elements:

The frontal bleeze is conspicuous

This is true notwithstanding the fact that no part of the pelage of the vicuna is dark enough to provide particular contrast to the pale surfaces.

CALEONIC COLOURATION:

In the southern subspecies of the vicuna, the pale of the ventral surface of the torso has been extended upwards, anterior and posterior to both the shoulders/scapula and the haunch/upper hindleg.

This results in pale pelage extending broadly and diffusely on to

  • the junction of neck and torso,
  • above the elbow,
  • from groin to hips, and
  • on the buttocks.

Please compare the vicugna with a typical example of caleonic colouration, namely Equus khur:
https://stock.adobe.com/images/indian-wild-asses-equus-hemionus-khur-also-known-as-baluchi-wild-ass-in-the-raan-of-kutch-a-saline-desert-in-gujarat-the-last-natural-sanctuary-for-this-sub-species-of-wild-ass/239537503 and https://fineartamerica.com/featured/1-indian-wild-ass-equus-hemionus-khur-pete-oxford.html.

The following illustrate caleonic colouration in the southern subspecies of the vicuna:
https://www.inaturalist.org/observations/121600503 and https://www.inaturalist.org/observations/88307462 and https://www.shutterstock.com/image-photo/vicunas-salar-de-tara-desert-atacama-112162280 and https://www.inaturalist.org/observations/141842864 and https://www.inaturalist.org/observations/141842863 and https://www.inaturalist.org/observations/38702920 and https://www.inaturalist.org/observations/141842865 and https://www.shutterstock.com/image-photo/group-vicunas-99233132 and https://www.shutterstock.com/image-photo/vicuna-vicgna-vicugna-high-altitude-camelid-22334845 and https://www.shutterstock.com/image-photo/portrait-vicuna-vicugna-by-chalviri-lagoon-1999882352 and https://www.inaturalist.org/observations/47665170 and https://www.shutterstock.com/image-photo/vicuna-vicgna-vicugna-high-altitude-camelid-22503727.

Caleonic colouration in the vicuna results in both

  • the de-emphasis of the pale frontal pelage, and
  • the emphasis of the pale tract on the hips (ileum) in particular.

FACIAL FLAG:

The cheeks of the vicuna (https://www.shutterstock.com/image-photo/portrait-vicuna-vicugna-selective-focus-2145439021) are pale/sheeny enough to be noticeable in many views, This is likely to add to the conspicuousness of the figure (https://pavonivaganti.com/en/vicuna-what-it-is/ and https://www.inaturalist.org/observations/43003648), particularly when the head is moved.

The facial flag qualifies as a conspicuous feature, notwithstanding that

  • the head is remarkably small, relative to the proportions seen in comparable deer and bovids,
  • the paleness of the cheeks seems to be owing partly to a sheen effect rather than depigmentation,
  • the neck is so long that it widely separates the cheeks from the pale chest, and
  • there is no contrasting dark on the head, other than the eyes.

The following shows that, in certain illumination, the cheeks are not noticeably pale: https://andrebaertschi.photoshelter.com/image/I0000SbSgFVcjZPU.

The following is a particularly clear illustration of the hypothetical sheen-effect on the cheek in the southern ssp., V. v. vicugna: https://www.inaturalist.org/observations/61325869.

The following are comparable views, lacking the sheen-effect: https://www.inaturalist.org/observations/107312217 and https://www.inaturalist.org/observations/139067636 and https://www.inaturalist.org/observations/66795801 and https://www.inaturalist.org/observations/146260487 and https://www.inaturalist.org/observations/105434200 and https://www.inaturalist.org/observations/140082618 and https://www.inaturalist.org/observations/37686762.

The following show what is probably the true (modest) degree of depigmentation of the cheeks: https://www.inaturalist.org/observations/141842864.

The following seems to show the sheen-effect in partial effect: https://www.inaturalist.org/observations/140837038.

INCONSPICUOUS HINDQUARTERS:

No pattern on the rump/buttocks of the vicuna seems conspicuous enough to qualify as a bleeze or flag.

This holds true for both subspecies:

The relative inconspicuousness of the hindquarters holds, notwithstanding the facts that

The following show the white tail-tip in the two subspecies:

COMPARISON WITH GUANACO:

The guanaco (Lama guanicoe, https://www.inaturalist.org/taxa/42240-Lama-guanicoe) is worth comparing with the vicuna, because

The southern subspecies of the vicuna resembles the guanaco in its colouration, apart from the lack of any dark on tail or face (https://www.inaturalist.org/observations/61325069).

For the two species overall, the main differences are that

WHY DOES THE NORTHERN SUBSPECIES OF THE VICUNA ADVERTISE ITSELF FRONTALLY?

The habitat of the vicuna is relatively free from predators. This is because

  • South America as a whole has relatively few large carnivores,
  • the Andes are relatively remote and quasi-insular, and
  • within the Andes, the vicuna prefers plains offering minimal cover to predators.

This relative freedom from predation is consistent with

Bleezes and flags function as signals to both conspecifics and predators. In most deer and bovids possessing bleezes and flags, two of the functions of these features are to signal that

  • the individual/group has spotted the predator and is alert and ready to flee, and
  • the individual is fit and thus unlikely to be pursued successfully.

Given the communication with predators, it makes sense that most deer or bovids emphasise the hindquarters in their conspicuous displays.

However, in the case of the vicuna, most signalling is instead likely to be intraspecific/social, and free of implications of imminent flight.

Therefore, it may make sense that the main conspicuous feature on the figure is frontal, facilitating communication in contexts other than encounters with predators.

However, this does not explain the lack of the frontal bleeze in the southern subspecies. Do readers have better ideas?

Also see:
https://www.inaturalist.org/journal/milewski/75011-observations-in-inaturalist-remain-insufficient-to-draw-the-border-between-the-two-subspecies-of-the-vicuna#
https://www.inaturalist.org/posts/75256-subtle-and-multifaceted-adaptive-colouration-in-the-largest-wild-ruminant-in-south-america-the-guanaco-lama-guanicoe#
https://www.inaturalist.org/journal/milewski/75397-comments-on-subspeciation-in-the-wild-camelids-of-south-america#

Posted on January 28, 2023 10:11 AM by milewski milewski

Comments

https://pdf.sciencedirectassets.com/778414/1-s2.0-S1751731110X70434/1-s2.0-S1751731109991443/main.pdf?X-Amz-Security-Token=IQoJb3JpZ2luX2VjED0aCXVzLWVhc3QtMSJGMEQCICPHxrR4E4sbez9OLwaS0a1B00%2BihxmU9JNBV5LTsAq1AiAFuELzJzTTf73ENYWpS7egIE9v4YNHJMm%2B%2Be51QRSwcCrVBAi2%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F8BEAUaDDA1OTAwMzU0Njg2NSIMQP0iYELs68E9d6vGKqkESa%2FH5Pp5jSNB6D1IBv3s2AjNvV9L3r4lHVhxmruWYT2L1qxK8M4P9dc899I%2Fnrrp13eKH9dlswtuTfaQOjUScN3AMHVTcnKou326SK1WDbzCzE2Sj3KdyGfU23qBlG6odBAZ2JsEp84ZBjx8CCrXhYTb8nUJq8uxP3%2BmBIKNLxNxl7bOOl9vI0cAimztg1UxowzAt23Cnk8zEzcG95wwK8zfosJ2QILycZ32t1vURDT%2F1NHt0kB3%2BWLUHEnpsAvhI946jQf2aPCWpRXXr2JWqVqv%2BK32NojOOF23P0KsfPC%2FQKvhc%2FyP4K%2FyUzIPF7ScCWtRw3YlV3%2F8cUb6Apxbi6DZ1YzpWuv9QVdAAW1znhKmR2hZdaIOp62jcJ4TH0P8%2FAyJhznrIsN3MqIvUYVcPyJzBTV%2FTs6qePxdBtMASKh8h4mizT6CRs2TARYaugSiZvzWkv0Hwks%2B%2BfUusuK89l7a7rIeNTM58MRUWyGNdKcXgX2BFJ3MhvlJlD1MPYE%2BbDGCG39NITHcSSAsm1772ImgXyljNborMS7v%2F8zTx9wntn4dRH5izjMxx9hU0xanvMbYjAGNDpjd%2F5OiCu5siyZxnIPXRDABwPGzGOOsqsK8reTRkc05t%2BNCJBbqfEFCQCdEKuX2uB1N%2F5ZO6%2FTDTuqkO6lRXfCnhfqfmn%2B9pct9BtTaVkiHmJNvv1tfwR6o6H1C9WrEhZDgBMnddRS8%2Fg9YYKB8%2FggsZzCy4%2BeeBjqqAVxDtH1U3rpiaVg%2FqjwaqNrCK7L3gqs%2BrUEboRVV3dw7vFe9Q0Pe8xl0XMH7u1KbBhUt2k%2FgYYLN3KAU6u9BWDi35hoPJlwtI%2BauvyW6Y5JXgN2FBifHtY%2BFNAdSmO6C%2FLarkCl91%2BZoe9Php6yOvgBitDT00q03N8MOqnXMyLzyIU0U9gU32SduOhgR5ScrtSkjsM75OPdDH%2BzA7X0ZvbcgsS6UH827fPXR&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Date=20230201T061409Z&X-Amz-SignedHeaders=host&X-Amz-Expires=300&X-Amz-Credential=ASIAQ3PHCVTY5XJS4MMW%2F20230201%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Signature=006fa4ef8a772af485012ce2d04e76b9b2bb48ce53e8351d47d63dab71ed99e3&hash=c89c491eb6b746d29459a63a38fb21139a7a73f44701ea9984d6fdd5aa7d82a8&host=68042c943591013ac2b2430a89b270f6af2c76d8dfd086a07176afe7c76c2c61&pii=S1751731109991443&tid=spdf-c7504e30-b7b0-4765-ab20-62fdb694ded2&sid=ef69823c382fd243ad8b53b8124a896e3213gxrqa&type=client&tsoh=d3d3LnNjaWVuY2VkaXJlY3QuY29t&ua=071a5156545b5c015c55&rr=79288b948c8a29c5&cc=au

Posted by milewski about 1 year ago

https://d1wqtxts1xzle7.cloudfront.net/50060150/CondorTrophicEcologyPerrig_et_al.2016-libre.pdf?1478105586=&response-content-disposition=inline%3B+filename%3DPuma_predation_subsidizes_an_obligate_sc.pdf&Expires=1675235736&Signature=SvWKrz~cyJw7PGlJXBXy4K8HGDF1rGnT9e3rl6b81dpMLCx61-puS5oPN5LITKNQwlLk39qFx2WfmXF6dO4KiW4cE3f1XO13MsKNcnuRUX1GAC8~f3sYs6~ClmkWrhBWuu97RUQF7seyt1cW97xqiNiVCDChaL6F9PxmBMRy5y7nO6HT2jIpZWwhYx6xaLEnrsw4oLE8Dtb9auAFAVEo81PYFhE-Z7Q00N2AMA4th5jhI8ckVJLzEvGQ2gPzwxzb1EdcPCuvGXI6ByeFe2Pm5ngYKJhFHnXZDuxu67LiiMfRNJv6Hdj0tul19smmVbys9A4onTL-XnjqMMJSgtskvA_&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA

Posted by milewski about 1 year ago
Posted by milewski about 1 year ago

The following photo would probably not have been taken, were it not for the conspicuousness of the frontal bleeze:

https://www.inaturalist.org/observations/127130261

This is the northern ssp.

Posted by milewski about 1 year ago
Posted by milewski about 1 year ago

The following photo has remarkable, and misleading, perspective:

https://www.inaturalist.org/observations/103989541.

The smaller figures, at first sight, look like infants. In fact, they are adults, located much farther from the photographer than is the main figure.

Something similar applies to https://www.inaturalist.org/observations/62916385.

Posted by milewski about 1 year ago

@milewski
Yes, the odd shaving pattern is strange. It could be that part was too much of a hassle for the people shearing the vicuna hair? Or simply they were lazy in shaving them.

Posted by paradoxornithidae about 1 year ago

The following shows the lack of a frontal bleeze in the southern subspecies, Vicugna vicugna vicugna:

https://www.inaturalist.org/observations/51506422

Posted by milewski about 1 year ago

FURTHER ILLUSTRATION OF THE DIFFERENCES BETWEEN THE TWO SUBSPECIES:

Vicugna vicugna mensalis:
https://www.inaturalist.org/observations/85055969
https://www.inaturalist.org/observations/15178773

Vicugna vicugna vicugna:
https://www.inaturalist.org/observations/141842864

Posted by milewski about 1 year ago

The following shows that the frontal bleeze is absent from infants:

https://www.inaturalist.org/observations/21027076

Posted by milewski about 1 year ago

The following, of Vicugna vicugna vicugna (https://www.shutterstock.com/it/image-photo/guanaco-mountains-215362522), shows that not only do the cheeks gleam, but the pale extends high enough to catch the light on the buttocks, hips, and junction between neck and torso.

Posted by milewski about 1 year ago

ADDITIONAL PHOTOS OF VICUGNA VICUGNA VICUGNA(most of them mislabelled on the Web):

https://www.alamy.com/atacama-wild-mammals-image366636097.html?imageid=4A756BC4-B745-4137-B1DF-8A77300A856D&p=196286&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.alamy.com/a-young-guanaco-lama-guanicoe-high-on-the-altiplano-in-the-atacama-desert-in-northern-chile-south-america-image418024679.html?imageid=93DF67CF-BC9B-4B68-A363-EC488CA84013&p=16440&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.superstock.com/asset/guanaco-lama-guanicoe-nevado-tres-cruces-national-park-region-iii/1566-13572472

https://www.alamy.com/stock-photo-vicua-plateau-lagoons-region-de-antofagasta-chile-78407331.html?imageid=FA375B2D-B093-4832-B0FC-5A08FDD5B084&p=152253&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.alamy.com/stock-image-guanaco-lama-guanicoe-nevado-tres-cruces-national-park-region-iii-168462626.html?imageid=0F416AF1-4199-44B2-8A85-84D196FC9340&p=394751&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.alamy.com/guanaco-grazing-near-socaire-andes-chile-image340919251.html?imageid=70244C77-30E4-47D4-AA1E-462D2828EA60&p=170136&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.alamy.com/stock-photo-wild-vicuas-in-the-puna-de-atacama-3450-m-of-altitude-salta-and-jujuy-74773299.html?imageid=E508953D-7BF9-4493-B051-9F09B54DEB24&p=152253&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.alamy.com/stock-photo-vicunas-in-the-salar-de-tara-desert-atacama-chile-59211119.html?imageid=B75E7922-91E0-4CD7-B131-253010AA582E&p=55487&pn=1&searchId=3df9b8940faa9e595612c3d449dcdc15&searchtype=0

https://www.flickr.com/photos/remataclan/2717652169/

Posted by milewski about 1 year ago

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