Adaptive colouration in the common eland

@davidbygott @tandala @michalsloviak @oviscanadensis_connerties @aguilita @galewski @colin25 @chewitt1 @ludwig_muller

The adaptive colouration of the common eland (Taurotragus oryx, https://www.inaturalist.org/taxa/75192-Tragelaphus-oryx) is, overall, in the category of inconspicuous.

As long as they remain stationary, the animals generally blend into their environment. This is despite their gregariousness and preference for open vegetation (https://depositphotos.com/318325858/stock-photo-herd-of-eland-standing-in.html and https://www.inaturalist.org/observations/104927487).

However, certain features of the colouration are conspicuous, which makes sense for intraspecific communication and group-cohesion. Furthermore, these differ between the two subspecies recognised by Groves and Grubb (2011).

The following show the southern ssp. (T. o. oryx):
https://www.flickr.com/photos/berniedup/46228685341 and https://www.alamy.com/stock-photo-a-pair-of-eland-bulls-in-savanna-in-southern-africa-130628904.html and https://depositphotos.com/242114844/stock-photo-male-eland-antelope-tragelaphus-oryx.html and https://www.alamy.com/stock-image-eland-antelope-in-natural-habitat-168613723.html and https://www.alamy.com/a-herd-of-eland-in-southern-african-savanna-image235462852.html and https://www.dreamstime.com/stock-photos-group-common-elands-taurotragus-oryx-largest-all-antelope-africa-africal-bush-image30145443 and https://www.shutterstock.com/de/image-photo/portrait-large-eland-semi-arid-habitat-1677933370 and https://www.inaturalist.org/observations/117139032.

The following show the northern ssp. (T. o. livingstonii):
https://www.alamy.com/eland-taurotragus-oryx-female-and-calf-masai-mara-national-reserve-kenya-july-image263190299.html and https://prehistoric-earth-a-natural-history.fandom.com/wiki/Common_Eland?file=1a7fc4b7089a77ee51b3f5d2c51fe3a9.jpg and https://www.lakatosafaris.com/the-common-eland/ and https://www.alamy.com/common-eland-image9567218.html and https://www.destinationuganda.com/travel-guide/mammals/common-eland/ and https://www.britannica.com/animal/eland).

At first glance, the main difference between the two subspecies is that the southern ssp. is dull-coloured in the sense that it lacks the stripes (https://www.alamy.com/a-common-eland-adult-female-feeding-on-the-edge-of-scrubland-looking-up-close-side-view-ol-pejeta-conservancy-laikipia-kenya-africa-image245499055.html) that confer an element of disruptive colouration (https://en.wikipedia.org/wiki/Disruptive_coloration) in the northern ssp.

However, closer scrutiny reveals a system of markings better-explained as flags. These advertise the figure once activated by movement.

In the common eland, the flags - which have not previously been documented - are as follows:

  • LARYNGEAL FLAG
  • VENTRAL FLAG
  • ULNAR FLAG
  • CAUDAL FLAG.

The LARYNGEAL FLAG consists of pale on the cheeks and the anterior ventral part of the neck, offset in some cases by dark on the rostrum of the face (https://www.inaturalist.org/observations/75340789 and https://www.shutterstock.com/de/image-photo/group-adult-young-eland-field-yellow-176388800 and https://www.shutterstock.com/de/image-photo/eland-taurotragus-oryx-redbilled-oxpecker-buphagus-1296948118 and https://www.flickr.com/photos/berniedup/50219827822 and https://www.alamy.com/eland-bull-taurotragus-oryx-the-eland-is-the-largest-antelope-in-the-world-measuring-up-to-17-metres-to-the-shoulder-it-inhabits-grass-plains-s-image335481579.html and https://www.shutterstock.com/de/image-photo/two-common-elands-male-walking-on-1654544671 https://www.alamy.com/stock-image-portrait-of-a-large-male-eland-antelope-tragelaphus-oryx-south-africa-163372474.html and https://www.alamy.com/stock-photo-eland-bull-in-bushmans-river-valley-giants-castle-game-reserve-drakensberg-11771441.html).

A feature possibly overlooked in the literature on the common eland is relatively long pelage on the nape and the sides of the neck in mature males (https://www.shutterstock.com/de/image-photo/male-eland-masai-mara-national-park-117718408 and https://www.alamy.com/eland-taurotragus-oryx-male-checking-if-female-is-in-oestrus-masai-mara-national-reserve-kenya-july-image263190298.html and https://www.alamy.com/eland-taurotragus-oryx-male-checking-if-female-is-in-oestrus-masai-mara-national-reserve-kenya-july-image263190298.html). This may offset/accentuate the laryngeal flag. However, it is individually variable (https://www.alamy.com/common-eland-southern-eland-eland-antelope-taurotragus-oryx-the-largest-image66662144.html).

The VENTRAL FLAG consists - depending on subspecies - of either of the following:

The ULNAR FLAG consists of a dark bar on the posterior surface of the foreleg, conspicuous partly because it is offset by pale (https://www.dreamstime.com/common-eland-taurotragus-oryx-southern-eland-eland-antelope-savannah-plains-antelope-east-southern-africa-image115575217 and https://www.alamy.com/stock-photo-common-eland-taurotragus-oryx-antelope-in-a-safari-park-20239318.html and https://www.alamy.com/horizontal-portrait-of-common-eland-taurotragus-oryx-in-grassland-image60488284.html and https://www.alamy.com/elaine-bull-in-kenya-image358852666.html and https://www.alamy.com/common-eland-taurotragus-oryx-lake-nakuru-national-park-kenya-africa-image351773725.html and https://www.alamy.com/safari-in-east-africa-plains-image376898565.html and https://www.alamy.com/stock-photo-common-eland-southern-eland-eland-antelope-taurotragus-oryx-grazing-47822238.html and https://www.alamy.com/stock-photo-common-eland-southern-eland-eland-antelope-taurotragus-oryx-grazing-48764674.html and https://www.alamy.com/a-male-common-eland-taurotragus-oryx-serengeti-national-park-tanzania-image376764151.html and https://www.alamy.com/stock-photo-common-eland-southern-eland-eland-antelope-taurotragus-oryx-grazing-47822243.html),

The CAUDAL FLAG consists of a conspicuously dark tail tassel (https://www.worldinprint.com/common-eland-taurotragus-oryx-red-billed-3626423.html and http://www.shahrogersphotography.com/detail/52087.html and https://www.mindenpictures.com/stock-photo-eland-taurotragus-oryx-sub-adult-male-with-yellow-billed-oxpeckers-naturephotography-image00511848.html and https://www.shutterstock.com/de/image-photo/common-eland-antilope-taurotragus-oryx-bull-1593344851 and https://www.alamy.com/bull-common-eland-taurotragus-oryx-in-high-grass-masai-mara-kenya-image159103761.html and https://www.dreamstime.com/royalty-free-stock-photography-eland-image1456017).

The flags differ between the two subspecies, as follows:

In the southern subspecies, the laryngeal flag is relatively well-developed, and the ventral flag consists mainly of paleness on the legs. The ulnar and caudal flags are relatively poorly developed, as is the dark ventral emphasis ((https://www.alamy.com/stock-photo-common-eland-taurotragus-oryx-adult-female-walking-on-dry-grass-kagalagadi-52204192.html).

Most of the pelage (except e.g. the forehead) of the southern ssp. seems to possess a sheen effect (https://www.inaturalist.org/observations/67701121), not noticeable in the northern ssp. with the possible exception of the junction between cheeks and neck.

In the northern subspecies:

  • the laryngeal flag is relatively poorly developed,
  • the ventral flag consists mainly of the dark ventral emphasis, and
  • the caudal flag is relatively well-developed, because the tail tassel is not only dark but large.

There is a dark tuft on the dewlap. However, this is not large enough to qualify as a flag, and tends to be best-developed in juveniles/adolescents.

Returning to a view of the species as a whole:

The dark face (https://www.alamy.com/eland-cow-pilanesberg-national-park-image465623013.html) differs individually rather than sexually (https://www.alamy.com/eland-taurotragus-oryx-male-checking-if-female-is-in-oestrus-masai-mara-national-reserve-kenya-july-image263190297.html) or between the northern ssp. and the southern ssp.

Dark pelage at the edges of the hooves occurs in the northern ssp. It is retained in at least some individuals of the southern ssp.(https://www.shutterstock.com/de/image-photo/common-eland-antelope-southern-taurotragus-derbianus-1683683407 and https://www.alamy.com/common-eland-antelope-southern-eland-taurotragus-derbianus-or-taurotragus-oryx-image361922237.html and https://www.dreamstime.com/common-eland-taurotragus-oryx-single-mammal-kenya-september-image161969370). However, in neither subspecies is it conspicuous enough to qualify as a pedal flag.

All of the other dark markings - except for the dark rostrum of the face in many individuals - tend to be faded in the southern ssp. (https://www.alamy.com/stock-photo-eland-taurotragus-oryx-in-mashatu-game-reserve-looking-back-botswana-32975319.html and https://www.alamy.com/stock-photo-common-eland-tragelaphus-oryx-mashatu-game-reserve-tuli-block-botswana-31358731.html and https://www.alamy.com/stock-photo-eland-bull-in-an-open-grassland-31789767.html and https://www.krugerpark.co.za/africa_eland.html and https://www.alamy.com/an-eland-antelope-tragelaphus-oryx-in-natural-habitat-south-africa-image416604507.html and https://www.alamy.com/small-herd-of-common-eland-image434799129.html).

The dark bar on the posterior (ulnal) surface of the foreleg is not mentioned in Groves and Grubb (2011). This is a significant omission because

Indeed, the ulnar flag is arguably the single most obvious feature of the northern ssp. (https://www.dreamstime.com/antilope-africa-savanna-wildlife-safari-antelope-savannah-wild-nature-african-game-natural-reserve-image206639055 and https://www.dreamstime.com/antilope-antelope-africa-savannah-wild-nature-african-wildlife-game-safari-natural-reserve-savanna-image206639043 and https://www.dreamstime.com/stock-image-beautiful-giant-eland-antelope-savanna-grassland-largest-entelope-world-image37943041 and https://www.dreamstime.com/royalty-free-stock-images-beautiful-giant-eland-antelope-largest-entelope-world-image37754459 and https://www.dreamstime.com/family-elands-babies-african-savannah-baby-their-mom-standing-maasai-mara-national-reserve-kenya-image166481157).

A audible clicking is produced by mature males in the carpal joint while walking. This raises the intriguing possibility of an anatomical association between this audial signal and the visual signal of the ulnal flag.

However, the flags differ little sexually in the common eland (https://www.inaturalist.org/observations/22603013). Indeed, this species shows limited dimorphism in pelage colouration generally, despite

  • the obvious sexual dimorphism in body mass and shape,
  • the greyness of mature males which results from a thinning of the pelage to expose the dark grey skin beneath, and
  • the development in mature males of a brown tuft on the forehead, extending to between the eyes, that probably produces an olfactory rather than a visual signal of sexual significance.

As males mature and age, the pelage first becomes relatively short and is then lost to thinning (balding) over much of the body, particularly the dewlap (which becomes extremely large in fully mature males). This produces a darkening of the ground colour (https://www.alamy.com/male-pattersons-eland-grazing-with-smile-image445455913.html and https://www.alamy.com/male-pattersons-eland-grazing-with-smile-image445455913.html). However, the paleness of the laryngeal and ventral flags is retained in even in full masculine maturity.

A possible explanation for the subspecific differences:
The environment of the northern ssp. is both more densely vegetated and more perpendicularly illuminated (being tropical) than that of the southern ssp. This may mean a difference in the visibility of certain flags as opposed to others.

Posted on June 10, 2022 04:15 PM by milewski milewski

Comments

https://alchetron.com/Common-eland

Posted by milewski almost 2 years ago

The following shows a buccal semet in the common lend, which I have discussed in a previous Post: https://www.alamy.com/eland-antelope-in-phoenix-zoo-arizona-usa-image340447950.html.

Posted by milewski almost 2 years ago

The following shows the body size of mature males of the common eland, which can reach 700 kg: https://www.alamy.com/eland-bull-killed-in-the-savanna-country-of-rhodesia-zimbabwe-southern-africa-1923-image459061197.html.

Posted by milewski almost 2 years ago

The following shows the colouration on the posterior surface of the ear pinna in Taurotragus derbianus: https://www.alamy.com/stock-photo-eland-54453865.html.

Posted by milewski almost 2 years ago

The following shows that Nanger granti granti has more conspicuous colouration than that of the northern subspecies of the common eland: https://www.alamy.com/stock-photo-herd-of-common-eland-and-grants-gazelles-masai-mara-kenya-49264460.html.

Posted by milewski almost 2 years ago

A tendency to hairlessness is familiar in many megaherbivores, and has been explained by the risk of overheating in massive animals under warm climates. Mature males of the southern ssp. can reach a body mass of >900 kg compared to the mature female body mass of <500 kg.

Because the skin is dark, the partial balding of full maturity tends to result in greying of much of the body, starting on the shoulders and spreading to the growing dewlap and then to the trunk as a whole, though usually not reaching the haunches. Females show this trend to only a limited degree. What has previously been overlooked is that this loss of pelage does not affect the nape and sides of the neck, which retain the youthful pelage even in senility. Because the neck of the mature male bulges muscularly, this cervical fur-patch tends to catch the light.

A difference between the southern ssp. and the northern ssp. is that the cervical fur-patch in mature males is paler in the former than in the latter.

In the southern ssp., it contributes to the laryngeal flag because it extends the pale of the cheeks (where the pelage is short, sheeny, and exempt from the general thinning) on to the neck (https://www.inaturalist.org/observations/67868645).

In the northern ssp., the full expression of this flag is precluded by the cervical fur-patch retaining a dull brown colour rather than appearing bleached, and being too long to show much sheen.

Posted by milewski almost 2 years ago

The following shows that the common eland is less conspicuous than Alcelaphus caama, which possesses a dark/pale bleeze on the hindquarters: https://www.inaturalist.org/observations/90510406.

Posted by milewski almost 2 years ago

The following shows the conspicuously pale legs in the southern ssp.: https://www.inaturalist.org/observations/18478148. These remain in a fully mature male individual: https://www.inaturalist.org/observations/90457762

Posted by milewski almost 2 years ago

The following photos of the newborns and juveniles of Taurotragus oryx livingstonii show that ontogeny plays at best a limited role in the colouration of this species. I conclude that ontogeny. Taurotragus oryx is essentially born with its adult colouration, with the exception of several aspects of the fully mature male. In this way, the common eland is of course similar to other bovid generally and different from cervids. One possible ontogenetic shift is the acquisition of sheen, probably minimally expressed in the infant.
 
One of the clearer differences between the two subspecies is that the northern eland has BOTH the tail-tassel and the dewlap-tuft more conspicuous than in the southern eland. BOTH of these tassels/tufts are larger in the northern form, and darker as well. This is true notwithstanding the fact that in neither subspecies does the dewlap-tuft feature in the mature male. As in all aspects of the colouration of this species, though, there is individual variation.
  
The following shows that, in some individuals, the dewlap-tuft is more conspicuously dark than the mane. This is about as large and dark as the dewlap-tuft gets in the common eland, and as soon as the male starts to mature he loses this feature. This individual has a noticeably dark face but many other individuals do not (in both subspecies).
 
Adult female and neonate:
http://l7.alamy.com/zooms/03d5dc3b816e4c4e8d10d1b38e91b2c4/common-eland-southern-eland-taurotragus-oryx-tragelaphus-oryx-cow-cnygfk.jpg
 
The following greatly exaggerates the hues; no common eland is rufous in nature as seen through human eyes. Please note the precociality of the dark ‘mane’ on the withers, and the presence already in the infant of a small dewlap-tuft even though there is not yet any dewlap. This illumination shows that, in terms of pigmentation (or the lack thereof), any pale flag at junction of cheeks and neck is hardly conspicuous; I infer then that even in the northern eland this pale area is largely created by sheen. This individual does not have a noticeably dark face either. The mane of the adult is not dark (this seems individually variable). I do not think I have ever seen an adult female of T. o. oryx with such a conspicuous dewlap-tuft.
 
Adult female and infant:
http://media.gettyimages.com/photos/common-eland-and-calf-taurotragus-oryx-africa-picture-id176429386
 
The following shows that T. o. livingstonii is no darker at birth than in adulthood. I see few elements of colouration that differ between infancy and adulthood as opposed to masculine maturity. One exception is that the dark hoof-linings seem minimal at birth. Of course, the form of the tail-tassel changes with age. The parsimonious interpretation of the colouration of the infant is camouflage = disruptive colouration.
 
Infants:
http://news.images.itv.com/image/file/27446/image_update_8ac4862fc8b4048d_1336479323_9j-4aaqsk.jpeg 

The following shows the small but significant dark/pale contrast at the apex of the back-of-ear. Although T. oryx acquires a mane already as a juvenile, this is not necessarily dark in the infant (possibly just individual variation).
 
Infant:
http://www.doncasterfreepress.co.uk/webimage/1.5635386.1367419344!/image/337764394.jpg_gen/derivatives/landscape_620/337764394.jpg 

As soon as the horns appear, the hoof-linings seem to appear too (on the other hand, perhaps this is just individual variation).
 
Infant:
 
The following shows that, even in infants, the POSTERIOR surface of the area between hooves and false-hooves is already black. This suggests that the ‘points’ on the northern eland are conspicuous mainly as the animal walks away from the observer – presumably aiding gregariousness.
 
Infants:
http://newsimg.bbc.co.uk/media/images/47560000/jpg/_47560479_it_eland_baby_01.jpg 
 
In the following adult individual, the hoof-linings seem hardly wider than in T. o. oryx, another example of individual variation. Ditto for the fact that this mother’s mane is not dark. The large size and dark tone of the dewlap-tuft is typical of this subspecies.
 
Adult female and infant:
http://www.businessdoncaster.com/wp-content/uploads/2013/05/baby-eland.jpg
 
The following shows the dark mane of the adult and the extremely dark and bush mane and mid-dorsal line of the juvenile. Despite this individual variation, all individuals of T. o. livingstonii seem to have at least part of the line between nape and tail-base noticeably dark, something which cannot be said for the southern eland.
 
Adult female, infant, and juvenile:
https://i.ytimg.com/vi/audNTp4049I/maxresd

Posted by milewski almost 2 years ago

The following is a particularly clear illustration of the conspicuousness of the dewlap-tuft in juvenilesmof the northern ssp.: https://www.alamy.com/stock-photo-eland-taurotragus-oryx-antelope-30934664.html?imageid=F99B5A30-491B-4066-A224-669B82B0CAA3&p=41985&pn=1&searchId=a5c5c645648e91c730635622a834c605&searchtype=0.

Posted by milewski almost 2 years ago

The following nicely shows how large-bodied the northern ssp. of the common eland is, relative to the wildebeest Connochaetes mearnsii: https://www.alamyimages.fr/photo-image-stock-photo-d-un-eland-du-cap-et-des-gnous-stampede-ndutu-tanzanie-fevrier-2009-24962368.html?imageid=E9B9CA90-7C5B-47A9-9F23-EB5A2E6EA595&p=42009&pn=1&searchId=269466ca486da7da0760ab6e735443e0&searchtype=0.

Posted by milewski almost 2 years ago

Nice illustration of anomalous pattern on inner foreleg, linking bushbuck to eland:
 
Tragelaphus sylvaticus mature male:
https://d32f7pyncfosf1.cloudfront.net/2916/shutterstock_246247477.jpg

The above photo might, at first glance, seem to have scant relevance to the common eland.

However, note the surprisingly graphic bar on the inner foreleg, similar in derivation to that seen in:

https://www.istockphoto.com/photo/male-eland-antelope-gm962439908-262854888?irgwc=1&cid=IS&utm_medium=affiliate&utm_source=freejpg_istock_usd.&clickid=xABUceQmnxyOWXNwUx0Mo3kTUkDRBMVxty1qRQ0&utm_term=&utm_campaign=&utm_content=258824&irpid=1328319

https://www.shutterstock.com/image-photo/common-eland-known-southern-antelope-savannah-704337145

Posted by milewski over 1 year ago

Shift
The following is, aesthetically, one of the finest photos I have ever seen of Alcelaphus caama:

https://www.freepik.com/free-photo/beautiful-shot-hartebeests-group-walking-yellow-grass-field_12449256.htm

Posted by milewski over 1 year ago

The following show that the laryngeal flag of Taurotragus oryx can be seen at a distance, in suitable light:

https://www.shutterstock.com/image-photo/panorama-large-herd-eland-buck-standing-176388779

Posted by milewski over 1 year ago

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