Which ruminant is born with the most conspicuous facial pattern of colouration? part 1: hippotragin and alcelaphin bovids

@tandala @simontonge @paradoxornithidae @tonyrebelo @jeremygilmore @oviscanadensis_connerties @davidbygott @dejong @michalsloviak @christiaan_viljoen @capracornelius @gigilaidler @maxallen

Various ruminants have bold facial markings in both sexes, helping to make the animals adaptively conspicuous.

An example is https://www.sa-venues.com/wildlife/wildlife_roan_antelope.php.

However, in most ruminants, infants hide for a period (https://www.jstor.org/stable/3061529). This makes it adaptive for the colouration to be inconspicuous at birth.

In this Post, I examine four species of bovids with boldly-marked faces, and I illustrate the colouration in infancy, relative to that in adulthood.

These are

• two hippotragins, in which infants hide, and
• two alcelaphins, in which infants accompany their mothers continually right from the start.

ORYX GAZELLA (https://www.inaturalist.org/taxa/42308-Oryx-gazella)

In this species of hippotragin bovid, adults possess a facial bleeze.

At birth, the facial pattern is not plain. However, it is so nebulous that it is certainly inconspicuous (https://upload.wikimedia.org/wikipedia/commons/0/05/Oryx_gazella_3_-_Gemsbok_cub.JPG).

As infants grow, the facial pattern, like the horns, develops precocially.

https://www.mindenpictures.com/stock-photo-gemsbok-oryx-gazella-female-with-two-calves-namibrand-reserve-namib-naturephotography-image90799302.html

https://www.zoochat.com/community/media/gemsbok-calf-whipsnade-04-jul-2014.262375/

https://www.alamy.com/gemsbok-oryx-gazella-calf-image4734981.html

https://www.alamy.com/gemsbok-oryx-gazella-calf-image4734984.html

HIPPOTRAGUS EQUINUS (https://www.inaturalist.org/taxa/42332-Hippotragus-equinus)

This hippotragin bovid probably qualifies for a facial bleeze in adults (https://www.inaturalist.org/observations/138018015).

The relationship of infants to adults is similar to that in Oryx gazella.

However, the pattern is so precocial that an argument can be made for at least a facial flag in infants. If so, H. equinus may exemplify the presence at birth of a facial flag, in ruminants.

https://www.agefotostock.com/age/en/details-photo/roan-antelope-hippotragus-equinus-calf-standing-in-dry-woodland-fatalah-reserve-senegal-january/FHR-10028-00039-849

https://es.123rf.com/photo_27725369_roan-antelope-hippotragus-equinus-calf.html

https://www.zoochat.com/community/media/roan-antelope-calf.55666/

https://www.zoochat.com/community/media/roan-antelope-calf.145764/

https://www.inaturalist.org/observations/33354786

DAMALISCUS PYGARGUS (https://www.inaturalist.org/taxa/42275-Damaliscus-pygargus)

This species of alcelaphin bovid certainly qualifies for a facial bleeze in adults.

As in the hippotragins shown above, infants are born with a trace of the facial pattern of adults. However, the relative placement of dark/pale is puzzlingly inverted (see https://www.inaturalist.org/journal/milewski/76336-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-2-infants-juveniles-and-adolescents# and https://www.inaturalist.org/journal/milewski/75995-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-2-infants-juveniles-and-adolescents#).

https://www.zooborns.com/zooborns/2012/04/meet-blossom-the-blesbok-calf-born-at-belfast-zoo.html

https://www.dreamstime.com/stock-photos-blesbok-antelope-calf-standing-protectively-next-to-s-baby-image36296983

CONNOCHAETES ALBOJUBATUS (https://www.inaturalist.org/observations?taxon_id=525438)

Unlike the three species shown above, the facial colouration of Connochaetes albojubatus is ambivalent in its boldness. However, I include it here because it is the form of wildebeest with the most conspicuous facial colouration.

In the case of wildebeests, the patterns tend to be obfuscated by

• the confusing complex of species/subspecies, in which various aspects/features of colouration vary in emphasis rather than presence/absence,
• sheen/antisheen and other effects of illumination, and
• individual variation.

However, in adults of C. albojubatus, the cheeks tend to be clearer and paler than in other forms of wildebeest, and equally sheeny. This means that C. albojubatus is the wildebeest most likely to qualify for a facial flag.

What is noteworthy is that the facial pattern is also more preocial in C. albojubatus (https://inaturalist.ca/observations/110949669) than in other wildebeests, with the possible exception of another form with a pale beard, viz. Connochaetes mearnsi.

Adults:

The facial pattern in adults of C. albojubatus is, owing to individual variation and the effects of illumination, not consistent enough to qualify for a bleeze. Its maximum expression is seen in https://www.dreamstime.com/stock-photo-young-male-antelope-wildebeest-standing-marshy-lowland-sunn-sunny-afternoon-image89889139.

This pattern - which does qualify as a facial flag - consists of

• a consistently black rostrum,
• a pale beard, located close enough to the dark muzzle to provide pale/dark contrast, and
• cheeks that are usually pale, sheeny, and free of brindling.

https://www.alamy.com/single-wildebeest-in-amboseli-national-park-image362840009.html

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446124408.html

https://www.alamy.com/stock-photo-eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-57729409.html

https://www.dreamstime.com/blue-wildebeest-wander-grasslands-tsavo-east-park-kenay-image208617369

https://www.alamy.com/blue-wildebeest-connochaetes-taurinus-males-fighting-amboseli-n-p-image443376.html

https://www.dreamstime.com/wildebeest-gnu-portrait-standing-savannah-africa-image155054207

https://inaturalist.ca/observations/5784993

https://www.alamy.com/single-blue-wildebeest-white-bearded-wildebeest-or-brindled-gnu-connochaetes-taurinus-running-across-grassland-of-the-african-savannah-kenya-image240812175.html

https://www.dreamstime.com/wildebeest-gnu-portrait-standing-savannah-africa-image155054207

https://inaturalist.ca/observations/102105372

https://www.dreamstime.com/stock-photos-three-wildebeest-run-image16846173

https://www.dreamstime.com/stock-photo-wildebeest-blue-gnu-connochaetes-taurinus-amboseli-kenya-image67014218

https://www.dreamstime.com/closeup-wildebeest-browsing-closeup-wildebeest-scientific-name-connochaetes-taurinus-nyumbu-swaheli-image-taken-image108980595

https://www.dreamstime.com/royalty-free-stock-photos-wildebeest-connochaetes-taurinus-single-mammal-ground-tanzania-image35926688

https://www.dreamstime.com/royalty-free-stock-photos-wildebeest-image7626258

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446125271.html

https://zooinstitutes.com/animals/eastern-white-bearded-wildebeest-almaty-zoo-26267.html

https://inaturalist.ca/observations/19542826

Infants:

There are too few photos available to assess individual variation. However, the black rostrum tends to be fully expressed at birth.

The cheeks of infants are not as obviously pale as in most adults, and the pale beard (although precocial) is inconspicuous at birth.

However, a previously overlooked aspect is that, unlike adults, the blackish of the face extends ventral to the eyes (https://www.agefotostock.com/age/en/details-photo/wildebeest-calf-in-plains-amboseli-national-park-kenya/AAM-AAES71424). The facial insignia are thus, in a limited sense, better-developed in infants than in adults, making wildebeests unusual among ruminants.

It is noteworthy that Damaliscus pygargus, another alcelaphin, also has a distinction between infants and adults in the colouration of the orbits. The difference is that, in infants of D. pygargus, the orbits are noticeably pale, not noticeably dark (https://www.zooborns.com/zooborns/antelope/).

https://www.dreamstime.com/stock-photo-newborn-wildebeest-amboseli-park-kenya-mother-baby-image76472324

https://www.flickr.com/photos/sdzooglobal/9270596187

Scroll in https://movementoflife.si.edu/species/wildebeest/

https://www.gettyimages.co.uk/detail/news-photo/boston-ma-a-baby-wildebeest-born-in-the-past-week-on-news-photo/1371566822?adppopup=true

https://www.gettyimages.co.uk/detail/news-photo/boston-ma-a-baby-wildebeest-born-in-the-past-week-on-news-photo/1371566810?adppopup=true

https://www.dreamstime.com/stock-photo-newborn-wildebeest-amboseli-park-kenya-mother-baby-rest-herd-background-image76472453

Scroll in https://www.zoonewengland.org/franklin-park-zoo/our-animals/mammals/hoofed/white-bearded-wildebeest/

https://inaturalist.ca/observations/106811995

https://www.jhpostcards.com/products/white-bearded-wildebeest-riga-zoo-animals-1980-latvia-ussr-unused

Juveniles:

The facial pattern in juveniles of C. albojubatus is as conspicuous as that in adults (https://www.dreamstime.com/stock-photo-big-wildebeest-migration-african-safari-amboseli-national-park-kenia-image84361100).

As growth proceeds, the pelage below the eye loses its black pigmentation (https://inaturalist.ca/observations/6812082).

https://www.alamy.com/stock-photo-part-of-a-herd-of-blue-wildebeest-connochaetes-taurinus-grazing-126164867.html

https://www.alamy.com/herd-of-common-wildebeests-walking-in-dry-grassland-on-summer-day-in-amboseli-national-park-kenya-image502860670.html

https://www.alamy.com/blue-wildebeest-connochaetes-taurinus-amboseli-national-park-kenya-image62676645.html

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446124965.html

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446125038.html

https://www.alamy.com/wildebeest-in-the-national-park-tsavo-east-tsavo-west-and-amboseli-in-kenya-image483241293.html?imageid=FE32865D-C28D-4A48-A37B-54D64A5294CF&p=774865&pn=1&searchId=1ded7a829c6fd29f9a553cf0e1e2072e&searchtype=0

DISCUSSION

I know of no ruminant that is born with a facial bleeze.

A facial flag at birth seems plausible in Hippotragus equinus. This would be consistent with

• the extreme colouration of this species, in combining a bold facial pattern with plain colouration over the rest of the figure (https://www.inaturalist.org/observations/142404442), and
• the extremely large size of the ear pinnae at birth (https://es.123rf.com/photo_27725391_roan-antelope-hippotragus-equinus-calf.html).

Since infants of H. equinus hide initially, it is unknown how the precociality of the facial pattern is adaptive. Even in adults, the adaptive value of bold facial colouration in hippotragins remains poorly understood.

What is more complex, and even more intriguing, is the ontogeny of the facial pattern in certain alcelaphins.

The facial pattern in infants of wildebeests ranges from inconspicuous in Connochaetes gnou (https://www.zooborns.com/zooborns/wildebeest/ and https://www.irishnews.com/magazine/daily/2019/08/27/news/rare-baby-wildebeest-born-at-newquay-zoo-1696156/ and scroll to fifth photo in https://africafreak.com/black-wildebeest) to conspicuous in C. albojubatus.

The remaining forms are intermediate, with Connochaetes mearnsi and Connochaetes taurinus mattosi (https://www.dreamstime.com/stock-photo-blue-wildebeest-side-view-mosi-oa-tunya-nation-park-zambia-africa-image61435936) apparently exceeding Connochaetes taurinus taurinus, C. t. cooksoni, and C. t. johnstoni.

For infants of wildebeests to have conspicuous colouration seems consistent with extreme adaptation for gregariousness in open environments, and extreme precociality at birth.

However, it remains unexplained why wildebeests vary in this respect.

It remains possible that C. mearnsi (see first comment below) exceeds C. albojubatus in the consistent boldness of the facial pattern in infants. This depends on further photographic evidence.

Given that, in adults, the facial pattern in C. mearnsi is less conspicuous than that in C. albojubatus, this might make C. mearnsi unique among ruminants, in having a facial pattern more conspicuous at birth than in adulthood.

In this context, I remind readers that infants of wildebeests also possess a pedal flag (https://www.dreamstime.com/stock-photo-blue-wildebeest-connochaetes-taurinus-young-calf-playing-rain-kruger-national-park-south-africa-image60301989), absent in adults.

Publicado el marzo 13, 2023 09:23 TARDE por milewski