The puzzle of conspicuous pallor in a Sahelian giraffe, part 2: as opposed to masculine darkness

To understand the pallor in Giraffa camelopardalis peralta (see my last Post), it may also be useful to review the masculine darkness that occurs in most forms of giraffe.

In full maturity, male giraffes become much larger-bodied than adult females: they can weigh up to 1.5 tonnes as opposed to the average 0.8 tonnes of their mothers. They also darken and produce odours from skin glands (https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.2012.00904.x and https://theses.ncl.ac.uk/jspui/handle/10443/1461 and https://www.facebook.com/jumbojunction/photos/a.1554448954625642/6189916674412157/).

Darkness and smelliness are individually variable (https://www.sciencedirect.com/science/article/abs/pii/S0003347219302453). However, the pattern of sexual dimorphism in giraffes is such that males combine:

• indeterminate development (in contrast to the determinate development of females), with
• shorter lifespan than that of females (https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-7998.2012.00904.x).

Estes (1991, page 203) confirms that "Rival bulls recognise and react to one another from a long way off, demonstrating the capability of long-distance communication".

The changes in males at the peak of masculinity detract from their camouflage. However, this poses no particular puzzle, because:

• it is normal for males, particularly in sexually dimorphic species, to trade off security for sexual advantage,
• masculine self-advertisement needs not compromise the camouflage of females and juveniles, because giraffes are only loosely gregarious and dark males tend to be solitary (https://www.sciencedirect.com/science/article/abs/pii/S0003347219302453), and
• males may be less vulnerable than females to predation by day, and dark figures (although conspicuous in bright light) remain inconspicuous by night.

It is noteworthy that the various flags (see https://www.inaturalist.org/journal/milewski/48447-conspicuous-features-of-colouration-in-giraffes#) tend to remain despite the overall darkening in mature males.

Another noteworthy finding is that, in maturing males of Giraffa tippelskirchi tippelskirchi, the whole head remains pale in some individuals (e.g. https://www.istockphoto.com/photo/masai-giraffe-gm1296042780-389584472 and https://www.istockphoto.com/photo/giraffe-in-east-tsavo-park-in-kenya-gm655519816-119240823 and https://stock.adobe.com/sk/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22masai+giraffe%22&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=442967946 https://stock.adobe.com/sk/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22masai+giraffe%22&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=442967951).

The following illustrate various degrees/extents of masculine darkness in various species and subspecies of giraffes:

Giraffa giraffa giraffa

https://www.tripadvisor.in/LocationPhotoDirectLink-g312616-d7122939-i314711382-Moholoholo_Mountain_View_Bush_camp-Hoedspruit_Limpopo_Province.html
http://www.timaverybirding.com/photos/albums/2013/08-09_africa/20130901/safari/giraffe_b.jpg
https://es.123rf.com/photo_21431497_giraffe-bull.html
https://www.facebook.com/mafojanisafaris-100408458676624/photos/pcb.143965800987556/143965734320896/
https://www.africahunting.com/threads/dark-giraffe-bull-hunt-south-africa.55821/
https://www.facebook.com/mafojanisafaris-100408458676624/photos/pcb.143965800987556/143965737654229/
https://www.shutterstock.com/image-photo/big-dark-male-giraffe-swaziland-nature-1719565081
https://www.dreamstime.com/stock-photo-giraffe-browsing-high-leaves-bush-image50867157
https://www.inaturalist.org/observations/25833033
https://www.alamy.com/vertical-portrait-of-a-walking-male-giraffe-with-gymnogene-flying-above-its-head-in-kruger-park-south-africa-image369493417.html
https://www.alamy.com/vertical-portrait-of-lighter-and-darker-giraffe-walking-passed-each-other-in-kruger-park-south-africa-image369044615.html
https://www.inaturalist.org/observations/58934167
https://es.123rf.com/photo_14344382_old-giraffe-standing-next-to-dead-tree.html and https://es.123rf.com/photo_14344348_old-giraffe-standing-next-to-dead-tree.html
https://www.dreamstime.com/male-adult-giraffe-dark-pattern-walking-dry-winter-bush-kruger-south-africa-vertical-portrait-ox-peckers-his-back-image194142317 and https://www.alamy.com/vertical-portrait-of-a-walking-giraffe-with-ox-peckers-on-his-back-in-kruger-park-south-africa-image369083259.html
https://www.inaturalist.org/observations/10160335
https://www.youtube.com/watch?v=5CxgiE512aA

Giraffa giraffa angolensis

https://www.alamy.com/a-large-giraffe-giraffa-camelopardalis-peralta-namibia-image244651145.html
https://www.inaturalist.org/observations/5647366
https://www.inaturalist.org/observations/19426797
https://www.inaturalist.org/observations/56245174

Giraffa tippelskirchi tippelskirchi

https://www.inaturalist.org/observations/44386793
https://www.flickr.com/photos/davidbygott/4037387278
scroll in http://travelwithkally.blogspot.com/2015/10/serengeti-national-park.html
https://www.shutterstock.com/nb/image-photo/masai-giraffe-giraffa-camelopardalis-tippelskirchii-spelled-1669283635
https://www.alamy.com/a-giraffe-family-with-five-members-including-young-calves-standing-on-the-savanna-image360612331.html
https://www.offset.com/photos/giraffe-is-walking-between-the-bush-on-safari-in-kenya-912635
https://www.inaturalist.org/observations/54487214
https://www.inaturalist.org/observations/35913219
https://www.alamy.com/adult-giraffe-grumeti-tanzania-image3531887.html and https://www.alamy.com/adult-giraffe-grumeti-tanzania-image3531361.html
https://www.robertharding.com/preview/832-387758/masai-giraffes-giraffa-camelopardalis-tippelskirchi-animal-pair-mating/

Giraffa tippelskirchi thornicrofti

https://www.livescience.com/19686-aging-male-giraffes-black-spots.html
https://www.dreamstime.com/vast-open-plains-south-luangwa-giraffe-baboon-warthog-zambia-southern-africa-baboons-african-natural-image106164904

Giraffa reticulata
https://www.dreamstime.com/royalty-free-stock-photos-reticulated-giraffe-image26813158
https://www.dreamstime.com/full-body-portrait-reticulated-giraffe-giraffa-camelopardalis-reticulata-walking-northern-kenya-savannah-landscape-africa-image131865776
https://www.dreamstime.com/stock-images-male-reticulated-giraffe-zoo-waiting-food-miami-south-florida-image38695804

Giraffa camelopardalis camelopardalis

https://www.dreamstime.com/reticulated-giraffe-reticulated-giraffe-standing-sun-nice-day-image108993437
https://www.dreamstime.com/stock-photo-giraffes-mysore-zoo-i-clicked-photo-my-visit-baby-giraffe-was-eating-food-box-known-s-unique-image46191110

Giraffa camelopardalis rothschildi

https://www.flickr.com/photos/wildlifepictures/49439204907
https://www.istockphoto.com/photo/female-giraffe-with-a-baby-in-the-savannah-gm669752120-122872959
https://www.alamy.com/stock-photo-mature-male-rothschilds-giraffe-giraffe-camelopardis-rothschildi-at-47964879.html
https://www.sciencephoto.com/media/441396/view/giraffe-in-uganda
https://www.alamy.com/stock-photo-mature-male-rothschilds-giraffe-giraffe-camelopardis-rothschildi-at-47964865.html
https://www.inaturalist.org/observations/38456853
https://www.alamy.com/stock-photo-rothschilds-giraffe-rothschild-giraffe-baringo-giraffe-ugandan-giraffe-47925641.html
https://www.alamy.com/stock-photo-rothschilds-giraffe-rothschild-giraffe-baringo-giraffe-ugandan-giraffe-47925639.html
https://www.alamy.com/stock-photo-rothschilds-giraffe-rothschild-giraffe-baringo-giraffe-ugandan-giraffe-47925649.html
https://www.alamy.com/stock-photo-rothschild-giraffe-giraffa-camelopardalis-rothschildi-herd-walking-125631277.html
https://www.inaturalist.org/observations/190129545

If it is true that masculine darkness is poorly-developed in G. reticulata, this is in line with the observation that this is the species of giraffe possessing the greatest uniformity in various aspects of its colouration.

We need more information for G. c. peralta. The few photos available suggest that the blotches do darken in mature males (see e.g. https://www.inaturalist.org/observations/28558145). However, this is not enough to give the figure a dark aspect overall, because the matrix seems to remain as pale as in females and immature males.

Masculine darkness in giraffes does not necessarily contradict the idea that the conspicuous pallor of G. c. peralta of the Sahel/Sahara represents a basic adaptive shift among giraffes. It is this pallor, rather than masculine darkness, that is an important exception to any generalisation that the colouration of giraffes functions as camouflage.

Posted on 19 November, 2021 05:12 by milewski