Adaptive colouration in the black-backed jackal, Lupulella mesomelas

(writing in progress) 

The black-backed jackal (Lupulella mesomelas, https://www.inaturalist.org/taxa/1210966-Lupulella-mesomelas) is surprisingly different from other jackals.
 
The most important aspect of the colouration of L. mesomelas, in functional terms, is that it has a conspicuous feature, making the whole animal stand out from its background: the flank-band.

All other spp. of jackals are coloured to blend into their background.

The following (http://image1.masterfile.com/getImage/NzAwLTAwMTY5MjYzZW4uMDAwMDAwMDA=AHygCA/700-00169263en_Masterfile.jpg) is an excellent illustration of conspicuousness in L. mesomelas, even where the dark, bushy tail obscured
 
 The following (https://depositphotos.com/335946586/stock-photo-jackal-on-the-dry-plains.html and https://www.inaturalist.org/observations/122211981) further show how the flank-band of L. mesomelas makes it more, not less, conspicuous in its typically open habitat. The fact that this is the most diurnal of all jackals helps to make this adaptive conspicuousness understandable.

When an animal is bound to be noticed by its movement in the open in bright light, it makes sense to abandon any attempt to hide, and instead to capitalise on, and accentuate, conspicuousness for social purposes and, in extreme cases, as part of some sort of ‘mind-game’ with predators.

Because all jackals are unusually intelligent for non-primate terrestrial mammals, we can expect that L. mesomelas is playing some sort of ‘mind-game’ with us, not so?

The following (https://thumbs.dreamstime.com/x/black-backed-jackal-juvenile-22118282.jpg) again shows how conspicuous L. mesomelas tends to be. Indeed, no good photographer would even have bothered to push the shutter at this distance, were it not for the fact that this animal stands out so well.

If this was Canis latrans or C. aureus, one would not see a photo taken at this distance because it would not be worth looking at.

Note that the main two elements in the conspicuousness of C. mesomelas are

• the flank-band, and
• the dark tail.

Something that I do not think has ever been pointed out before is that the flank-banding of L. mesomelas is conspicuous even when the animal is facing, or facing away from, the observer (http://l450v.alamy.com/450v/f2e4xe/black-backed-jackal-canis-lupus-in-the-wild-in-cape-cross-namibia-f2e4xe.jpg).

This is because, unlike ungulates, it has relatively narrow hips and shoulders. The individual in the following photo shows additional tonal contrast about the base of the tail, but I do not regard this as typical of this species.

Note that the flank-banding is conspicuous not only because the main band is so dark, but also because it is juxtaposed with particularly pale bands: the pale fawn of the adjacent flank, which is actually paler than the fawn of shoulders and haunches, and the pale grey of the adjacent ‘saddle’.

A feature of the colouration of L. mesomelas which is most significant, but could easily be overlooked in an ‘objective’ description by a taxonomist, is the paleness of the fawn on the upper flank just ventral to the dark band.

I have never seen an argument that this banding is part of some sort of camouflage. Furthermore, I doubt that anyone could make such an argument in any coherent way; i.e. I think we can discount the possibility that there is anything camouflaged about this species.

Camouflage makes little sense in any context or from any perspective in L. mesomelas, and so we have to think why this species would want to go the other way, towards self-advertisement.

The following (https://thumb9.shutterstock.com/display_pic_with_logo/1084712/157839602/stock-photo-black-backed-jackal-late-evening-in-the-savannah-of-masai-mara-kenya-157839602.jpg and https://thumb7.shutterstock.com/display_pic_with_logo/1084712/157842791/stock-photo-black-backed-jackel-masai-mara-kenya-157842791.jpg), of a single individual, nicely show that the flank-banding remains conspicuous even when the flank is not directly presented. The hips and shoulders, being narrow, to not obscure the flanks.
 
The following (https://s-media-cache-ak0.pinimg.com/236x/9c/3c/ca/9c3cca78d14a4c4890c9cb60d789c3c1.jpg and https://twitter.com/WildWingsSafari/status/1525386202697932800/photo/4) again show how the animal remains conspicuous, by virtue of its flank-band, even when viewed, head-on. This is partly the result of the precise configuration and location of the band, which remains visible when the figure is viewed from the front.
 
The following (http://www.wilkinsonsworld.com/wp-content/gallery/miscellaneous-2012/041-black-backed-jackal-1-piper-pan-20042009.jpg) shows not only this conspicuousness of the flank-band, but also the countershading typical of L. mesomelas.

It is, at first, puzzling that an animal should feature both a conspicuous marking, such as a bold flank-band, and countershading, the function of which is usually crypsis because it tends to cancel out the darkness of shadows on ventral surfaces of the neck and body. Any good explanation of the adaptive value of colouration in C. mesomelas must resolve this apparent contradiction, not so?
 
The following several photos inadvertently illustrate some of the analogies between C. mesomelas and a gazelle-like antelope in colouration. This is just the kind of thing that wildlife photographers should seek to portray, but of course these images were taken just by chance because unfortunately I know of no photographer who brings these sorts of concepts to his photography of African wildlife.

https://www.alamy.com/namibia-kunene-region-etosha-national-park-black-backed-jackal-canis-mesomelas-at-nebrowni-pumped-waterhole-image471978616.html
 
https://www.mindenpictures.com/stock-photo-black-backed-jackal-canis-mesomelas-and-springbok-antidorcas-naturephotography-image00548800.html

https://www.robertharding.com/preview/832-396314/blackbacked-jackal-canis-mesomelas-between-springbok-antidorcas-marsupialis/

https://www.dreamstime.com/stock-photo-black-backed-jackal-ront-springbock-herd-etosha-nationalpark-namibia-front-canis-mesomelas-image98617938

https://www.istockphoto.com/photo/black-backed-jackal-and-springbok-at-ozonjuitji-mbari-waterhole-of-etosha-national-gm1405618565-457464928

https://www.istockphoto.com/photo/black-backed-jackal-at-etosha-national-park-in-kunene-region-namibia-gm1405618612-457464912

https://www.istockphoto.com/photo/black-backed-jackal-at-etosha-national-park-in-kunene-region-namibia-gm1405618612-457464912?phrase=dung%20antelope%20nature%20environment

The following (https://rangerdiaries.com/wp-content/uploads/images/diaries/HUdfTWe.jpg) nicely shows the similar, and evolutionarily parallel, effects of flank-banding in C. mesomelas and Antidorcas. The two coexisting mammals are conspicuous for much the same reasons, a major difference being that in the carnivore the tail is also conspicuously dark.
 
The following (http://l450s.alamy.com/450s/b3cxr1/africa-botswana-black-backed-jackal-canis-mesomelas-and-springbok-b3cxr1.jpg) shows the same juxtaposition. An interesting point to note is that, although the upper flank of C. mesomelas is fawn instead of the white seen in the springbok, a similar degree of tonal contrast is achieved because the flank-band in the jackal is actually black, rather than the darkish brown seen in the antelope.

In both cases, the pale tone just ventral to the dark flank-band is high enough on the flank to catch the light most of the time, by day. I wish more photos like this were taken intentionally.

The following (https://photos.smugmug.com/Nature-Animals/Botswana-2015/i-RkrgPm8/1/S/20150703_07-50-39-S.jpg) again shows the same juxtaposition, this time with Antidorcas hofmeyri.

While no member of the Carnivora is coloured like any gazelle, the overall effect is similar and this is what I mean by it being impossible to achieve complete objectivity in one’s descriptions of animal colouration; one always has some assumptions about meaning in the back of one’s mind and the question is to bring these assumptions to consciousness and to make them as relevant as possible.

The following (https://www.alamy.com/jackal-and-springbok-at-okaukuejo-waterhole-etosha-national-park-namibia-image345398256.html) again shows the same juxtaposition.

The very fact that so many chance-based juxtapositions can be found on the web tells us how diurnal L. mesomelas can be, where not persecuted by farmers.
 
Here is yet another (http://www.trulywildtours.com/wp-content/uploads/2014/08/jackal-springbok.jpg). The flank-band of this individual jackal is less graphic than those above, but the relationship between the two species is nicely shown and it is real food for thought that in this case a predator and its prey species are so analogous in colouration. By the way, both have conspicuous hindquarters, the difference being that the tail is the main element of this conspicuousness in the case of the predator.
 
The following Namibia:http://l7.alamy.com/zooms/83f7a1b5e073403baafd1a73d37ccb7d/black-backed-jackal-standing-lateral-canis-mesomelas-arjmr9.jpg
shows that, even when the animal is not directly lit, the flank-banding remains conspicuous. By the way, this also shows the typical appearance of the face of the southern African subspecies, which lacks the ‘pinched’ look of the cheeks of the East African subspecies.
 
The final photo (http://www.edrotberg.org/images/Black-backed%20Jackal.jpg) shows that the animal is about as conspicuous in longitudinal illumination as we saw in the last photo. I.e. in this photo-compilation we’ve seen that C. mesomelas has a flank-band of such precise configuration that it manages to remain conspicuous in various illuminations and when seen at various angles and distance. Why would this species want to self-advertise when other jackals do not?

 
  
The pattern on Canis mesomelas is often described as a ‘saddle’. This is not incorrect as much as tangential to what I suggest is the real nature of the pattern: a conspicuous flank-band, evolved for self-advertisement by tonal contrast (i.e. contrast between dark and pale) in as wide a range of daytime illuminations and settings as possible.
 
The crucial point about the flank-banding of C. mesomelas is that the band is not small or subtle (as might be seen as consistent with disruptive colouration, = camouflage) but gross, in the same sense as an exclamation mark is a gross feature of punctuation that is best used sparingly. Whereas most vulnerable animals are, as it were, coloured with a formula of commas, dot-dot, parentheses, and dashes – all of which disguise the silhouette and the shadows of the body to make the form blend into its environment in a tapestry of distracting detail – what C. mesomelas wears on the most visibile extensive surface of its pelage is the metaphorical equivalent of a road sign billboard announcing ‘attention’ or ‘look here’, at the same time as a flag announcing ‘I’m a black-backed jackal and I’m not trying to hide the fact’.
 
An important aspect of the configuration of the flank-band is that it is located high enough on the flank that the pale-fawn just ventral to it will usually catch the light, as opposed to being shades as the lower flanks tend to be shaded. What this means is that even if the grizzled ‘saddle’ does not stand out tonally from the background (i.e. is not noticeably paler than the background) than the upper flanks will stand out as noticeably pale, by virtue of their sharp juxtaposition with the blackish flank-band.
 
An interesting aspect of the fact that this ‘saddle’ consists of black-tipped hairs – instead of the fawn seen in the analogous flank-banding of e.g. gazelles – is that C. mesomelas retains the ability to communicate in a way unknown in gazelles: by raising its hackles in fear or anger, thus increasing its apparent height and size in a bid to intimidate an adversary. Because the medium-tone ‘panel’ in the profile, located above the dark flank-band, is grizzled grey rather than plain fawn, the jackal is able, by pilo-erection, to create a modest version of the sort of ‘bluff-crest’ taken to extremes by e.g. Hyaena hyaena and Proteles cristatus.
 
Please follow the captions for below for a more detailed explanation of how the exact configuration of flank-banding in C. mesomelas contrives to ensure that the animal remains as conspicuous as possible in various conditions of illumination.
 
The following shows that, in normal overhead sunlight, the upper flanks ‘light up’ in contrast to the darkest band on the upper flanks, thus providing maximal tonal contrast at a scale quite incompatible with any camouflage effect. Note also that although this pale fawn below the black band and the grizzled back above the black band are quite different hues and ‘textures’, they have effectively equivalent tones, i.e. they are about equally pale in contrast to the black band. Incidentally, this is C. m. schimdti with its ‘pinched’ face.
 
https://upload.wikimedia.org/wikipedia/commons/2/27/Chacal_chabraque.jpg
 
The following shows how the tonal contrast of flank-banding is preserved even when the animal is back-lit. The main factor preserving this tonal contrast is that, even when the fawn upper flanks are not directly lit and thus do not look particularly pale, the darkness of the black band is still sufficient to provide dark/pale contrast. Even when backlit, C. mesomelas tends to appear as an obvious horizontal bar standing out from its background, again inconsistent with camouflage but instead consistent with self-advertisement. Incidentally, this is C. m. mesomelas with a face free of the ‘pinched’ look of C. m. schmidti.
 
http://tawanablog.com/wp-content/uploads/2015/08/BEST106.jpg
 
The following shows that even in overcast lighting the tonal contrast on the flanks is sufficient to  distinguish the whole animal from its background. This once again is C. m. schmidti.
 
http://t02.deviantart.net/JMSESKNKu51UJrlyNPWx2fW-aNM=/fit-in/700x350/filters:fixed_height(100,100):origin()/pre11/0663/th/pre/i/2012/318/2/3/black_backed_jackal_i_by_track_maidens-d5l1fpp.jpg
 
Here we have, once again, C. m. mesomelas with a face lacking that obvious ‘shadow’ just under the ‘cheekbones’ that allows recognition of C. m. schmidti. What this photos shows is that the countershading functions much as it does in cryptically coloured mammals such as reedbucks: it compensates for the shading, and thus darkening of ventral surfaces of the body. Countershading makes the animal look ‘flat’, something normally associated with a strategy of ‘hiding in plain sight’ in most plain-coloured animals including the female Panthera leo. But the nice thing is that in C. mesomelas this ‘flatness’ merely enhances the conspicuousness, because it allows the tonal contrast on the flanks to seem even more at odds with the whole background, including the rest of the animal itself (except, of course, for the conspicuously dark and bushy tail).
 
https://thumb1.shutterstock.com/display_pic_with_logo/317785/318457688/stock-photo-kruger-national-park-black-backed-jackal-canis-mesomelas-318457688.jpg
 
The following shows how pilo-erection of the fur on the back, under emotions of anger or fear, temporarily mutes the flank-banding in favour of producing a crest of sorts, which is tonally contrasting enough in its own right to serve a different agenda of self-advertisement: i.e. to exaggerate the animal’s height and size. Thus, the ‘saddle’ is configured to perform two effects of tonal contrast, explaining why this species of jackal is ‘silver-backed’ as opposed to merely fawn-backed with a gazelle band on the flank.
 
https://thumb1.shutterstock.com/display_pic_with_logo/60660/379107577/stock-photo-black-backed-jackals-canis-mesomelas-in-aggressive-interaction-kalahari-desert-south-africa-379107577.jpg

what I meant about C. mesomelas being flank-banded rather than ‘saddled’. The crucial points are that a) the grizzled ‘saddle’ has a black ventral margin, which is the central feature in the flank-banding of tonal contrast, and b) the fawn of the flanks just ventral to this black band is not just ground-colour fawn, but a particularly pale fawn, much paler than the fawn of the haunch, such that there is maximal pale-dark contrast with the black band. Because the black band is located as high on the flanks as it is, the pale-fawn upper flank below it will usually be high-lit by the sunshine, as opposed to being shaded as the lower flanks would tend to be. The overall effect is for the whole animal to stand out from its environment even when the ‘auxiliary’ feature of conspicuousness, namely the dark bushy tail, is covered by vegetation./Were it more apt to think of this species as ‘saddled’, then what I would have expected are a) the grizzled saddle to lack the emphatically dark ventral margin that it in fact does possess, b) the fawn of the upper flanks to be no paler than the fawn elsewhere.

(writing in progress)

Posted on September 4, 2022 11:44 PM by milewski