25 de julho de 2021

Does any felid have aposematic colouration on the face?

Everyone knows that aposematic colouration - such as the bold black-and-white of skunks (Mephitidae, e.g. https://www.mymove.com/pest-control/guides/remove-skunks/) - is designed to warn enemies off. And everyone is familiar with many examples from wasps (https://www.whitehorse.vic.gov.au/waste-environment/trees-and-gardens/wildlife-guests-and-pests/pests/european-wasps) to the blue-ringed octopus (https://www.divescotty.com/underwater-blog/blue-ringed-octopus.php).

However, it is easy to overlook a certain principle: that emphasising the hazard is necessary mainly because the defensive capabilities of the animals involved are not obvious from anatomy or behaviour.

In other words, the idea behind aposematic colouration is not merely 'Beware!', it is 'I am much more dangerous than I look'.

That skunks could possibly smell so bad is not obvious to the uninitiated; the sting of wasps is hardly a visible feature of their anatomy; and the venom of the blue-ringed octopus is neither self-evident nor predictable based on previous experience with other octopuses. Hence it pays these animals to advertise, not just with threatening postures but also with colouration so bold that it gives pause to antagonists to consider 'What does this creature know that I do not?'

Our scientific descriptors should reflect this distinction: between colouration that emphasises obvious weaponry and colouration that hints at hidden weaponry. And the term 'aposematic' basically refers to the latter, not so?

Keeping all of this in mind, what should we call the bold colouration on the faces of the puma (Puma concolor, https://www.wallpaperflare.com/look-face-background-portrait-wild-cat-puma-cougar-wallpaper-ycqko) and the caracal (Caracal caracal, https://www.dreamstime.com/royalty-free-stock-photo-caracal-months-old-front-brown-background-image39254235)? Several genera of felids have fang-baring expressions, but these species are odd. Their facial fur has a permanent pattern of dark-and-pale which becomes 'warpaint' when the face is contorted in threat (https://www.dreamstime.com/royalty-free-stock-photo-snarling-puma-image16410455 and https://www.dreamstime.com/stock-photo-snarling-caracal-buffelsfontein-gme-nature-reserve-south-africa-image42818107 and https://www.youtube.com/watch?v=v3E_jK8By3c).

It is true that felids do possess 'hidden weapons' in the sense of their retractile claws, which in most species are actually more dangerous - particularly to the eyes - than the canine teeth. And so, when a cat fang-bares, there is a case to be made that what is being hinted at is the scratch rather than the bite.

However, neither the puma nor the caracal has weaponry beyond that of other felids. Furthermore, the Canada lynx (Lynx canadensis, https://en.wikipedia.org/wiki/Canada_lynx and https://www.youtube.com/watch?v=eaXmIPHrHmY) is reluctant to use a fang-baring expression, despite having disproportionately large feet (see https://www.youtube.com/watch?v=vAmkt_cYkuA and https://www.youtube.com/watch?v=niJg7Q1XLyU) and, presumably, claws. So why the specific emphasis, and do the facial colourations of puma and caracal qualify as 'aposematic'?

One possible explanation is that these two species, for ecological and biogeographical reasons, were not encountered frequently enough for their enemies to become familiar with them. The puma overlapped in habitat with the wolf and the brown bear, but the felid avoided contact by being nocturnal and hiding in trees and rocky outcrops. The caracal coexists with a diverse fauna of carnivores larger than itself, but is perhaps the most secretive felid in most of its habitat. According to this rationale the main value of their fang-baring displays may be to startle and confuse naive antagonists, stalling any attack. And if so, it might be appropriate to call their facial colourations 'flags'. But would it contort the adjective 'aposematic' to apply it here?

Publicado em 25 de julho de 2021, 10:41 TARDE por milewski milewski | 1 comentário | Deixar um comentário

Why the African clawless otter is tenfold brainier than the African striped weasel

Everyone knows that the human species is brainier than various other kinds of primates. However, what is not widely realised is how much brainier some carnivores are than others.

Figures for the braininess of 30 species of carnivores living near the southern tip of Africa can be found in https://www.tandfonline.com/doi/pdf/10.1080/02541858.1984.11447899. This information has been available for nearly three decades, but it is worth repeating in plain language, because the findings may still surprise naturalists.

Among those studied by measuring brain volumes relative to body mass, the species closest to average (i.e. with an encephalisation quotient of about 1.0) are the Cape fox (Vulpes chama, https://en.wikipedia.org/wiki/Cape_fox#/media/File:Vulpes_chama_(Etosha).jpg), the aardwolf (Proteles cristatus, https://en.wikipedia.org/wiki/Aardwolf#/media/File:Proteles_cristatus1.jpg), the marsh mongoose (Atilax paludinosus, http://portugal.inaturalist.org/taxa/41919-Atilax-paludinosus) and a range of felids weighing from less than 5 kg to more than 100 kg.

Note that most wild cats are about as brainy as expected for the average mammal, including the average carnivore.

However, three species are about twice as brainy (encephalisation quotient about 2.0) as this standard would predict. These are the African clawless otter (Aonyx capensis, https://upload.wikimedia.org/wikipedia/commons/6/69/Aonyx_capensis%2C_male%2C_Shamvura.jpg), the honey badger (Mellivora capensis, https://en.wikipedia.org/wiki/Honey_badger#/media/File:Mellivora_capensis_in_Howletts_Wild_Animal_Park.jpg) and the African hunting dog (Lycaon pictus, https://upload.wikimedia.org/wikipedia/commons/b/ba/African_wild_dog_%28Lycaon_pictus_pictus%29.jpg). This kind of otter has primate-like dexterity; the honey badger is smart enough to use tools even though it is not dexterous; and the African hunting dog uses extreme teamwork to compete with, and evade punishment from, felids and hyenas with far more brawn.

Also on the brainy side are the brown hyena (Parahyaena brunnea,

https://upload.wikimedia.org/wikipedia/commons/5/50/Brown_Hyena_%28Hyaena_brunnea%29_leaving_waterhole_..._%2850915531592%29.jpg),

caracal (Caracal caracal, https://upload.wikimedia.org/wikipedia/commons/1/12/Caracal_on_the_road%2C_early_morning_in_Kgalagadi_%2836173878220%29.jpg)

, black-backed jackal (Lupulella mesomelas, https://en.wikipedia.org/wiki/Black-backed_jackal#/media/File:Black-backed_jackal_(Canis_mesomelas_mesomelas)_2.jpg) and spotted-necked otter (Hydrictis maculicollis, https://en.wikipedia.org/wiki/Spotted-necked_otter#/media/File:Spotted-necked_otter_1.jpg). These share encephalisation quotients of about 1.3, despite belonging to four different families.

Somewhat below average in braininess is the diminutive, shy black-footed cat (Felis nigripes, https://en.wikipedia.org/wiki/Black-footed_cat#/media/File:Zoo_Wuppertal_Schwarzfusskatze.jpg). This has a similar encephalisation quotient (about 0.7) to the like-size Egyptian mongoose (Herpestes ichneumon, https://www.naturepl.com/stock-photo-egyptian-mongoose-herpestes-ichneumon-captive-at-friguia-park-tunisia-image01507979.html).

Surprisingly limited in braininess are the genets and most mongooses, including the meerkat (Suricata suricatta, https://upload.wikimedia.org/wikipedia/commons/9/9a/Meerkat_%28Suricata_suricatta%29_Tswalu.jpg). Given the smart, social behaviour and anthropomorphic appeal of this species, it is hard to believe that its encephalisation quotient is only 0.3. Equally unexpected is that the common dwarf mongoose (Helogale parvula, https://upload.wikimedia.org/wikipedia/commons/0/05/Dwarf_Mongoose_%28Helogale_parvula%29_%286002158282%29.jpg), another social species, has an encephalisation quotient of less than 0.2, tenfold less than that of the most social canid, the African hunting dog.

Least brainy is the African striped weasel (Poecilogale albinucha, https://en.wikipedia.org/wiki/African_striped_weasel#/media/File:Whitenapedweasellg2.jpg), which means that the family Mustelidae spans the full range of values found in this study. The African striped weasel (0.16) and the striped polecat (Ictonyx striatus, encephalisation quotient 0.3, https://www.agefotostock.com/age/en/details-photo/africa-namibia-private-reserve-striped-polecat-or-african-polecat-ictonyx-striatus-captive/D88-3525771) both have warning colouration and rely on noxious substances, not intelligence, to avoid victimisation by other carnivores.

Publicado em 25 de julho de 2021, 04:28 MANHÃ por milewski milewski | 0 comentários | Deixar um comentário

24 de julho de 2021

Extreme fang-baring displays: examples in African carnivores

Mammalian carnivores include felids, canids, hyenids, mustelids, herpestids, viverrids and others (https://en.wikipedia.org/wiki/Carnivora). All have canine teeth as an important part of their weaponry. All are likely to defend themselves by biting, and all might be expected to show their canines as a deterrent to would-be attackers.

However, fang-baring displays are surprisingly variable among carnivores, even within a given family.

Most families of carnivores lack fang-baring displays beyond just the opening of the mouth. It is only in felids, some canids and a few mustelids that displays of the upper canines are well-developed. Even within the felids and canids, there is surprising variation in the facial expressions both anatomically and in terms of patterns of colouration which accentuate the displays.

This variation can be illustrated, within the African fauna, by means of just four species: the leopard (Panthera pardus), the caracal (Caracal caracal), the African golden wolf (Canis anthus) and the black-backed jackal (Lupulella mesomelas).

Several genera of felids have fang-baring displays, but what varies greatly is the associated colouration. The face of the leopard has completely inconspicuous colouration, which means that the fang-baring expression is purely a matter of exposing the pale canines and dark lips (https://photos.com/featured/close-up-of-leopard-growling-wim-van-den-heever.html?product=art-print and https://dissolve.com/stock-photo/Leopard-growling-Greater-Kruger-National-Park-South-royalty-free-image/101-D1028-85-811). By contrast, in the caracal there is a 'warpaint' effect owing to dark/pale contrasts on the fur, which change shape as the face is contorted (https://www.agefotostock.com/age/en/details-photo/caracal-caracal-caracal-felis-caracal-spitting-namibia/BWI-BS356922/1 and https://www.agefotostock.com/age/en/details-photo/caracal-felis-caracal-spitting-snarling/BWI-BLW029571/1). This 'ominous makeup' is restricted to only a few species of carnivores, all of them felids. And by the same token some felids, such as the Canada lynx (Lynx canadensis), hardly fang-bare at all, let alone possess associated colouration.

Canids vary surprisingly in the incidence of fang-baring displays, and it is in the genus Canis that they are extremely developed. In the African golden wolf the face is contorted even more than in felids (https://en.wikipedia.org/wiki/African_golden_wolf#/media/File:Canis_anthus_threat_postures.png and https://external-preview.redd.it/MyxvFu3vsXJzYXbspo-m6GkfcfUMUSnNc6Hlyasjtnw.jpg?auto=webp&s=faaaab5cc13276a4c07bd8f742bbb68554847603 and https://stock.adobe.com/images/a-golden-jackal-animal-in-anger-and-fight-mode-in-nature/246623708). By contrast, the face of the black-backed jackal remains uncontorted regardless of the intensity of emotion (https://www.flickr.com/photos/mvukovich_digiscope/40485635433/ and http://lh4.ggpht.com/-nCRTnIZrjzk/TwRubSUqKpI/AAAAAAAAOMY/kVHcbbU0ZiQ/s1600/vulture-jackal_1858443i%25255B4%25255D.jpg and https://www.gettyimages.co.uk/detail/photo/two-black-back-jackals-fighting-by-a-waterhole-royalty-free-image/1204595106?adppopup=true and https://www.naturepl.com/stock-photo-black-backed-jackals-fighting-canis-mesomelas-savute-chobe-national-nature-image01117639.html and https://www.naturepl.com/stock-photo-canis-mesomelas-nature-image00761070.html and https://www.dreamstime.com/two-black-backed-jackals-fighting-snarling-each-other-jackals-fighting-teeth-showing-image106825166 and https://www.kimballstock.com/popuppreview.asp?db=a&image=AFW+26+MH0003+01&itemw=4&itemf=0001&itemstep=1&itemx=16).

So here is food for thought. The caracal and the black-backed jackal coexist widely, have similar body sizes, and are persecuted by the same guild of larger carnivores. Why would their modes of self-defence differ so much in the displaying of the upper canines?

Publicado em 24 de julho de 2021, 10:00 TARDE por milewski milewski | 6 comentários | Deixar um comentário

Why is the black-backed jackal the only carnivore marked like a gazelle?

The black-backed jackal (Lupulella mesomelas) differs from jackals in the genus Canis, as well as all other Carnivora, in possessing a gazelle-like pattern of colouration on the flanks (see https://f.hubspotusercontent30.net/hubfs/8820531/Imported_Blog_Media/jackal-springbuck-throat-web-3.jpg and https://www.flickr.com/photos/77236126@N00/48051508477/ and https://www.flickr.com/photos/bwildlife/17167029101). Why is it unique in this way?

The important point about this pattern is its relative conspicuousness. Most carnivores have inconspicuous colouration (e.g. see Canis anthus https://www.istockphoto.com/photo/golden-jackal-gm494430463-40577222), which makes sense because they hide not only from their prey but also from more powerful carnivores. In canids, the usual pattern is cryptic, i.e. plain-coloured with countershading. Any markings tend to be disruptive in the sense of camouflaging the figure. However, in the black-backed jackal the banding on the side of the body is stark enough, in some illuminations, to make the whole figure stand out from its background.

The following photos of the eastern subspecies (C. m. schmidti) illustrate this effect:
https://www.inaturalist.org/observations/69464499
https://www.inaturalist.org/observations/61773370
https://www.inaturalist.org/observations/54028534
https://www.inaturalist.org/observations/53916862
https://www.inaturalist.org/observations/45065585
https://www.inaturalist.org/observations/39544578
https://www.inaturalist.org/observations/34923025
https://www.inaturalist.org/observations/18736945
https://www.inaturalist.org/observations/10002908
https://www.inaturalist.org/observations/5300649
https://www.inaturalist.org/observations/2794845
https://www.inaturalist.org/observations/1065617
https://www.inaturalist.org/observations/843652

Among all canids worldwide, the black-backed jackal is the species living in the most intensely predatory regime. It coexists, and to a remarkable extent competes, with the full spectrum of large carnivores in the environments richest in prey antelopes on Earth, those of acacia savanna in eastern and southern Africa.

The black-backed jackal is inferior in the predatory/scavenging hierarchy to lion, spotted hyena, leopard, cheetah, African hunting dog, and brown hyena/striped hyena; and the leopard kills it not for spite but for food (see https://i.redd.it/bezcb4s8d0s41.jpg). Yet it manages to be a considerable predator of antelopes in its own right (e.g. see https://www.youtube.com/watch?v=nD9MkAbgl-o and https://www.earthtouchnews.com/natural-world/predator-vs-prey/watch-antelope-flees-hunting-jackals-while-an-eagle-attacks-from-the-air/), and even more remarkably is the most diurnal of jackals with the exception of the Ethiopian wolf (Canis simensis). Daytime activity makes hiding difficult but compensates to some degree for the extreme risk of victimisation, because the leopard in particular tends to rest at the bright, warm time of day. At the same time, the black-backed jackal is, among all these carnivores, the one most reliant for hunting and self-defence on close cooperation of monogamous partners.

What this suggests is that the black-backed jackal has adopted conditionally conspicuous colouration according to the same adaptive trade-off as the gazelles it hunts. It compromises between the ability to hide and the ability to monitor the location and activity of group-members at the briefest glance, in a strategy of extreme cooperative vigilance and social coordination, rather than merely keeping a low profile.

The black-backed jackal and the Ethiopian wolf are similarly diurnal, and both have conspicuous aspects to their colouration. So why do they accentuate different parts of their bodies (see my Journal Post of July 23)? Whereas the former species signs its torso, the latter signs its hindquarters and forefeet. One difference is that the Ethiopian wolf hunts its rodent staples alone, whereas the black-backed jackal depends on pairwork to overcome its favourite prey, namely antelopes. Another difference is in the respective predatory regimes, the high-altitude meadows of Ethiopia being beyond the range of most species of large carnivores - as well as gazelles or any other antelopes more gregarious than the plain-coloured bohor reedbuck (Redunca redunca).

Publicado em 24 de julho de 2021, 07:18 MANHÃ por milewski milewski | 0 comentários | Deixar um comentário

23 de julho de 2021

Why is there a caudal flag in leopard but not puma or jaguar?

The leopard (Panthera pardus), the puma (Puma concolor) and the jaguar (Panthera onca) are like-size ecological counterparts on different continents. All have long tails, which they tend to twitch when excited.

However, the leopard alone has a caudal flag, which is sometimes activated while walking in daylight. And it is an extreme example of a caudal flag, even compared to deer and other ruminants (see https://www.youtube.com/watch?v=sWo7BiyDT04 and https://www.youtube.com/watch?v=LoVG75u72SQ).

The conspicuousness of the leopard's tail is owing to its white ventral surface, which is exposed by curling the tail up to various heights (see https://www.alamy.com/leopard-panthera-pardus-tail-botswana-image184121172.html and https://www.alamy.com/leopard-panthera-pardus-side-body-face-looking-back-eyes-long-whiskers-tail-curled-up-partially-hidden-by-grass-samburu-national-reserve-kenya-africa-image242458468.html and https://www.alamy.com/leopard-panthera-pardus-walking-on-savanna-masai-mara-national-reserve-kenya-africa-image401804791.html and https://www.alamy.com/stock-photo-leopard-panthera-pardus-in-the-savannah-masai-mara-kenya-123182747.html and https://www.alamy.com/african-leopard-panthera-pardus-pardus-adult-male-at-dusk-going-to-a-waterhole-kruger-national-park-south-africa-africa-image243578242.html).

The puma has a tail of similar dimensions, but its inconspicuous tip is not curled up while walking (https://www.youtube.com/watch?v=2bqgh40e6hU and https://www.mindenpictures.com/stock-photo-patagonian-puma-puma-concolor-patagonica-female-walking-over-open-naturephotography-image90744095.html and https://www.catster.com/the-scoop/see-mountain-lions-or-pumas-in-chile-patagonia and https://www.alamy.com/cougar-in-the-snow-5-image188075869.html). The jaguar, although belonging to the same genus as the leopard, has a relatively short, tapering tail with an inconspicuously dark tip (https://www.youtube.com/watch?v=flVdCHC1v-A and https://www.alamy.com/stock-photo-jaguar-drinks-water-70166563.html and https://www.alamy.com/stock-photo-jaguar-walking-in-a-shady-area-of-the-riverbank-of-the-cuiaba-river-136707647.html).

Why is the leopard the species with a showy tail?

On their American supercontinent, the puma and the jaguar are the top predators in their main habitats. By contrast the leopard everywhere coexisted with the tiger (Panthera tigris, in Asia), the lion (Panthera leo, in Africa and part of Eurasia) and/or the spotted hyena (Crocuta crocuta, in Africa and formerly in extratropical Eurasia) - all of which outrank it in a hierarchy of violence.

Superior carnivores are routinely inimical towards inferior carnivores, stealing their prey and also killing them for the sake of killing, at every chance. Thus the leopard is at continual risk, both while patrolling its territory and in the interval between catching prey and hoisting it into a tree. If the superior carnivores hear a ruckus, they are likely to run towards the noise to capitalise on an opportunity for both food and gratuitous murder.

The main prey species of the leopard play on this vulnerability: when they spot the predator they not only denounce it, they embarrass it in what can seem like a superfluously noisy way. The snorts, hoots and barks of e.g. impala (Aepyceros melampus, https://www.youtube.com/watch?v=U_GbVH8AOEY), chital (Axis axis, https://www.youtube.com/watch?v=hODA3OEzvaU and https://www.youtube.com/watch?v=WHrINU-E9Sk), sambar deer (Rusa unicolor, https://wildambience.com/wildlife-sounds/sambar-deer/), baboons (Papio spp., https://www.youtube.com/watch?v=za839cpwUh0) and langurs (Semnopithecus spp., https://www.youtube.com/watch?v=khxxVOg2Gtw) can be so frenetic and sustained that they seem beyond any purpose of informing each other or letting the leopard know that it has lost the element of surprise.

Could it be that the prey animals are calling in the superior carnivores to prosecute the leopard?

It is hardly surprising that, once the stalking leopard is spotted, it tends to reveal itself. What is surprising is that it tends to walk off in the open with its caudal flag activated. Since it lacks credibility in protesting its innocence, could this be a case of exaggerated appeasement?

Further observations are needed, comparing daytime and nighttime, to test whether the caudal flag reassures ruminants or monkeys to the degree of quieting them down and curtailing the risk from superior carnivores (https://www.youtube.com/watch?v=EuZo4PkIti4). However, if so this would mean that the caudal flag is an anti-predator adaptation, albeit one mediated by the leopard's prey animals.

The leopard is both killer and victim, whereas the puma and the jaguar tend to be unambivalent killers. For the leopard, better to raise a flag of surrender to the whistleblowing prey than risk the arrival of those to which surrender means death. So, does the leopard emulate various species of ruminants in possessing a caudal flag because it - more than any comparable big cat - remains vulnerable even as predates?

Publicado em 23 de julho de 2021, 10:33 MANHÃ por milewski milewski | 0 comentários | Deixar um comentário

Advertisement colouration in a carnivore: the Ethiopian wolf

The Ethiopian wolf (Canis simensis, see https://www.youtube.com/watch?v=ROU7vh2QJTM and https://www.youtube.com/watch?v=mbvoqwhMvr8) is a stalking carnivore, which approaches its prey stealthily by day on high-altitude meadows. Therefore, the inconspicuousness of its overall colouration is unsurprising.

However, where the Ethiopian wolf differs from most other Canidae, instead resembling certain antelopes and deer, is in its pedal and caudal flags. These make this species particularly photogenic.

The pattern on the face, throat and chest disrupts the approaching figure, making the predator inconspicuous to the prey it faces during stalking (see
https://www.istockphoto.com/photo/close-up-of-endangered-ethiopian-wolf-gm1151550965-312121323 and https://www.istockphoto.com/photo/close-up-of-a-rare-and-endangered-ethiopian-wolf-gm1215528860-354067674 and https://www.istockphoto.com/photo/rare-and-endangered-ethiopian-wolf-gm1161002244-317982362).

However, the pattern on the hindquarters is bolder (see https://www.flickr.com/photos/graham_ekins_world_wildlife/6577081283 and https://www.inaturalist.org/observations/8730906 and http://www.africaimagelibrary.com/-/galleries/east-africa/ethiopia/-/medias/e2e29d0a-1a00-11e0-b123-432bf5092cc3-ethiopian-wolf-canis-simensis-sanetti-plateau-bale-mountain). While it is not striking enough to reveal the stationary figure, it becomes eye-catching when the animal moves (see https://www.youtube.com/watch?v=XxuB6jTLRUo). I would call it a caudal flag, functioning for social cohesion in this slightly gregarious species. However, it differs from most caudal flags in ungulates in that the tail is not routinely raised or wagged.

The caudal flag of the Ethiopian wolf is not unique, because e.g. some individuals of the side-striped jackal (Canis adustus) have a comparable pattern (see https://parody.fandom.com/wiki/Side-Striped_Jackal?file=Jackal%252C_Side-Striped.jpg).

However, what is unique to the Ethiopian wolf is a pedal flag restricted to the forelegs.

The inner surface of the lower foreleg is anomalously pale, and tends to shine on pasture free of obstructing herbage. This applies particularly in the slanting light of morning and late afternoon. Although it lacks the dark emphasis seen on the tail, the pedal flag is conspicuous enough to accentuate the movement of walking or trotting. This aids social cohesion more secretively than does the caudal flag, because the signal is low on the figure and on a surface which tends to be shaded when the sun is brightest (see https://www.istockphoto.com/photo/close-up-of-a-rare-and-endangered-ethiopian-wolf-gm1215528263-354067637 and https://www.istockphoto.com/photo/ethiopian-wolf-in-the-bale-mountains-national-park-in-ethiopia-gm1045923160-279876857 and https://www.agefotostock.com/age/en/details-photo/abyssinian-ethiopian-wolf-simien-jackal-simien-fox-endangered-canis-simensis/MEV-10777461 and https://wildkratts.fandom.com/wiki/Ethiopian_Wolf?file=Ethiopian+Wolf+RL.PNG and https://animalia.bio/ethiopian-wolf and https://www.istockphoto.com/photo/close-up-of-a-rare-and-endangered-ethiopian-wolf-gm1128477421-297789122 and https://www.istockphoto.com/photo/ethiopian-wolf-sanetti-plateau-bale-mountains-ethiopia-gm1094020256-293614039).

The following photo (https://www.istockphoto.com/photo/group-of-ethiopian-wolves-in-the-highlands-gm1161748335-318430860) shows the caudal and pedal flags working together on the moving figures.

Publicado em 23 de julho de 2021, 05:04 MANHÃ por milewski milewski | 1 comentário | Deixar um comentário

22 de julho de 2021

The blue wildebeest: incongruously straddling the 19th and 21st centuries

Everyone knows that the blue wildebeest (Connochaetes taurinus) looks incongruous: part buffalo, part cow, part antelope, and part clown. And everyone who has hunted it knows that it is incongruously tough: where it takes one bullet to drop a hartebeest, it takes three before the deceptively spindly legs buckle under a blue wildebeest.

But what few may realise is that - owing to a particular comedy of errors - the blue wildebeest is also chronologically incongruous. Part of it has remained pre-Great Trek, while for another part the Future has arrived with a bang.

At the beginning, the big game of southern Africa was hunted science-free. Then, gun-toters arrived and started to send specimens to European museums, so that the big game could be classified according to the Linnaean system. Once the species were formally named, subspecies became valuable in the chase. Not only did landowners reintroduce big game for the purposes of hunting, but it mattered to tell a blesbok from a bontebok. About then, a new wave of foreign hunters began to fly to southern Africa just to hunt, ticking off lists of not only species but also varieties. In the hunters' sights, the exact identity of the quarry mattered more and more, and game owners started to add 'over-the-top' variety by artificially breeding mutant forms (https://www.somerbysafaris.com/album/hunting-a-golden-wildebeest and https://realorasafaris.co.za/product/king-wildebeest/).

This progression went from primitive (pre-1700) through crudely taxonomic (1700-1900) to finely taxonomic (1900-2000). Then it proceeded to 'post-taxonomic' (post-2000) in the sense that no scientist really knows how to 'classify' a gnutant created by breeding in a farm paddock since the turn of the millennium.

What makes the blue wildebeest incongruous in this progression is that, owing to the vagaries of historical accident and human fallibility, it has managed to remain lost in the nineteenth century even as it has become adulterated by the twenty-first century.

To this day, there survives in the wild a consistently recognisable, widespread and common subspecies of the blue wildebeest which hunters fail to realise is a subspecies at all: the western wildebeest (C. t. mattosi). Compare the western wildebeest (https://www.inaturalist.org/observations/5058324) with the 'standard' blue wildebeest (https://www.inaturalist.org/observations/11283917).

The western wildebeest is available to unknowing hunter-tourists in most of the hunting blocks of Botswana and Namibia. The outfitters and ranch-owners could charge more for this as a particular kind of wildebeest. However, they do not even know the kind exists, because the subspecies-names given to it, namely mattosi in 1925 and borlei in 1933, have both in turn, and for no good reason, fallen through the cracks of taxonomic recognition (see my Journal Posts of July 13 & 14, 2021, https://www.inaturalist.org/journal/milewski). And even more incongruously, this ignorance may persist for decades to come, because of a reluctance by scientists to admit the embarrassment of a series of oversights which has lasted nearly two centuries.

Based on past trends, the scientists gate-keeping the nomenclature of big game may persist with a shifting of the onus of recognition of this obvious kind of wild wildebeest, based on little more than cognitive dissonance. "We haven't seen this as a different wildebeest, so how can we see it as such until you prove it genetically?"

Meantime, oblivious to the opportunity to stock their properties with western (taurinus mattosi) as well as nominate blue (taurinus taurinus) wildebeest, those catering to the hunting industry will continue to breed new kinds of gnutants (https://www.farmersweekly.co.za/animals/game-and-wildlife/rise-fall-future-colour-variants/), even if this compromises the genetic integrity of the nominate subspecies as a whole on private land (https://theconversation.com/conservation-versus-profit-south-africas-unique-game-offer-a-sobering-lesson-82029). It seems inevitable that gnu-farmers will embrace hybridisation between the blue and the black (Connochaetes gnou) wildebeest as a source of extra genetic combinations, whether openly or secretively. And so we face a future in which even the gross distinction between the original species of wildebeest may be permanently blurred.

Are we not heading towards a clown-world 2030 in which hunters are still denied the realisation of a wild and natural subspecies, the western wildebeest, even as what is offered as the standard blue wildebeest has already become quasi-domesticated?

And the irony? Two of the first-ever (pre-1840) scientific paintings of the wildebeest are actually instantly recognisable - by virtue of the upright mane, long beard, and minimal brindling - as the western wildebeest (http://heritage-prints.squarespace.com/#/wildlife/ and https://www.prints-online.com/connochaetes-taurinus-blue-wildebeest-14238740.html#openModal and https://elizabethgordon.co.za/artworks/wildebeest-wch). William Cornwallis Harris (https://en.wikipedia.org/wiki/William_Cornwallis_Harris) saw it for what it was in the nineteenth century, but this subspecies continues to hide in plain sight - in some sort of time-warp - as we photograph it on our smartphones today.

Publicado em 22 de julho de 2021, 10:28 TARDE por milewski milewski | 0 comentários | Deixar um comentário

19 de julho de 2021

Was the blue wildebeest a newly-clothed emperor in the eyes of the hunter-explorers?

How many iNaturalists can see any blue in the colouration of the blue wildebeest (Connochaetes taurinus taurinus)? For example, see https://www.inaturalist.org/observations/38573826 and https://www.inaturalist.org/observations/28361284 and https://www.inaturalist.org/observations/49703363.

This is what I think may be going on.

There is an element of adaptive conspicuousness in the colouration of wildebeests. It pays these gregarious, self-advertising animals to be easily visible to each other and predators by day, while remaining able to blend into the darkness of night (see my Journal Posts 'Adaptive colouration in wildebeests: parts 1 and 8', July 2021, in https://www.inaturalist.org/journal/milewski?page=2). So the conspicuous paleness of the rump in certain perspectives (e.g. see https://www.inaturalist.org/observations/29077207) is achieved not by depigmentation but by reflective qualities of the texture and microstructure of the hairs. These work at the brightest times of day to give a conspicuous sheen, but 'switch off' conveniently at night.

I go on to hypothesise as follows.

Both wildebeests and their predators are naturally 'colour-blind' in a similar way to red-green colour-blind men (see https://www.color-blindness.com/red-green-color-blindness/ and https://en.wikipedia.org/wiki/Dichromacy) and they tend to see in the blue-violet-ultraviolet range of wavelengths more than humans can (https://www.themeateater.com/wired-to-hunt/whitetail-hunting/deer-vision-how-whitetails-see-color-light-and-movement). What this would mean is that the sheen on the wildebeest's rump in the midday sun, modest in human eyes, looks glaring to the animals themselves. And then is invisible at night.

One of the oddities of red-green colour blindness in humans is that it is compensated by an increased sensitivity to ultraviolet. Perhaps this evolved to give ancestral hunters a spectrum of individual talents in which some men could read tracks and spot game or venomous snakes free of the distracting effects of full-colour vision.

I suspect that, among the first gun-toters who reached far enough north in South Africa to encounter Connochaetes taurinus taurinus for the first time, about one in twenty were ultraviolet-sensitive (= red-green colour-blind). These individuals saw the wildebeest as obviously bluish. And their fellows, although outnumbering them 20 to one, were reluctant to admit that they could not see the blue. At the same time, there was nothing else so obviously odd about this rather bovine animal that made for a competitively apt name. And so the name 'blouwildebees' stuck.

And it continues to stick today (https://en.wikipedia.org/wiki/Blue_wildebeest), because none of us, the silent majority mystified by the adjective, wants to be first in calling out the Emperor's New Clothes. We subconsciously assume that someone knows, or sees, better than us, so we go along with a harmless misnomer.

And the delightful irony is that, in the wildebeests' own eyes, they are indeed in a meaningful sense blue: cavorting mirrors under the African sky.

Publicado em 19 de julho de 2021, 07:44 TARDE por milewski milewski | 0 comentários | Deixar um comentário

18 de julho de 2021

Why was Angola the Empty Quarter for African large mammals?

Angola (https://upload.wikimedia.org/wikipedia/commons/8/89/Angola_%28orthographic_projection%29.svg) is a vast, well-watered country in south-central Africa. Its human population is about as sparse as in Tanzania. However, the natural abundance of large wild mammals is surprisingly different between these two countries, even considering the effects of a decades-long war of attrition in Angola. At the time when European explorers arrived, most of the country had only sparse populations of a limited fauna of ungulates.

The human population densities of Angola and Tanzania can be compared in https://databasin.org/maps/698e24d966b74684a7634ba2851f15b5/.

The paucity and scarcity of large mammals was particular to the extensive mesic savannas of the central plateau: miombo woodland with dambos (grassy openings along drainage lines). See file:///C:/Users/Antoni%20Milewski/Downloads/Beja2019_Chapter_TheMammalsOfAngola.pdf.

Here, the only species of ruminants during the period of Portuguese colonisation were bush duiker (https://www.zoochat.com/community/media/angolan-common-duiker-sylvicapra-grimmia-splendidula.487190/), southern reedbuck (https://en.wikipedia.org/wiki/Southern_reedbuck#/media/File:Redunca_arundinum_range_map.png and https://en.wikipedia.org/wiki/Southern_reedbuck#/media/File:Southern_Reedbuck_(Redunca_arundinum)_iSimangaliso_Wetland_Park,_KwaZulu-Natal,_South_Africa.jpg), defassa waterbuck (https://www.africahunting.com/media/crawshays-defassa-waterbuck-zambia.3015/), roan antelope (https://www.expertafrica.com/wildlife/roan-antelope/zambia), common eland (https://en.wikipedia.org/wiki/Common_eland#/media/File:Common_eland_mara.jpg and https://upload.wikimedia.org/wikipedia/commons/1/12/Common_eland.png), and African buffalo. Most of these are unusually widespread species in subSaharan Africa generally, and their populations were naturally sparser in Angola than elsewhere.

Species common in Tanzania in comparable 'moist-dystrophic' savannas, such as Sharpe's grysbok, oribi (https://www.istockphoto.com/photo/oribi-on-the-liuwa-plains-zambia-africa-gm505505165-44644896), impala, Lichtenstein's hartebeest, sable antelope, and greater kudu, were scarce or marginal in central Angola. The only species more reliably present in Angola than in southern Tanzania was the roan antelope.

This makes Angola the part of Africa most similar, in the near-emptiness of its verdant savannas for large mammals, to South America. In which environmental ways might the central plateau of Angola resemble the South American rather than the Tanzanian savannas?

One important factor in common is the homogeneous nutrient-poverty of the soils. The Angolan plateau is partly covered by deep Kalahari sand (https://www.researchgate.net/figure/Area-covered-by-Kalahari-Sands-in-Africa-after-Main-1987_fig4_260135414 and https://www.researchgate.net/figure/The-Kalahari-sands-and-sampling-locations-of-the-soil-profiles-The-Kalahari-sand-sheet_fig3_229428856). Under this rainy climate, leaching of nutrients has produced the most extensively depleted soils in Africa, particularly for phosphorus and zinc. The result - as in the cerrado of Brazil - is a 'green hell' for large animals, in which the vegetation grows copiously but is fibrous and unpalatable.

What makes the miombo woodlands of Tanzania more productive is the influence of the nearby Great African Rift, a geological disturbance supplying fresh sources of nutrients to nearby landscapes. Nutritious plants, such as acacias, grow here and there in the mosaic-like miombo savannas of southern and western Tanzania, in contrast to Angola where the dystrophic woodland interspersed with grassland along drainage lines is the most monotonous anywhere in Africa.

Publicado em 18 de julho de 2021, 07:49 MANHÃ por milewski milewski | 5 comentários | Deixar um comentário

17 de julho de 2021

The western wildebeest as an example of paedomorphic evolution

We have seen that the main differences of the western wildebeest (Connochaetes taurinus mattosi) from the blue wildebeest (Connochaetes taurinus taurinus) are:

the uprightness of the mane, the length of the beard (compare mattosi https://www.agefotostock.com/age/en/details-photo/blue-wildebeest-connochaetes-taurinus-adult-animal-foraging-in-the-high-grass-kgalagadi-transfrontier-park-northern-cape-south-africa-africa/ZI6-3564204 with nominate taurinus https://www.bigstockphoto.com/image-370276231/stock-photo-the-blue-wildebeest-%28connochaetes-taurinus%29%2C-also-called-the-common-wildebeest%2C-white-bearded-wildeb),

and the reduction of brindling (striping) on the body and cheeks (compare mattosi https://www.inaturalist.org/observations/32318148 and https://www.agefotostock.com/age/en/details-photo/blue-widbeest-connochaetes-taurinus-in-close-up-etosha-national-park-namibia/G69-302177 with nominate taurinus https://www.inaturalist.org/observations/37029798 and http://elelur.com/data_images/mammals/wildebeest/wildebeest-08.jpg).

Here I ask whether these differences have arisen paedomorphically, i.e. by the evolutionary retention of juvenile features.

It is well-known that in wildebeests the females in a sense mimic males, by having not only horns but also the kinds of hairy adornments typically associated with masculine aggression and the exaggeration of the male silhouette for the purposes of rivalry (see https://www.sciencedirect.com/science/article/abs/pii/016815919190264X). In all wildebeests, females and males have horns, manes and beards of similar size, which can make it hard to tell the sexes apart in the field.

However, what is easier to overlook is that there is also a kind of precociality in wildebeests, in which the mane and beard are proportionately more prominent in juveniles than in adults.

For example, compare these one year-old nominate taurinus (https://www.inaturalist.org/observations/19266906 and https://www.istockphoto.com/photo/close-up-of-a-wildebeest-standing-on-the-dry-plains-of-the-western-cape-south-africa-gm1193291491-339364166?irgwc=1&cid=IS&utm_medium=affiliate&utm_source=photostockeditor&clickid=xABUceQmnxyOWXNwUx0Mo3kTUkByqxxxtyGw3I0&utm_term=&utm_campaign=&utm_content=258824&irpid=1327686) with this adolescent (two year-old) nominate taurinus (https://www.agefotostock.com/age/en/details-photo/blue-wildebeest-connochaetes-taurinus-eating-grass-kruger-national-park-south-africa/ZI6-1930962, in which the beard has already shrunk proportionately).

For some reason all wildebeests already have visible manes and beards from birth (https://www.bigstockphoto.com/image-381100301/stock-photo-the-blue-wildebeest-%28connochaetes-taurinus%29%2C-also-called-the-common-or-white-bearded-wildebeest-or-b), which means that the growth of hair adornments takes a kind of priority in this genus. Starting ahead in this way means that the hair adornments appear advanced when the animal is still juvenile. (Although the precociality of the growth of the legs makes obvious sense in animals which run for their lives right from birth, the adaptive value of precocial growth of hair adornments is unclear.)

Furthermore, the mane is also still upright in juveniles (nominate taurinus https://www.inaturalist.org/observations/12485101), partly because the hairs are not yet long or spaced-out enough on the nuchal ligament to collapse as seen in adults of the nominate subspecies taurinus (as well as adults of all other forms of wildebeest besides Connochaetes gnou).

Turning to brindling:

the striping on the body and cheeks in wildebeests (see 'Adaptive colouration in wildebeests, part 4: brindling', July 09, 2021 in https://www.inaturalist.org/journal/milewski) is the opposite of precocial. The infant completely lacks brindling, which starts to appear only well after the ground-colour turns from fawn to greyish brown.

What this means is that, at the juvenile stage, the animal combines a prominent mane and beard with minimal brindling. And it is this very combination that persists into adulthood in subspecies mattosi.

In a sense, the appearance of the western wildebeest is that of 'overgrown juveniles' of the eastern, nominate subspecies - except of course for the horns, which do adopt the mature shape.

Now that we have an ontogenetic search-image, can we find evidence in our photos of the western wildebeest that, within adulthood, the really mature individuals are the ones with the most brindling (e.g. see https://www.inaturalist.org/observations/31787361)?

Publicado em 17 de julho de 2021, 09:41 TARDE por milewski milewski | 2 comentários | Deixar um comentário