Most of the external and morphological traits of the aurochs are well known to us thanks to numerous superb skeletal remains and also contemporaneous artworks and written sources. While the skeletal material is complete, well-preserved and numerous enough to give us a very precise picture of the aurochs’ morphology, its dimorphism in sex and also, to a certain degree, variation along time and region, artistic impressions and written accounts are sometimes not comprehensive or unambiguous enough to clear all open questions. Do not get me wrong, the picture of the aurochs we have is very precise. But there are some aspects that are questionable and still leave some room for speculation. In this post I give you overview over all those points that come to my mind.
The length of the dewlap
It is unquestionable that the aurochs had a dewlap of a certain size. Tropical bovines tend to have a large one (banteng, gaur, kouprey), more northern ones not so much (bison). Zebuine cattle have a large dewlap as well, probably both due to domestication and climate. The European aurochs, on the other hand, probably could not effort too much heat loss caused by a large dewlap, and historic references probably would have mentioned it if it was an obvious trait. But they do not, and all artistic depictions, including cave paintings, show short dewlaps. Most likely the dewlap of European aurochs was about as short as in cold-adapted taurine cattle (yakut cattle, Highland cattle, Heck cattle at the Oostvaardersplassen). It is possible that it was even shorter, but we cannot know because of the absence of soft tissue aurochs mummies (there was, actually, a complete skin of an aurochs found in Germany at the beginning of the 20th century, but its soft tissue has not been preserved [Frisch, 2010]; there might be more cases like that).
Winter fur length
The aurochs most certainly had a bi-layered winter fur. The undercoat was likely short and dense, but the question is how long the outer coat was. Surely the length and density of the winter coat was dictated by the requirements given by the climate, so it was dependent on region. I have been wondering about the winter fur of central and northern European aurochs. Since there are no preserved aurochs skins, we can only guess how long the winter fur of these kind of aurochs actually was – what was the minimum, what was the maximum of what is physiologically useful and what was the actual case?
Schneeberger states that the aurochs was covered in longer fur than domestic cattle, but does not clarify whether this was generally the case or during a specific season, and what kind of domestic cattle he was thinking of is unclear either (hardy landraces do have a more efficient insulating coat than more derived cattle). Looking at hardy taurine landraces that are adapted to living outside all year round in temperate climate could provide an useful aurochs analogue. HungarianGrey cattle and Heck cattle sometimes grow a comparably long (but still not as overlong as in Highland cattle) woolly winter fur that gives them a shaggy appearance. In my subjective, google-based perception this is particularly apparent in some individuals from the Oostvaardersplassen, but I might be wrong. Many Grey and Heck cattle however have a winter fur that is a little shorter and similar to that of Betizu and Yakutian cattle, two breeds which are good models as well – the former having a feral history, the latter being well-adapted to harsh cold. However, Chianina have a comparably short winter coat yet they still do just as well in central European winters as do Heck cattle and Sayaguesa living in the same area. So was the aurochs’ winter coat minimalistic and as long as in Chianina, was it long and woolly as in some Heck and Grey cattle individuals or somewhere in between like in the majority of Heck cattle, Betizu, Yakutian cattle and other landraces? Size could be a factor: a large animal has, in relation to its size, lesser heat loss than a smaller one of the same morphology. Therefore a 180cm tall aurochs bull might not need a winter fur as long and shaggy as a 140cm tall Oostvaardersplassen Heck bull (I am not saying that this is the reason why Chianina have a comparably short winter coat, I consider that a coincidence that is the result of how Chianina have been husbanded as a breed). But it is questionable how influential that factor really is here, especially because domestic cattle and aurochs even at that height difference might still have a similar mass due to their different morphology. Another factor is the ability to store fat, which contributes to insulation as well and therefore influences the need for an insulating coat.
While it would be nice to know how long and shaggy the winter coat of central- and northern European aurochs was exactly, I think it is not something that breeding projects have to worry about in particular, as long as the animals do well during winter and seem to be fit for survival under natural circumstances.
The colour of the dorsal stripe
The immediate answer you get is “light-coloured”. But extant wildtype coloured cattle actually display dorsal stripes of various colour shades, ranging from yellowish-white over yellowish-red, golden, shiny red to brown. The English translation of Schneeberger’s report in Gesner 1602 says the dorsal stripe was of a lighter colour as translated in van Vuure 2005, originally it says “subnigra” in Latin. This is a bit imprecise but must have meant some kind of grey. Sigismund von Herberstein was in possession of an aurochs skin, and termed colour of the dorsal stripe “grahlat”, what is to be translated with grey. More precisely, this grey colour was the result of white hairs mixing with the black hairs that covered the rest of the body. The only cattle having a grey eel stripe without any shades of red or yellow are those that display a diluted coat colour, such as Podolian cattle. Contemporaneous artworks give no useful clue on the colour of the dorsal stripe; some of paintings at Lauscaux and Chauvet cave implicate that it was there, but do not point to a specific colour.
This opens the following questions: did all wild aurochs have a dorsal stripe of the same colour or colour variation spectrum, and was it as wide as in wildtype coloured domestic cattle? Or were wild aurochs, at least the central-northern European ones, different in having a greyish eel stripe without having diluted colour shades at the same time? It might also be the case that, assuming the colour of Herberstein’s skin was not artificial (due to damaging or discolouring), the dorsal stripe in that individual was simply reduced, perhaps due to aging. I have been playing with the thought that not all wild aurochs always had a visible dorsal stripe for quite some time, in the same way the extent of the muzzle ring in gaurs and banteng is variable. But the question is, was Herberstein’s individual an exception, or representative for the rule? And if the latter was the case, was this true for all wild aurochs or just the central-northern European group?
Because of these uncertainties, I don’t stick to a certain colour shade for the eel stripe, because evidence is simply not compelling enough neither as the rule for central-northern European aurochs nor all wild aurochs. Intuitively I think that the aurochs, at least the African, Near Eastern, Asian and probably also the southern European populations, might well have displayed the diversity of colour shades for the eel stripe that domestic cattle with an un-diluted, wildtype colour do. If I had to pick only one colour for the dorsal stripe of a central-northern European male aurochs, I would take a very pale, greyish one because of the literature references – but other colours might do it just as well.
Width of the dorsal stripe
The dorsal stripe is usually described as “narrow”. To be exact, Schneeberger stated it was “about two fingers wide”, therefore a few centimetres. Von Herberstein, who owned an aurochs hide, made no mention of the width of the stripe. The “two fingers wide” condition is most common among wildtype coloured domestic cattle. However, in some cases, the eel stripe is rather broad, such as in some Lidia, Maronesa or Heck bulls. In these individuals the anterior end of the stripe is V-shaped, meaning it starts rather broad at the shoulder area (this area is usually where the dorsal stripe is widest, it is narrowest in the lumbar region or at its posterior end). The opposite is the case as well. There are bulls which have a rather narrow, reduced eel stripe, for example some Sayaguesa or, again, Lidia bulls.
Due to the scarcity of data, we do not know whether there was variation in the width of the dorsal stripe or not, and if that variation was as big as in domestic cattle or less.
The colour of the forelocks
This is a question that has been puzzling me for years now. We know from historic references and also artworks (heraldry, Smith’s painting) that the European aurochs had frizzy, curly forelocks that we also see in many taurine cattle. In wildtype coloured domestic cattle, these forelocks (or more precisely, the area between the horns on the front head) show a colour that ranges from light blond over orange-reddish, reddish-brown, dark brown to completely black as the rest of the facial hair. Cis van Vuure considers lightly coloured forelocks in bulls a discolouration that occurred after domestication (in wildtype coloured cows, a lighter coloured area between the horns is a standard feature and also supported by a cave painting in Lascaux). Written contemporaneous accounts suggest that this area was coloured just like the rest of the face: Schneeberger mentions the eel stripe, so he might have mentioned a special colour of the forelocks as well if there was one (however, he did not mention the muzzle ring either, although cave painting suggest its presence in wild European aurochs). Von Herberstein was in possession of two belts made from aurochs forelocks, and the colour of these forelocks was supposedly black based on his descriptions. North African engravings showing the African subspecies depict bulls with a light colour saddle on its back, in at least one case even the light muzzle ring (see Frisch 2010; I am not referring to those tomb paintings that most likely show domestic cattle described in van Vuure 2005). Again, if these bulls had forelocks of a special colour, they might have drawn them just as the colour saddle and muzzle ring. Furthermore, the aurochs, or at least black bulls, are popular symbols in heraldry all over Europe, but not a single emblem shows a bull with lightly coloured forelocks.
Furthermore, lightly coloured forelocks might correlate with a reduced sexual dichromatism or at least a reduction of melanisation. Light forelocks often correlate with a colour saddle in bulls, f.e. in less melanised breeds such as Alistana-Sanabresa and Cachena, while blond forelocks are never to be found in a dark breed such as Sayaguesa. All cases of bulls with a colour saddle that I have seen so far show lightly coloured forelocks, whereas in Maronesa, one of the few breeds with a well marked sexual dimorphism, most bulls have either black or dark forelocks, and never a saddle. Also Heck lineages with an (by the breed’s standard) acceptable dichromatism show bulls with mostly black or dark forelocks (I am thinking of the herds at Hellabrunn, Tierpark Haag, the Neandertal and former Wörth herd), with some exceptions. There are a number of Lidia bulls that show blond forelocks, and Lidia is, just like Heck cattle, heterogeneous also in terms of sexual dichromatism.
Gaurs and Banteng also a have lighter coloured area between the horns. In the Java Banteng, which is the extant bovini with the most strongly marked sexual dichromatism, the light area is not part of the coat colour, but actually a keratinized area. The gaur has a very reduced sexual dimorphism – but not completely absent, you can still see that cows usually tend do be not quite as dark and blackish as the bulls are. Both sexes have lightly coloured hair between the horns. One could argue now that having a light area between the horns therefore is a plesiomorphic condition that the wild ancestors of taurine and zebuine cattle must have had as well. But this must not necessarily be the case; white muzzles, or eye rings as much as dorsal stripes are all characters that originated multiple times but perhaps have the same underlying genetic mechanisms (note however that the dorsal stripe in horses and bovines are different).
While it is just a speculation that lightly coloured forelocks in bulls are the result of reduced sexual dimorphism, evidence does not support this trait for wild aurochs bulls. All sources suggest that the forelocks of the aurochs were of a dark or black colour, so van Vuure might well be right with considering lightly coloured forelocks a discolouration that occurred after domestication. But the data is in my opinion not comprehensive and precise enough to rule out this trait for wild aurochs, due to the uncertainty it should also not be bred against in breeding projects.
But if I had to pick only one colour for the restoration of the forelocks of a wild European bull, I would take black or dark forelocks, which is the colour I usually use.
Some of you might already be familiar with my idea that at least the European aurochs had a kind of “mane” additionally to the frizzy, curly forelocks between the horns because of a post in 2015. By “mane” I do not mean an opulent mass of hair such as bison have, but rather just curly, perhaps only slightly longer, hair on the head, neck and perhaps also shoulder area. This trait would be present in bulls only, while curly forelocks can be present in both sexes. Actually a lot of domestic bulls show such a “mane”, though to a variable extent. I came up with the idea that it might be a functional aurochs trait when I read that this “mane” (which is also where I got the name for it from) is suspected to protect a Chillingham bulls’ skin during fight from the horns of the opponent, because these areas are the most exposed during such a combat. Then I noticed that a number of Oostvaardersplassen bulls actually have this kind of mane too, while I have seen barely one such a case for Heck cattle outside the OVP. So this might suggest that there is some kind of selective advantage for this trait, although it is only speculative. Lidia is another example for a breed were we find some bulls with a prominent “mane”.
Curly hair is a typical bull feature, and the mane was not necessarily that eye-catching that historic witnesses must have mentioned it. That is also why I gave my aurochs bull model from 2014 curly hair on face, neck and throat, and I think I will do so again when doing my next aurochs model. However, only preserved aurochs skin, a notion in historic references or contemporaneous artistic impressions can proof if some bull aurochs had such a mane. The various spots on neck and face of two of the Lascaux bulls (the line drawings) might indicate such curly hair, but that is only a guess of mine.
Aureole around the eye
Ocular aureoles, a white ring around the eye, are common in all kinds of ruminants. It is also common in Bos. One subspecies of Banteng, Bos javanicus birmanicus, have them on regular basis, other subspecies of Banteng and also gaurs have them on occasion. Aureoles are a common trait in domestic cattle as well, at least those having wildtype colour expressed. It is a trait often shown by calves that disappears later on, but there are many grown cows that show this trait. Grown bulls usually do not, except for breeds and types of cattle that are rather small and/or display a number of neotenic features, such as Cachena and (miniature) zebu. Aureoles in grown individuals do not correlate with diluted colour variants, because cows with a colour rich of red pheomelanin can have these rings too.
This provokes the following questions: Were aureoles present in wild aurochs too? If so, was it a general trait or dependent on regional variation, and was it limited to one sex in adulthood?
Artistic depictions of aurochs do not suggest the presence of ocular aureoles. There is just one case, the painting of a black male aurochs at Lascaux, that shows a white ring around the eye. But it is unknown whether the artist really wanted to depict an eye ring or merely intended to implicate the presence of the eye. CharlesHamilton Smith’s aurochs painting has a slim white ring around the eye that might be interpreted as an aureole, but this is only a second-hand artwork based on an artwork itself. Apart from those two cases, no artistic representation of the aurochs indicates the presence of eye rings, neither do any historic references.
This and the fact that only bulls that otherwise display neotenic traits and very small size have eye rings as adults makes it unlikely to me that at least the European and African subspecies had such aureoles as grown males. But for cows, it seems like an open question to me whether at least some of them had them or not. I tend to think that grown European female aurochs usually did not have light eye rings, mainly because there is no mention of it and none of the artistic depictions show them (I am thinking of coloured cave paintings). In the end, we cannot know whether some wild aurochs cows (and also bulls) had this trait or not, and if it even was a general characteristic for certain populations or subspecies.
It turns out that even the white muzzle ring or mealy mouth is not that solidly supported by the data either. There are no written accounts for it that I know of. However, a number of cave paintings show it, or at least point to it, and also Smith’s aurochs shows a reduced one (OK, here goes the same as for the eye ring). But what is also striking is that it is a fixed, permanent trait of nearly all wildtype coloured cattle on this world; there are only a few exceptions where the muzzle ring is either strongly reduced or barely visible due to some modifiers, but basically it is always present in E+//E+ cattle. So it should have been in wild aurochs too. However, it could have been the case some individuals, especially bulls, that it was reduced or even very reduced when they aged, so that the white area might have been restricted to the upper lips and chin – the way we see it in a number of taurine bulls, Gaurs and Banteng. In such individuals, the “mealy mouth” would not have been such an obvious trait that it would be considered worth mentioning anymore. Perhaps such a reduced white muzzle was even the case in fully grown (European?) aurochs bulls. But that is speculation.
Colour shades in cows
This covers two aspects: the amount of eumelanisation (how much black is in the coat colour) and pheomelanisation (when is the colour so faint that it has to be considered a domestic dilution).
Wildtype coloured cows show a spectrum from almost uniformly light brown over darkening from head, neck and legs and subsequently the lateral side of the trunk until the whole body is dark brown/black except for a more or less large light colour saddle – if that saddle is absent, the cow is coloured like a bull should be.
So, which state in this continuum is the “correct” one, at least for European aurochs? We cannot say. Artistic depictions, even the Lascaux cave alone, support the whole spectrum. It shows, among more detailed figures, cows that are drawn uniformly brown, sometimes only as lines, which might either indicate that the individuals they are based on were of that uniformly brown colour or the artist did not intend to reproduce its colour more detailed. The will to represent the animals accurately is always a problem for artistic references; if someone, say, spotted a mufflon and drew or described it being just “brown”, he might consider that sufficient, although the coat colour of a mufflon is of course more facetted. That’s also the case with Schneeberger’s report, where the cows are simply said being of the colour of calves (“chestnut”, “blackish brown”, “dark brown” etc.). There are a number of Heck and Maronesa cows those colour is of a more or less uniformly dark chestnut brown colour, which might fit what Schneeberger had in mind.
Lascaux however also includes more defined representations of cow colours, such as very dark cows with a red colour saddle. And just as there are cow depictions completely lacking black, there is also one that is almost completely black with a very narrow colour saddle at Lascaux. This colour is perfectly represented by the Sayaguesa cow posted above (bottom row centre), or the Taurus cow at its left. Schneeberger also mentions that very rarely, black cows appeared. This notion is one of the reasons why black cows are usually tolerated in breeding projects. A bull-coloured female aurochs might have been either the result of the genetic diversity within the population, or of a twin birth. When a cow is the twin of a bull, it might get infertile and develop the colour of the male because it gets more male hormones than it should (I am not a developmental biologist, so please excuse me for this imprecise language). If Schneeberger was referring to results of such “accidents”, the legitimation for black cows that are the result of lessened sexual dichromatism in breeding-back herds would be gone. But in any case, I have always thought that in an ideal case the portion of bull-coloured cows in such a herd should not be larger than 5-10%.
Regarding all the non-bull-coloured shades that seemingly were present in the population, it is the question whether they were distributed equally in the population or if there was a prevalent type, if there was a regional gradient (the cave paintings are all from southern Europe, but not the same time; so they might represent aurochs of different genetic clusters). Artistic interpretations and written accounts are too scarce, regionally limited and not precise enough to be nailed down to one colour shade only, so that we can probably permit the full range for breeding, or at least can not rule out one particular type.
What is also striking is that there is a continuum from a rich, shiny red pheomelanin-caused portion in the coat colour and the leucistic, colour-less grey that results from the lack of pheomelanin. Alleles that cause these state are called “dilution factors”. But since there is a continuum in crossbreed populations at least, the question is: at which point are we dealing with the presence of a dilution factor and which colour shade is still wildtype?
Historic references as much as contemporaneous paintings all suggest shades like dark brown, reddish brown, chestnut, light brown, ashy for aurochs cows. There is no mention or depiction of beige tones or greyish tints, for example. The only way to tell the individuals apart that carry the probable wildtype homozygous would be to identify the modifier alleles that are responsible for the amount of pheomelanin in the coat, because we are most likely dealing with more than one locus and intermediate states, that should be the reason why we see a continuum.
Colour saddle in bulls
This is another aspect of the aurochs’ coat colouration that can be a matter of debate. Some argue that a light colour saddle in bulls was present or might have been present in (European) aurochs, at least that we cannot rule it out. I use to regard this trait as a sign of reduced sexual dimorphism just like a bull-coloured cow, and there are no written or artistic references that support the presence of a colour saddle in male European aurochs. On the contrary, most references describe the aurochs as a black or at least very dark animal – be it Plinius (“bos sylvestris niger”), the classification of the aurochs as “suarzwild” (“black game”, together with wild boar) in the Lex Baiuvariorum AD 800, a figure on the Carta Marina by Olaus Magnus (who probably saw living aurochs at Jaktorow), or von Herberstein, who held an aurochs skin in his hand and described it “entirely black” except the dorsal stripe as much as Schneeberger’s description and all cave paintings that both include only completely black bulls with the dorsal stripe.
So the body of evidence suggests that wild European bulls did not have a colour saddle, at least there is no reason to think otherwise.
However, as mentioned above, there are artistic depictions from Northern Africa that suggest at least the African subspecies had a colour saddle.
Of course it is harder to prove absence than it is to prove presence, but until there is some evidence that European aurochs bulls were not always completely black (except for the dorsal stripe and muzzle ring, and maybe forelocks), I assume that a colour saddle in a bull is indicative of reduced sexual dimorphism and something that should be avoided in breeding – at least for breeding bulls. So far, a saddle in bulls is permitted in all breeding-back projects and breeds. I think this is not effective for breeding bulls, but of course such a bull can still be desirable because of other traits, it is always about balancing traits.
As you see, a large part of these open questions or uncertainties concern coat colour, since the morphology of the aurochs is well-known thanks to the comprehensive bone material. I have also speculated that some colour types we see in domestic cattle might have evolved in the aurochs already, such as solid black all over the body (Ed allele) in wild B. primigenius primigenius, or it might have gotten transferred from domestic populations into wild ones, or that the dilution alleles that cause the greyish colour of many zebuine cattle as much as in Podolian cattle might be a wildtype trait of B. p. namadicus. There is no evidence pointing to that, these are just thoughts that I consider not totally implausible.
One could, just like a number of authors did it with horses, test aurochs bone material for coat colour alleles. As a test to see whether those alleles we consider wildtype were indeed present in the wildtype and to see whether unexpected variants, like Ed, were present or not in wild populations. It could also be used to rule out the proposal of a Chillingham cattle-like spotted pattern for predomestic aurochs (a suspicion that is based on line drawings from Lascaux – but I consider this evidence not compelling at all).
Since a number of cattle modifier loci and alleles are only speculative, some of them would have to be identified before looking for them in aurochs material. I am not that optimistic that such a study would be conducted in the near future however, since the interest in cattle and cattle coat colours is not nearly as big as the interest for horses. Nevertheless, the data gained from such a study could be helpful for breeding projects. For example, once all the dilution modifier alleles are identified, cattle from breeding projects could be tested for those. In this way, breeding bulls carrying recessive dilution alleles could be avoided.
A while ago, I illustrated what a Chillingham-coloured aurochs, solid black aurochs and my Indian aurochs bull with Agouti dilutions seen in Podolian cattle would look like. Again, I am neither proposing that aurochs of these colour variants existed nor am I “believing” it, I am just illustrating possibilities.
Walter Frisch: Der Auerochs: Das europäische Rind. 2010.
Cis van Vuure: Retracing the Aurochs - History, Morphology and Ecology of an extinct wild Ox. 2005