Colour saddles in bulls: good, bad or neutral?

The life appearance of living European aurochs is pretty well resolved. We have numerous well-preserved bone material, related species and descendants to compare with, and contemporaneous references in art and literature that provide us a clue on what the European aurochs looked like. However, it is not as precise as if someone would have taken coloured photographs or made taxidermies of a sufficient number of individuals back the time when they were still around and well, and therefore not all aspects of its external appearance are known with certainty, or the degree of regional and individual variation of traits that are not indicated by the bones. I made a post about traits where we have no certain clues for, such as the colour of the forelocks in bulls and if there was variation, or which colour shade was prevalent in cows.

Two further questions rise up in “breeding-back” concerning the colour of the bulls. Where there European aurochs bulls that showed a so-called colour saddle? And if not, should we still permit it in “breeding-back” bulls, especially breeding bulls?

At first I want to explain what a colour saddle is. In wild-type coloured cattle (phenotypically E⁺), both sexes are born with a chestnut-brown colour and eumelanisation (eumelanin is the black pigment, pheomelanin the red pigment) with black pigment starts from the head, neck, feat, pelvis and tail tip. The degree of eumelanisation is dependent on testosterone level (and, I hypothesize, perhaps also other signal molecules). In wildtype coloured cattle displaying sexual dichromatism, the melanisation of cows stops earlier than in bulls, leaving them lighter coloured. The “standard” aurochs bull colour that is suggested by the evidence involves full eumelanisation of the coat of the bulls with the exception of the muzzle ring and dorsal stripe (of course in domestic cattle, where selective breeding greatly altered the phenotypic traits and sexual dimorphism, you find a lot of  “bull-coloured cows” and “cow-coloured bulls”). In cases where the melanisation does not run until this maximum point but stops earlier, a light area on the dorsal and – depending on degree – also pelvic area remains. This is called a colour saddle. You find that in many wildtype coloured cows and bulls. For cows, it is universally desired. For bulls, there are diverging opinions. The photos down below show a fully melanised wildtype coloured bull (Churro, a Sayaguesa bull, photo by Matthias Scharf) and a wildtype coloured bull with a saddle (its son Linnet, a Taurus bull, photo taken by myself).

Margret Bunzel-Drüke from the ABU also pointed me to the possibility that a saddle in bulls might just be a very broad dorsal stripe, but I have to say I am not convinced of that. Colour saddles are usually not that sharp-edged, and usually show some sort of colour gradient. Dorsal stripes, on the other hand, are always sharp-edged and the colour is more or less homogeneous. And more importantly, even in the colour saddle itself you can usually discern the dorsal stripe, unless the colour of the saddle is very light.

Now I am going to have a look at the questions above.

Where colour saddles present in wild European aurochs bulls? When we discussed about bulls with colour saddles this year, Margret Bunzel-Drüke told me that the colour variant we want in “breeding-back” is called “castania” by Spanish breeders (and considered wildtype by us), and therefore cattle displaying this variant should simply display the colour of the aurochs. This is also the same case in horses, dogs, cats and budgerigars – when the genes are the same, they display the colour of their wildtype. However, there is a difference in the case of cattle. Not only the colour genes themselves determine what the final colour will be, but as outlined above, it is also dependent on the level of at least one signal molecule – testosterone – and therefore linked to sexual dimorphism. As an example, I think it is pretty plausible that Sayaguesa and Cachena have the same colour alleles (wildtype+ on each loci as I see no divergent colours). In both breeds, the sexual dichromatism is very reduced, Cachena being on the less eumelanised end of the spectrum, and Sayaguesa obviously on the strongly eumelanized end of the spectrum.

As a consequence, the question is not just which colour alleles were present in the aurochs but also how strongly marked the sexual dichromatism was in the case of the aurochs. For that, we have to look at the historical evidence we have.

Cis van Vuure, who intensively studied tons of contemporaneous literature and artworks featuring aurochs, is convinced that European aurochs bulls at least did not have a colour saddle. The famous cave paintings (Lauscaux, Chauvet et cetera) give us a clue about the colour of living aurochs at that region and time (Pleistocene, Southern Europe). They show aurochs cows of really all colour shades we find in living wildtype coloured cows, also a “bull coloured” one, but the bulls are shown always black. There are also some line drawings of bulls, but a saddle is not indicated (yet there are some small spots on the head and neck area – I assume these are meant to indicate curly hair but there are also other possibilities). Anton Schneeberger, who delivered the most precise verbal description of living aurochs in Gesner 1602, described the bulls being completely black except for the light dorsal stripe, and cows being of a chestnut colour, and only very rarely turning black as well. In the Holy Roman Empire of the Middle Ages, hunters categorized the aurochs as part of the “Schwarzwild”. In German, hunters like to categorize game after their colours (roughly): “Schwarzwild” means “black game”, and nowadays only includes wild boar as the aurochs died out 400 years ago. “Rotwild”, meaning “red game”, is a hunter’s term for Red deer. So it seems that a black or very dark colour must have been prevalent in the perception of an aurochs for the contemporaneous people (this, of course, neglects lightly-coloured cows; bulls probably got more intention as they made way more impressive trophies). The Carta Marina by Olaus Magnus shows a rider being attacked by a dark brown aurochs, from the year 1539. However, the drawing is very stylized. Sigismund von Herberstein was in possession of a stuffed aurochs coat, and it showed a black colour with a faint dorsal stripe. Plinius quotes an earlier source that describes the aurochs as the “black forest ox”. Romanian folk tales also speak of the “black aurochs”. Russian and Polish stories and expressions, however, speak of red or reddish brown aurochs. But it is unclear in these cases which sex is to be meant. The social system of cattle includes cow herds with calves and young bulls, where the prevalent colour would be reddish-brown, and solitary bulls. If one witnesses a cow-calf herd, he would most likely describe “the aurochs” as reddish brown. If one witnesses a lone bull, it would depend on the colour of the individual bull. For the references of these historical accounts, see van Vuure 2005.

So what to make of this? It is not only that there is no evidence for colour saddles in bulls. It is interesting that Schneeberger notes the presence of such a minor detail as the narrow dorsal stripe, but not a colour saddle. If some of the bulls he witnessed had one he might have mentioned it as well, especially since he mentions the very rare black cows. One could criticize that he does not mention the muzzle ring as well yet it is considered a universal trait of the aurochs, but old bulls often have a very reduced muzzle ring (see Churro) and perhaps not all aurochs had this trait; Bantengs and Gaurs are variable in this respect as well.

Even more interesting is that at least two North African prehistoric stone carvings that I am aware of show aurochs bulls being hunted (I am not confusing them with the tomb paintings that show domestic cattle) that definitely have an extensive colour saddle (one of them also shows the muzzle ring). These are line drawings and the saddle is indicated. Is it a coincidence that for Europe, although there are many artistic and written references to the colour of aurochs bulls, there is no evidence for a colour saddle and in North Africa at least in two cases? Of course this is possible, and we have no direct way to prove that, but I think not. I consider it more likely to say that European aurochs bulls probably lacked a colour saddle while the African subspecies either showed it on occasion or universally. Would not a shiny red colour saddle extending on the whole back of the bull be a rather prominent trait that is worth mentioning? And if there were indeed European aurochs bulls with such a trait, why do all the sources always support black bulls only (in the cases where bulls are definitely referred to)? Apart from that, the contrast between the reddish-brown saddle and the black surrounding colour was that striking that eyewitnesses would have barely simply described such an individual as being of a “brown”, “black” or whatever colour but probably refer to the saddle in particular (would you when taking a look at a bull like Linnet on the photo above?).

So it seems more likely that European aurochs bulls never, or in very rare cases (twin births, after injuries of the gonads) ever had a saddle and that they were universally black, while there were black cows on occasion.

Should we permit bulls with a saddle for breeding then? Currently, all “breeding-back” projects permit a colour saddle in bulls more or less. I have always been against the use of bulls with a colour saddle as breeding bulls because of the risk of reducing the sexual dimorphism of the herd. In a previous post, I outlined that always picking black bulls and red cows for breeding probably will not result in the strongly marked sexual dimorphism of the European aurochs because one would have to consciously pick those individuals where sexual dimorphism is actually laid down in the genome. A black bull might just as well inherit black or very dark cows. Without knowing the exact genetic background of sexual dichromatism in cattle and without screening each individual for it, we can never know whether a black bull or a red cow inherit the sexual dichromatism we want. In the case of a bull with a saddle, however, we can be sure that the sexual dichromatism is reduced and since the sexual dichromatism is already less than in the aurochs, using such an individual for breeding might reduce it even further (the same goes for black cows of course, but black cows are confirmed to have existed in Europe while bulls with saddle probably did not). There is one possible example for that in the Lippeaue.

In the Hellinghauser Mersch herd, the Sayaguesa x (Heck x Chianina) bull 42 623 is currently used as a breeding bull. This bull has a colour saddle but does not display any colour dilutions. Some of its male offspring show a colour saddle as well, and I got the impression that they do that more often than the offspring of the black bull Lamarck. One of the young bulls I spotted in the field has a rather extensive saddle, or actually it is a brown back that gives it the colour of a cow. Using this individual for breeding might probably result in a number of wholly reddish-brown bulls appearing in the next generation. I would definitely not recommend using a bull with saddle or brown back for breeding if it itself descents from another bull that had a saddle as well. It might make this trait even more common in the population and lower the variation span towards more brownish bulls.

Nevertheless, the degree of sexual dichromatism is just one of many traits that “breeding-back” focuses on. Of the five breeding bulls at the Lippeaue, two have a colour saddle, but both of them are valuable for breeding. Linnet has a good horn curvature that shows the desired inwards-curve and 42 623 is a 170cm giant with a prominent shoulder hump. So the colour saddle can be permitted as both bulls contribute precious traits to the herds. It is like the fact that too small horns or such of insufficient curvature are not desired, but a bull might contribute other desired traits that are otherwise rare in a population, so that this deficit can be connived and corrected in later generations. There are also varying degrees of a colour saddle. For example, a saddle can either be very small or very faint (such as in the Taurus bull Luxus, which was used as a breeding bull for a short time about ten years ago). Also, subadult bulls might show a saddle but outgrow it as they age, such as Manolo Uno, the most famous Tauros bull to date. However, I would not use a saddled bull that itself descends from such a bull, as there is the danger of perpetuating this trait.

So a bull with a colour saddle does not always have to be selected out, but I recommend to avoid this trait for breeding bulls unless it has a number of otherwise valuable traits.

Literature 

Cis van Vuure: Retracing the aurochs: history, morphology and ecology of an extinct wild ox. Pensoft, 2005.