The horns of the Aurochs

The aurochs is often remarked for its impressive horns, which were larger than those of most domestic cattle. Contrary to some other claims, the horns of the aurochs were – just like those of other wild cattle – more or less uniform so there are clear objectives that breeding-back should focus on.

Curvature

Some authors compare the curvature of the aurochs’ horns to a spiral, which they call the “primigenius spiral” [1]. Because this is a useful term, I’ll continue to use it when referring to their characteristic shape here, which consists of a curve going outwards and upwards at the base, then curving downwards again, forwards and inwards, and finally inwards and upwards at the tip.

Image by Miguel Omar Ruiz Hernandez showing the 3-dimensional shape of the aurochs horn

The base was the thickest part of the horns and the tip usually ended slim and pointy, what surely was intensified by the keratinous horn sheath in life.

There are a lot, possibly hundreds, of preserved bony aurochs horn cores found in- and outside Europe. This amount of material tells us that the primigenius spiral shape was always present [1], but there was variation in the way the horns exactly showed that curve. Some individuals had more wide-ranging horns, such as a skull displayed in Stuttgart, while others had very inwards-facing ones, such as the bull from Prejlerup. 

Pleistocene skull with wide-ranging horns found, Stuttgart (Photo: ©Markus Bühler)

Life reconstruction of the Prejlerup bull, Denmark, with very inwards-curving horns. All rights reserved. 

One aurochs might have had comparably slim horns while another one had very thick ones. Also the angle in which the horns were attached to the skull varied. According to Cis van Vuure 2005, the angle varied between 50° and 70° and also other authors found 60° to be the arithmetic mean. However, I have seen photos of skulls which show an angle either larger (Vig) than 70° so the total scope might be slightly larger.

Bull skull from Italy with sharp angle between snout and horns

Bull skull from Vig (Denmark) with more upright horns

The position of the horns relative to the skull changes the way how the horns look in frontal view. The larger the angle to the snout is, the more < > -shaped the horns appear (I don’t have word for that, some call it “lyre shaped”, but a lyre looks more like the horns of Steppe cows to me). The lower the angle is, the more the horns look like that of good Maronesa or Lidia bulls. My aurochs horn model, made from DAS clay and painted with acrylics, photographed from different angles, illustrates that very well.

For anyone interested, the model measures 78 cm in length and has a circumference of 40 cm at the base.

Reconstruction of a lost skull from Berlin. All rights reserved.

Size

According to Cis van Vuure, the smallest and largest horn diameters at the base are 7 and 18 cm, the smallest and largest length 40 and 107 cm. These measurements were obtained from bony cores, so we have to consider the keratinous sheath, which adds about 10-20 cm in length [1] and 8% (therefore a few centimetres) to the circumference at the base [2]. A large Pleistocene skull that was found at Mannheim, Germany, had horn cores with a length of 93 cm and a horn span (from the outermost point of one horn to the other) of 123. Large skulls like these are no exceptions, the probably largest known aurochs skull is exhibited at the British Museum, London, and measures incredible 91,2 cm in profile. Surely this must have been a huge bovine. Other Pleistocene samples from Italy, which was a refuge for aurochs and other mammals of the interglacial fauna during the Würm glacial, show aurochs of very large size as well. Some horns of the Chiana Valley have a circumference of ~43 cm, the largest specimen are known from an area near to Rome, which had a length from 69,2 to unbelievable 120 cm (still without keratin) [2]. The horns of the Indian aurochs where about the same size, but since the B. p. namadicus was slightly smaller overall than B. p. primigenius, they were proportionally larger. With the end of the ice age the horns of the aurochs tended to be less huge and wide-ranging [2,3], but were still impressive. This reduction of size is probably connected to the disappearance of large feline predators, and the same happened to Bison as well after Panthera leo atrox died out, when you compare the horn dimensions of Bison priscus with those of extant B. bison. However, aurochs still had to deal with wolves in the Near and Middle east and North Africa.

Ridiculously huge pleistocene horns, found in Germany. 

Very large skull on display at Lodon. Photo © Marie Griggs

Sexual dimorphism

The horns of the aurochs are said to display a clear sexual dimorphism [1,2,3]. Usually the horns are described as being larger than those of the cows, which sounds plausible (but read on). Of the skulls I had a look on (and I know really a lot of photos of aurochs skulls), cows seem to have more wide-ranging, more upright and less strongly curved horns than the bulls. A considerable size difference is not really apparent for me, but I trust the experts. In domestic cattle, the bulls usually have more forwards-pointing horns while those of the cows are longer but thinner – how can that be? First of all, who knows how much keratin plays a role here. Furthermore, it is not always easy to determine the sex only from fragmentary skeletons, and there were probably exceptions regarding the horns within one sex of the aurochs as well. The Vig specimen for example, which is thought to be a male because of its large size and massive bones, has very female horns (they appear female in being very upright by aurochs standards, thin and do not curve inwards very strongly). What is strange is that in domestic cattle of the same breed the horns of the bulls are usually straighter and more outwards than in cows, you can see that in a number of breeds (Sayaguesa or Heck, for example).

Horn sheaths

A number of keratinous horn sheaths still exist; their either survived in turf or as ornamented (drinking) horns which where owned by the European nobility. One of the best-preserved and best-known aurochs horn sheaths is that of the last aurochs bull which died in 1620, which is now kept at the armoury of Stockholm. It shows the least discolouration because it is the youngest, and also is very slim compared other horn sheaths of the middle ages or older bony cores, what probably shows that the last aurochs at Jaktorow, Poland, had slightly diminished horns due to their limited range and trophy hunting [2]. The same is also known from elks but I have no reference for that at hand at the moment. The Danish national museum also has an impressive collection of a number of ornamented aurochs horn sheaths. Most of them are discoloured.

Horn of the last living aurochs bull which died in 1620 at Jaktorow

Another horn which shows only slight discolouration and mightier dimensions than the one from Jaktorow is displayed at Brussels. When looking at the photos of all those beautiful sheaths you’ll see that the base is rather massive and the tip is very slim  (consider that most of the ornamented horn tips have their horn tips cut off), more so than in the bony cores. This tells you that the sheath adds pretty much to the length of the complete horn. The photos of some horn sheaths give you the impression that the horns have a rather two-dimensional crescent-shape, instead of the classic three-dimensional horn shape of the aurochs. This might be just an optic effect of the photo, or can be explained by the fact that both their tips and bases are cut in order to attach the ornamentation.

Horn sheaths at Servaasbasiliek, Netherlands

Compared to other wild bovines

The horn curvature of the aurochs is said to be characteristic for the species, probably because most domestic cattle lost it. But is it really an apomorphy, which is a derived state which characterises the species or group you are looking at, or is it a plesiomorphy, which means that it is inherited from its ancestors? The easiest way to solve such a question is to look at close relatives of the aurochs.

At first glance, the horns of Bantengs and Gaurs do not resemble those of the aurochs; they are very vertical and the only similarity seems to be the well-pronounced inwards-curve. But taking a closer look, especially on moving pictures, shows that they actually do have the primigenius spiral, just less strongly expressed. The same is also true of the horns of many wisents. The photo below shows an individual with particularly aurochs-like horns that I photographed at the Hellabrunn Zoo at Munich. The males of the probably extinct Kouprey had horns that resemble the aurochs closely, the most obvious difference being only bristles at the tips and wrinkles at the base. But the biggest similarity in terms of horns we can find in wild yaks – some individuals have horns that are virtually indistinguishable from those of the aurochs.

Yak skull with horn curvature identical to that of the aurochs

Wisent with aurochs-like horn curvature at Zoo Hellabrunn, Munich

This tells us that the horns of the aurochs are clearly not a defining character, an apomorphy, of the species Bos primigenius. The fact that closely related species display the same horn curvature implies that their common ancestor, the ancestor of both Bos and Bison, must have had the same horn curvature. This holy concept of parsimony in my opinion also rules out Bos acutifrons as a possible aurochs ancestor because it had very long and wide-ranging horns, unlike all other extant Bos members.

In modern cattle

As I wrote above, most domestic cattle did not retain the horn characteristics of the aurochs over the millennia of domestication. Therefore the horns distinguish the wild type from the domestic type very well, and it’s important for breeding-back to achieve “good” aurochs-like horns – not only for our satisfaction, but also because horns play an important role in the life of wild cattle.

Is there any breed that has horns identical or nearly identical with those of the aurochs? To answer that question properly, horn size and horn shape, consisting of curvature and orientation relative to the skull, should be viewed separately.

Horn size

Domestication tended to reduce the horn size of cattle. Only few cattle breeds, which mostly were artificially selected for horn size like Texas Longhorn, Barrosa/Cachena, Watussi and some Heck cattle have horns the size of what we see in large-horned aurochs. Steppe-type cattle like Maremmana, Boskarin and Hungarian gray also have horns matching the size of those of the aurochs, especially in length. Some Maremmana primitivo bulls display very thick horns. Highlands have the right horn length, but their horns are mostly – with some exceptions – rather thin. The horns of Maronesa also fit into the aurochs horn size range, but a bit more on the smaller than on the larger end I would say. Most Maronesa cows also have considerably thinner horns than in the aurochs.

Maremmana bull

Cachena cow

Curvature

Dairy cow in Brazil with perfectly aurochs-like horn curvature

Surprisingly, a number of derived dairy and milk breeds occasionally show horns with a virtually perfect aurochs curvature, which was also recognized by Cis van Vuure [1]. With some exceptions, like the Eringer breed, these horn shapes are never fixed and found only in single individuals. Of the primitive breeds, many Maronesa bulls and also some cows show horns with a curvature almost identical to that of many aurochs skulls, although the orientation relative to the skull is smaller in Maronesa on average. In many cows however, the horn tips face too much outwards, in some individuals to such an extent that they look corkscrew-like. The same is true for the related breed Barrosa, where the horns of cows are quite vertical but some bulls of this breed have a very aurochs-like curvature. 

Maronesa bull with perfectly aurochs-like horns, albeit oriented slightly too low

Barrosa bull with aurochs-like horns

The Spanish fighting cattle have horns of variable curvature, and some of them display a very good resemblance to those of the aurochs. Many other Iberian breeds have horns which curve in an aurochs-like manner but show some more or less clear differences. For example, outwards-curving horn tips in cows are quite common, but that does not rule out that some single individuals of breeds like Sayaguesa show decently inwards-curving horns.

As portrayed in a previous post, single Highland cattle individuals show a very aurochs-like horn curvature. The range of horn curvatures we see in Heck cattle are extremely variable too, and in improved lineages the Wörth lineage or Taurus cattle we see individuals with horn curvatures resembling the aurochs very closely as well, although in the former the horns tend to face too much outwards and the latter needs more inwards-curving horn tips as well. Even some Watussi cattle display horn shapes reminiscent of the aurochs, although often curving not strongly inwards enough and being to upright.

Sayaguesa cow with horns facing inwards

Taking both horn size and curvature, the number of breeds which fit the bill gets considerably smaller. Actually there is no breed in which the horns always fit the aurochs both in size and curvature. Some primitive Barrosa bulls come very close in absolute dimensions and curvature, the same goes for primitive Maronesa bulls albeit the horns are oriented lower in this breed than in the aurochs. The horns of most of the cows however do not resemble the aurochs that much; in female Barrosa they tend to be more upwards and lyre-shaped, while in Maronesa the often show a thinner, corkscrew-like shape and are considerably lower than in aurochs cows.

Wörth Heck cow "Erni" with slightly oversized horns (in relation to the animal) which are perfect in absolute size and curvature

The overwhelming majority of Heck cattle of this world have horns far from being identical with those of the aurochs. Yet there are a few individuals of improved lineages that have horns that resemble their wild type very closely. My favourite example is the cow Erni of the Wörth breeding lineage. Surely her horns are slightly too large in relation to the animal, but the absolute dimensions are absolutely authentic. I saw that cow in real and her horns give a lively impression of what an impressive animal the aurochs was. Apart from that, the curvature of the horns are absolutely correct. The Wörth lineage has some more examples of correctly aurochs-like horns, but they are not stabilized even in this lineage.

Literature

[1] van Vuure, Cis: Retracing the Aurochs - History, Morphology and Ecology of an extinct wild Ox. 2005.

[3] Frisch, Walter: Der Auerochs – das europäische Rind. 2010.

[3] Hans-Peter Uerpmann: Der Rückzucht-Auerochse und sein ausgestorbenes Vorbild. Neandertal Museum 1999.