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Friday, 30 August 2013

How big was the Aurochs really?


Size is one of the most important biological aspects of an organism. Therefore, an accurate substitute for the aurochs should also match the bodily dimensions of wild aurochs, apart from all the other features. In the past a lot of over- and underestimations on the true size of the aurochs have been made, so let’s have a look at how large the aurochs really was, and in which way its size was variable. Note that when I speak of size, I refer to the height at the withers and not the weight.

In the past the size of the aurochs has been broadly exaggerated, some authors suggested huge heights such as 230 cm at the shoulders, which lack supporting skeletal data and therefore are baseless. Also the hypothesis of an alleged “dwarf aurochs” on the mainland has been discarded long ago, since it was based on a misinterpretation of the large size difference between female and male aurochs [1]. On Sicily, however, aurochs which became isolated because of the rising sea level after the Pleistocene seemingly were 20% smaller than on the mainland [1].

Since no living aurochs were measured by contemporaneous people, we can only rely on skeletal remains for reconstructing the average size. Using single elements to extrapolate the withers height of the living animal can be problematic (usually the metapodials are used for this purpose), but the humerus was shown to be a somewhat useful tool for this [1]. Without doubt, near-complete, articulated skeletons are the best way to infer the shoulder height of the living animal, but there also are several problems that I’ll discuss later on.  

The data provided by various authors concerning the size of aurochs specimen are very variable, also depending on the respective period and region of the skeletal material. Especially the data given for bulls is very diverse, ranging from 145 cm to 200 cm [1]. Cis van Vuure summed up all credible measurements of aurochs shoulder heights and concluded that the average for Holocene aurochs bulls was 160-180 cm and cows 150 cm. The Indian aurochs seemingly was smaller than the Eurasian subspecies, and Eurasian aurochs during the Pleistocene were larger on average [1]. This size certainly makes the aurochs an impressive animal and significantly larger than domestic cattle, but related members of Bos and Bison are of a similar size.
Some authors suggested a dramatic and continuous size drop during the Holocene, making the last existing aurochs about the size of domestic cattle [2]. It seems, however, that the difference between Pleistocene and Holocene aurochs has been exaggerated, mostly because the Pleistocene specimen show considerably larger horns on average. Cis van Vuure estimates that the size difference between Pleistocene and Holocene aurochs might have been about 10 cm in both sexes on average, and indeed there are several Holocene aurochs specimen that exceeded a height of 170 and 180 cm [5]. In my opinion, a slight size decrease for Holocene primigenius members is plausible nevertheless, because of the absence of hyenas and big cats in Europe, what also offers an explanation why the horn size got reduced (the same trend is visible in American bison and their ancestors). However, we should not forget that aurochs belonging to other subspecies still shared their habitat with these predators in North Africa and India during the Holocene. In my opinion, the shift to a warmer climate at the beginning of the Holocene probably was not relevant for the observed size decrease, because the aurochs’ range retreated southwards during the glacials where the climate still suited the species, and spread northwards again when climate warmed again, so that the global climate change probably influenced only the occurrence of the species but did not force them to increase or decrease in size. Habitat disruption in historic times and hunting may have plaid a role [3]. But considering that the same also applied to the Wisent, which still measures about 180 cm at the withers in bulls, a dramatic drop in size for the historic aurochs seems unlikely to me and I don’t know of any data from actual bones of historic age supporting this. The claim that historic aurochs were just as big as modern domestic cattle seems definitely exaggerated to me, especially because historic references still describe the animal as being of impressive size and way taller than domestic cattle (even though cattle were smaller in previous millennia) [1]. Male specimens of a shoulder height not taller than 150 cm from historic times would be needed to verify this statement. 
Holocene southern aurochs remains usually show animals that are smaller than Northern aurochs specimens, what is accordant to Bergmann’s rule [1]. And interestingly, northern and southern Europe was seemingly inhabited by aurochs populations that were genetically distinct from each other. The Southern European aurochs belonged to the same genetic lineage as the near eastern populations, from which cattle were domesticated [4]. I suppose this lineage might have measured 150-160 cm at the shoulders in bulls, based on data [5] from Hungary. There are not many available measurements for the africanus subspecies, but it seemingly was as big as or a little smaller than the southern European aurochs [1].

My reconstruction of the Lund bull and the Cambridge cow.
Bull and cow are shown with a shoulder height of 170 and 146 cm, respectively (Human=180 cm).
All rights reserved.
 

This is as far as the skeletal remains go. But the problem is, skeletons often are mounted incorrectly, with their limbs bent too much and/or their shoulder blade in a wrong position, resulting in the skeleton appearing smaller than it really was. I once took a photo of a mounted bull skeleton from Braunschweig, Germany, and corrected its posture on the photo via GIMP. The skeleton in a corrected stance turned out to be 5% taller than the incorrect mount – what would increase a size of, for example, 165 cm to 173.25 cm. This shows that shoulder heights given from mounted skeletons have to be viewed with caution. Furthermore, we should not forget that mounted skeletons lack the connective tissue between the bones and the skin and flesh surrounding them, as well as the hooves. So we can add 5-10 cm to the height data from mounted skeletons to approach the size of the animals in life.
Something that seemingly isn’t considered by most of the authors referring to the aurochs’ size is the fact that most likely not all aurochs remains stem from fully grown individuals. The age of the actual specimen can be indicated by tooth wear, cranial sutures or the epiphysal plate. It is well possible that the smaller bull remains with a reconstructed height of only 145 or 150 cm were subadult individuals, therefore the ontogenetic age of the specimen should also be taken into account.
Numerous references give information on the observed size difference between bull and cow within the respective sample. I am also a bit sceptical on that because only the skull and pelvis give clear information on the sex of the individual. And even the skulls can be ambiguous in some cases. For example, the Vig specimen has not very prominent eye sockets and also the horns are less thick, less inwards-curving and more upright than in usual bulls, yet it is tall overall and has tall neural spines in the shoulder area, and therefore likely was a bull. But again, Cis van Vuure’s estimate (see above) sounds plausible and is comparable to what is displayed by Gaurs and Bantengs.

All in all it seems that the aurochs was indeed variable in size. Pleistocene aurochs probably were larger on average than Holocene populations, but not as significantly as it has been proposed by some authors. The average size of the Holocene aurochs probably was around 170 cm height at the withers in bulls and 150 cm in cows, with northern aurochs populations being on the larger end of the bell curve and southern ones (including the subspecies namadicus and africanus) on the smaller end. This accords to the controversial Bergmann’s rule and is found a number of other large mammal species as well. The claim that historic aurochs were only as tall as domestic cattle very likely is an exaggeration, although habitat destruction and hunting perhaps led to another size decrease during the very end of their existence, what are certainly anthropogenic causes.

What does this tell us for breeding-back? Usual “un-improved” Heck cattle (which unfortunately often are promoted as a “rebred” aurochs, what is a blatantly wrong statement) are way too small to fit their ancestor, reaching only 140-145 cm on average. Although domestic cattle were derived from near eastern aurochs, which likely were somewhat smaller than Northern aurochs but still impressive and taller than domestic cattle, there are indeed some modern cattle breeds that exhibit the size of impressive European aurochs. Uncastrated Chianina bulls from Italy can reach up to 180 or more on occasion, and cows about 150 cm. The Maltese ox is a breed that seems to be about the same size. Large Maremmana bulls grow very tall as well, the largest bull I know of reached 182 cm, and the related Podolica and Boskarin are just as big. These tall and slender breeds surely give an impression of what an awesome animal the aurochs was. Some Holstein cattle grow big as well, but this breed is very derived overall.
So, using these very large and more or less primitive breeds, breeding-back can achieve the size of wild aurochs. I think that cattle with a size of 160 cm in bulls in a breeding-back project are satisfying already (and maybe 150 cm for southern Europe), but more size is desirable in any case. 170 cm would be very good and probably authentic; animals even larger than that still can be tolerated or even wanted. In the end, nature will refine the size of a variable cattle population to the amount of space and food that is available.
Most of the Heck cattle breeders do not show great intentions to improve the size of their cattle. But Taurus cattle, which also have a much better overall resemblance to the aurochs than usual Heck cattle, have some bulls ranging between 160-165 already. A further size increase of Taurus cattle (at least in the Lippeaue) is to be expected because of selection and further crossing-in of Chianina and Sayaguesa. Also Tauros Project wants large cattle that appreciate the impressive animal that the aurochs was, using at least Maremmana, Podolica and Boskarin.  


Literature

[1] van Vuure, Cis: Retracing the Aurochs - History, Morphology and Ecology of an extinct wild Ox. 2005.
[2] Claude Guintard: On the size of the ure-ox or aurochs (Bos primigenius Bojanus 1827)
[3] Frisch, Walter: Der Auerochs – das europäische Rind. 2010.
[4] Albano Beja-Pereira et al. The origin of European cattle: Evidence from modern and ancient DNA. 2006
[5] Rene Kysely: Aurochs and potential crossbreeding with domestic cattle in Central Europe in the Eneolithic period: A metric analysis of bones from the archaeological site of Kutna Hora-Denemark (Czech Republic). 2008.

4 comments:

  1. Thanks for the informative article. Do you happen to know an estimate for the total world population of aurochs at the time they were domesticated?

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    1. I have actually no idea, no one has approached that question yet as far as I know.

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  2. I have been wondering lately if there would be any real benefit in breeding back. I was unfortunately imagining a much larger standard size, and your piece on the sizing was quite illuminating.

    I live near Exmoor and would like to see Aurochs roaming wild, but I'm not sure that they would look all that different to the domesticated but free ranging Longhorn cattle. A bit taller, and a bit narrower perhaps. I had been wondering if the inclusion of Simmental genes would increase the size without harm to the mother. My brother bred Simmental into his Hereford herd which was probably a lot more risky for the health of the mothers, due to the dramatic increase in size.

    My reservations would be ecological and whether the Aurochs could be accommodated into modern moorland management.

    Then today, I started thinking about the Irish Elk. The size of a Canadian Moose I believe? Quite another matter.

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    1. Ecologically, the "breeding back" results would work just as any robust cattle in nature management do. If one wants to have cattle that look authentic, then "breeding-back" serves a purpose, if one does not care, it does not. But there are a lot of people that do care, and I am happy about that. Wild Highland cattle or whatever mixes alone would not provide an authentic image.
      I wonder why Texas Longhorn are associated with the aurochs that often. They only bear a remote resemblance to the wild type.

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