Monday, 16 December 2013

The skulls of two Taurus bulls


As promised, here is my post on the two Taurus bull skulls from the Lippeaue that were kindly sent to me by Matthias Scharf from the ABU – many, many thanks!
I tried to evaluate everything useful that I was capable of and took a lot of photos and measurements and compared them with aurochs skulls.

But first, a little introduction to the bulls the skulls are from.
"Luca" (Heck x Chianina) Photo © ABU
The larger one is from a bull named Luca, he was one of the first cross bulls produced by the ABU and was Heck x Chianina. He may have been about 160 cm tall at the shoulders (my calculation based on photos and the actual skull), had a diluted colour due to its Chianina ancestry and was used as a breeding bull in the Hellinghauser Mersch herd until he died 3 years ago. He is the father or grandfather of numerous individuals at Lippeaue, very good individuals like Lamarck among them, who replaced him as breeding bull.

The second skull you might already know from my report of my trip to the Lippeaue, it was one of the skulls I viewed in the field. It’s from a bull called Latino – 50% Sayaguesa, 25% Lidia, 25% Heck. He was selected out because of his comparably small size (I estimate a height of 145 cm for him based on photos) and his nervous and aggressive behaviour (I’m not saying this kind of behaviour is “unnatural” or exaggerated, but I understand that such bulls are extremely difficult to handle). He had a quite aurochs-like overall appearance though, and I suspect that he is the father of this bull I saw at neighbouring Pöppelsche.

And now the skulls:

Luca

Skull length (from frontal bone to nasal bone): 49 cm
Skull length (from frontal bone to premaxilla): 59 cm
Breadth from eye opening to eye opening: 25,3 cm
Breadth between the bases of the horns: 23 cm

Horn cores
Length (outer bow): 63,3 cm
Circumference at base: 31,3 cm
Span from tip to tip: 77 cm

Horn sheath
Length (outer bow): 79,5 cm
Circumference at base: 34,5 cm
Span from tip to tip: 70 cm
Maximum Span: 82 cm

Horn angle relative to the skull: 80°

Latino



Skull length (from frontal bone to nasal bone): 44 cm
Skull length (from frontal bone to premaxilla): 54 cm
Breadth from eye opening to eye opening: 23 cm
Breadth between horn bases: 28 cm

Horn cores
Length (outer bow): 44 cm
Circumference at the base: 28 cm
Span from tip to tip: 80 cm

Horn sheaths
Length (outer bow): 61 cm
Circumference at the base: 30,5 cm
Span from tip to tip: 71 cm
Maximum span: 85 cm

Horn angle relative to the skull: 65°

With 65°, Latino’s horn orientation is within the variation we see in the aurochs. With 80°, Luca’s horns are too upright, altough the Vig bull with unusually upright horns comes close.
It was interesting to see the difference in size and shape between horn sheath and horn core when I detached them. The horn sheath of Luca adds 25,6% to the length of the horn cores, while that of Latino adds 38,6%. It adds 23,3% of thickness in Luca and 27,3% in Latino. Comparing the shape of the horn sheaths with the cores I realized that the sheaths have a much more pronounced curvature. Luca’s sheaths resemble the shape of many aurochs horn cores and curve inwards, but his horn cores are more straight and show almost no curve towards each other. The same is the case with Latino’s horns and probably every bovine in the world. I therefore see two consequences: a) aurochs horns were longer and slimmer at the tips than horn bones indicate and their curvature was more extreme, perhaps similar to this maronesa bull, b) we should consider that if an individual has horns sheaths that look like bony cores of some aurochs specimens, the horns are not identical because its cores would be shorter and less curved.



The superimposings with photos of aurochs skulls were very helpful to see differences and similarities. I did them in lateral (side) view and dorsal view (when the snout is vertical to the ground). I always took the distance between the caudal end of the frontal bone and the eye openings as reference since the length/breadth ratio of the area from the caudal end of the frontal, the imaginary line between the eye openings and the horn bases in both skulls was the same. It showed me that not the entire skull is shorter, but mostly the snout. Also, the eye openings are slightly enlarged in the Taurus bulls, but not much. The skull of the Sassenberg bull is an exception, which was a really long-snouted and small-eyed old specimen. Down below you see the amount of skull length reduction in the two Taurus skulls in respect to the aurochs skulls.


Prejlerup
Berlin
Luca
-4%
-7%
Latino
-12%
-5%


Lund
Vig
Sassenberg
Baikal
Luca
-8%
-7%
-25%
-7%
Latino
-19%
-13%
-34%
-10,3%

According to Nehring 1886 the usual skull length of the investigated aurochs skulls varies between 64 and 72 cm. I wonder whether “skull length” means from the caudal end of the frontal to the cranial end of the nasal or the premaxilla. Let’s assume the former is the case. The arithmetic mean of the relative length difference between the aurochs skulls and the Taurus skulls is about 13%. Increasing the skulls absolute length by the factor 1,13 results in 49,7 and 55 cm. That means that the Taurus skulls are not only shorter but also smaller than usual aurochs skulls, what isn’t surprising considering that the individuals themselves were smaller than aurochs (Latino) or had a proportionally smaller skull (Luca). Also, the nasal bone seems to be shortened relative to the length of the premaxilla in Luca. Interestingly, the nasal bone has two bulges in both skulls instead of one proximal bulge as in the aurochs, what was not visible in the living animals.
Having had a look at the occipital bone, I recognized that the fossae for the attachment of neck muscles forming the so-called neck crest in taurine bulls, wisents, cape and water buffaloes are about as deep and pronounced as in aurochs skulls. This implicates that the crest in the aurochs was of similar size as in bulls of less-derived taurine breeds, what simply makes functional sense.

I also did superimposings with photos of the two bulls in flesh, but they mostly did not work out well because of the perspective. However, one with Luca in profile is quite ok, shown down below. It is interesting to see that the eye sockets protude greatly from the skull in Taurus cattle or Lidia (and probably most other primitive cattle) and the aurochs, but in the living animal the eyes don’t stick out that much, so it probably looked the same in the aurochs.

I also did one with a Maronesa bull in which I shortened the skull of Latino in order to find out how the skull of a short-faced breed would look like compared to the aurochs.


This gif shows Latino’s skull layed over the Maronesa bull’s head, and a version of Latino’s skull with shortened snout to fit the Maronesa’s head, and it lines up very well with the animal. The result was a skull that is 10% smaller than Latino’s head. Now comparing it with the Vig bull, it means that the Maronesa’s head is 21,3% shorter. In the case of the very long-snouted and small-eyed Sassenberg bull (which already had a big difference with Latino’s skull) we get a difference of 59%, what sounds extreme but still plausible. One could argue that this bull is subadult and still growing, but this bull is certainly around 3 years old, and features such as the snout and horn size don’t increase significantly in proportion after that age, although the bull continues to get larger and heavier overall.

With all the information the comparisons between aurochs skulls and my skulls I tried to do a rough reconstruction of an average bull aurochs head. It is based only on what the bones tell me, and focuses on proportional issues and horn shape. I increased the skull/snout length by about 15%, slightly increased the horn size (the relative horn core length of Latino and the Prejlerup skull is identical, but other aurochs skulls have larger horns) and added the parts of the curvature that is missing in his horns (I didn’t put much artistic effort into it, it’s main purpose is to show the proportional differences).

Having evaluated these two Taurus bull skulls and taken note of similarities and dissimilarities, which cattle breeds have heads identical to that of aurochs? We don’t know until a rigorous evaluation of their cranial features is done, using several aurochs skulls for comparison, but based on the characters we can tell from bulls in flesh, some Maremmana, some Lidia (I did a superimposionwith a Lidia steer skull and the Berlin bull here), some Pajuna and some Sayaguesa have bulls with heads looking pretty reminiscent of the aurochs. 

3 comments:

  1. I don't know if this photo of an aurochs skull measurement is of any use to you.I know you seen it before.
    http://www.ahobproject.org/Picture_Library/transition/Full_Size/Ilford%20Bos.jpg

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  2. Sorry for this delayed comment. I find this subject quite fascinating. Please note that my following questions arise out of great curiosity and interest as a complete amateur, not out of any wish to argue. I was struck in this post by the comment that the bull Latino was culled (?) because of his "nervous and aggressive" temperament. A nervous and aggressive bull is surely more of a wild-type temperament than a more docile animal, is it not?
    Is the intention in breeding-back European horses/cattle to create a "park" animal which resembles the ancestral wild species physically but can be handled and is not especially dangerous? I suppose that would be the realistic approach in the European context, I have to admit I'm spoiled as I live in Canada where we fortunately have not exterminated our native megafauna, and we retain immense tracts of wild or near-wild lands. :-) Anyway - If there is any intention to recover a semi-wild temperament, have very many people in the rewilding projects worked with both domestic horses and takhis or zebras, for example? (I haven't done that, but I know both dogs and wolves first hand... there are profound behavioural differences between domestic and never-domesticated species which are best appreciated at first hand :-)

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    Replies
    1. Hi, first of all, thanks for all the comments! Aggressive cattle are selected out for purely pragmatic reasons: They have to handle the animals, and such nervous and aggressive ones are extremely difficult and dangerous to handle. Actually there is a considerable chance that people can be killed when such a bull runs wild - all cattle living under free conditions get more shy, nervous or aggressive, but those with Lidia-ancestry in particular.
      But cattle behaviour is very plastic and environment-dependent. If you release any population of very docile animals into the wild, they will soon return to a wild animal behaviour that probably was very similar to that of the aurochs. Horses not so much, tameness is much more fixated by their genetics.

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