Wednesday, 15 May 2019

The London aurochs skull

My aurochs bull model is finally finished, but before I have the opportunity to take good photos of it, I want to cover an interesting aurochs specimen for today which is one of the individuals that I used as a reference for my model: the London skull

The London skull is a very impressive specimen. It was found in Ilford, London, is from the Neolithic period and on display in the Museum of London. Its sheer size of 91,2cm* from the top of the skull to the tip of the nasal bone as well as its morphology indicates that was a massive, large and fully mature bull. The horns are very thick, especially at the base, and proportionally large. The eye sockets are very prominent and the skull is robust in build overall. It is the largest  and most massive complete aurochs skull that I have seen so far and its length is the largest recorded in the literature (Frisch, 2010). The London bull might have been one of the 190cm tall beasts of the early Holocene. 

* This is very, very large, even for an aurochs bull. The average of aurochs skull lengths is 60-70cm according to the literature, and I found a photo on the web with a scale bar that might indicate the skull is “only” 60 cm long. 

A photo of the skull in profile view that I found on the internet shows that the horns have an angle of  about 70% relative to the snout and the snout has a slightly convex profile. Since the end of the nasal bone is turned down a little bit, I think it might be possible that the snout might be a bit down-turned and round like we see it in some Lidia today (another example how Lidia preserves some of the original aurochs traits and their variation). 

Too bad only the skull of this specimen is known or at least only on display. It must have been a very, very spectacular individual in life. And my model that just has been finished will give you a lively impression for that, stay tuned. 

Thursday, 25 April 2019

Aurochs model: Horns & finish

The shape of my aurochs model made from air-drying clay is finally finished and ready to be painted. I added the curly hair (the mane and forelocks) and the horns. Adding the horns was a crucial and fun step as they are quite an important part of an aurochs' life appearance. 

The reference specimen for the horn shape and size were the Sassenberg, Berlin, London and Baikal specimen. I checked each millimeter, so the dimensions should be correct. At first, I sculpted the bony cores as they are in the original skulls. I started by adding wire of the right size and curvature: 
Then, I started to sculpt the "horn core": 

If you look at fossil skulls, I would say those horns turned out to be very accurate
Before sculpting the "horn sheaths" I painted the horns with red acrylic colour, in order to distinguish them from the new material. The angle of the horn cores to the snout is exactly 65°, which is within the average for northern Eurasian aurochs (Sassenberg: 65°, Lund 60°, Kopenhagen 50°, Vig 85-90°, London 70°, Berlin 70°(?), Baikal 70°; deduced from photos). 
Then, I added the horn tips which would add about 30% to the length (average, but there is great variation) by following the curvature:
After that, I added the thickness of the sheath. As original aurochs horn sheaths are known to have added about 1-2cm in thickness to the bony core, it would be about 2-3mm in the model, which is what I did: 
Then, I completed the shape: 
And sanded it with sandpaper: 

The result resembles the horns of wild yak greatly, which have horns nearly identical to those of aurochs. I think about adding a bit to the thickness of the horns, looking at live yaks and preserved horn sheaths. 

This is what the (nearly) finished model looks like at the moment. I will start painting it as soon as I can: 
The head and horns look a bit huge due to perspective, by the way. 




Sunday, 14 April 2019

Auerrind herd at Groß-Rohrheim

Two days ago, a couple of new recent photos of the Auerrind herd at Groß-Rohrheim, Germany, were published on the Auerrind Project's blog: 
© auerrind.wordpress.com
The white individual in the background is a pure Chianina cow, the two next to it are two Sayaguesa x Chianina (the blogpost doesn't specify the sex, but they might both be female). In the front at the left, there is the Sayaguesa x Grey cattle cow plus the Watussi x Maremmana heifer. 
The Sayaguesa x Chianina individuals seem to have a quite well-shaped anatomy and good size, I am looking forward to see them as adults, and especially F2 of this generation. 
© auerrind.wordpress.com
This is the Watussi x Maremmana heifer. The colour seems to be perfect (phenotypically, it surely is heterozygous for recessive colour dilution genes), the horns are probably going to develop a nice volume. The curvature most likely will be rather straight and upright, but this is to be expected from this combination and can be fixed in later generations. A (Watussi x Maremmana) x (Sayaguesa x Chianina) would be tempting, more efficiently in the form of an F2 x F2 combination. 

It is nice to see that the Auerrind project is still progressing well, especially since the first Chianina xWatussi individual was born recently

Saturday, 6 April 2019

Horn shape evolution in Oostvaardersplassen

I already covered my suspicion that Heck cattle are morphologically changing in the Oostvaardersplassen reserve due to natural selection in a number of posts, see here, here or here. Each of these posts provide photos of individuals endorsing my suspicion. 

And so does this post. A number of individuals in the Oostvaardersplassen reserve show horns that are definitely curving inwards and facing more or less forwards in an aurochs-like manner. Here are photos that I recently discovered via google search: 

- Photo 1 
- Photo 2
- Photo 3 (cow in the front, left)

I am convinced that these three photos all show the same individual and I think it is quite likely that it is the same as on older photos like this one, just fully mature. On photo 2 linked above you also see a cow in the background that also has remotely aurochs-like horns. On photos available in the web, there is also another individual on older photos that shows the same colour morph and horn shape as the cow in the background on photo 2 but more mature, so there are at least 3 individuals born in Oostvaardersplassen that show an aurochs-like horn shape. 

What is striking is that I haven't ever seen any Heck cattle in real or on photos (contemporary or historic) outside of Oostvaardersplassen that show this horn shape, indicating that this phenotype might be unique to the population within the Heck cattle gene pool. While body shape and to a certain degree maybe also proportions can be influenced by phenotypic plasticity, I see now plausible way how phenotypic plasticity may influence horn shape that visibly. Therefore, I think that we see a true shift of allele frequency due to selective pressure, and thus evolution, in the Oostvaardersplassen that is at the same time also a regression towards the wildtype. This is an assumption that endorses a concept of dedomestication as outlined in the dedomestication series

A puzzling question is why we see this tendency only in cows, and not in bulls so far. 

Aurochs model update

About one month passed since my latest aurochs model update, so it is time for another one (please do not use the photos without permission). 

This is what the model looked like about one week ago. The height at the withers is still 33cm. I corrected the nose, added ears, eyelids, tail and penis and scrotum (without the tuft the model looks a bit like an ox to me, by the way). I also made the ribcage broader by about 1cm (not really detectable on the photo). 

As you see on the photos, the back of my model was slightly sloping at this stage - we never see this in wild bovines, only in domestic cattle, which is why I consider that a domestic trait and corrected it afterwards. In the meantime I also sculpted the forelocks, mane and other coat details a European aurochs bull probably had, and now that the body is more or less finished, I start doing the horns. Photos are about to come. 

I have to say it is very exciting and also teaching to do this model. I learned a lot about the three-dimensional anatomy of bovines and I am very enthusiastic about how the model works out. I am incredibly looking forward to doing the horns and painting. 

Monday, 25 March 2019

First Chianina x Watussi is born

Today, the Auerrind project announced that the first Chianina x Watussi calf was born this week. It's a cow calf.

I am very happy to see first individuals of this cross combinations being born. It will be very interesting to see how it will work out in terms of body shape, size, horn size, horn curvature, coat colour - everything will be very tempting to watch in this combination. I am so much looking forward to see this calf growing! 
© auerrind.wordpress.com



Thursday, 21 March 2019

Aurochs model: Work in progress

Here are a few work in progress photos of my new aurochs bull model from air-drying modelling clay that I started in December 2018:

And you see, it is really moving on. The body is almost done, I just started on meaking the ribcage and abdomen a little bit broader as I felt it was too sleek for an adult bull. I use Lidia bulls and extant wild bovines a lot as a comparison. When the body and head is completely done, I will start doing the horns (originally, I planned to make replaceable horns in order to appreciate the variation within aurochs, but that turned out as too complicated so I will sculpt the most common type). After that, the last details that I am going to add will be wrinkles in the skin and hair.
The last step will be to paint it with acrylic colours. I will pay a lot of attention to make a truly convincing colouration.
The model measures 33cm at the withers, and you won't believe that I already incorporated about 10 liters of modelling clay into it.

I am really looking forward to see the model finished and it is great fun watching it progress. I am very, very happy that the model is arithmetically wonderfully anatomically correct, at least I was not able to find any mistakes. Actually, the model so far matches 100% what I imagine a grown aurochs bull to have looked like.

Video of very aurochs-like Lidia bulls

I recently found this video of a couple of Lidia bulls that I find to have a rather impressive morphology on youtube: 
The body shape of these bulls is superb and very wild cattle-like, also the horns of many of the individuals are well-curved and not all too small. If the extremities and horns just would be a little larger and the colour would match, they would resemble wild aurochs to a very large extent.  

I just say how it is: To me, Spanish fighting cattle are the most aurochs-like breed overall that is still extant today. 

Having herds of Lidia individuals like these and supplementing them with portions of Chianina (for leg length and overall size) and Watussi (horn size) would probably lead to stunning results. Then adding a little bit of Sayaguesa and Maronesa, and the strain would be superb from the optic perspective. 

Monday, 4 February 2019

New aurochs model upcoming

In 2015, I did models of an aurochs bull and cow in scale 1:10 made from polymer clay. You can see them on this post, they are displayed at the Alpenzoo Innsbruck now. I think that from an anatomical and artistic perspective, they were good but not perfect. So I started a new model a few weeks ago. 
It measures 33cm at the withers, so it is in 1:5,3 scale to a 175cm bull. I started with a base made from cardboard and wire and added a ribcage made of papier mache. The rest of the model is made/will be made of air-drying modeller clay. 

The basis for the model is my recent aurochs bull reconstruction, which is based on the Sassenberg bull skeleton with added traits from the Kopenhagen skeleton. I am using photos of both specimen as well as that of the Vig skeleton as a guide. So to say, my model is based on three more or less completely preserved bull specimen. 

Here are some work in progress photos: 

I plan to add a special feature to my aurochs bull model: I want it to have replaceable horns that can be seamlessly stuck onto the model, so that I can exchange the horns. I would do one pair of horns for each type of horn shape, size and orientation. The reason is that European aurochs simply had such manifold horns in these three respects (the curvature, however was always the same) so that a model with just one type of horns would not appreciate this nearly enough. I will do a test if this is practically feasible and present the various horn types that I am planning to do in a future post. 

I am looking forward to finishing the model and hope it works out that well. I am continuously checking the model for accuracy (proportions, shape) by doing measurements and using photos and comparing it to the original skeleton(s). When it is done, I am going to paint it with acrylic colours. 

If course I am going to paint it in the best-supported (or, to  put it differently, the only supported) colour scheme for European aurochs bulls: completely black with a light dorsal stripe and a (perhaps reduced) muzzle ring. But there are other colour variants that are also plausible for an aurochs bull (go here). In order to appreciate that, I am also planning to do multiple models (perhaps only about 8-10cm withers height), all copies of each other, and paint them in the other colour variants that might be plausible.  

Maybe I am also going to do female for the bull, in the same scale and also based on my most recent reconstruction. I would also do some mini models for the cow in order to appreciate the many colour variants plausible for aurochs cows as well. A model for an Indian aurochs would also be very tempting. 

I know these plans are ambitioned but I hope to finish the large bull model at least and I am very optimistic about that one. 

When the basic shape for the aurochs bull is done, I will use it for a volumentric weight calculation in order to get an idea for the weight of a grown aurochs bull. 


Sunday, 20 January 2019

The last aurochs hybridized with cattle in the wild

Domestic animals and their wild counterparts are usually able to interbreed freely and produce fertile hybrids. Thus, it is always likely that everywhere they share their habitat, they might interbreed and thus mutually influence their populations. Domestic animals always might escape, and wildtype animals always might leave a track in domestic stock by occasional mating. 
When discussing whether aurochs and cattle interbred in Europe, it mostly concerned the question if local aurochs left a genetic trace in cattle populations. The other way round, domestic cattle influencing local aurochs, was not examined yet. However, I have always considered it very likely that escaped domestic cattle left a trace in European aurochs. It happens everywhere where wildtype and domestic type are neighbouring – you see that in wolves (some colour variants, such as black in wolves, are believed to have been inherited from domestic dogs), in wild boar displaying domestic colour, and it has also been proven for late European wild horses that inherited the emutation from domestic stock (see Pruvost et al. 2011). I see no reason why it should not have happened that escaped domestic cattle interbred with aurochs and left a detectable trace in wild populations. 

This interesting question has now been examined by Bro-Jorgensen 2018. A number of ornamented drinking horns from medieval times or shortly after that are suspected to stem from aurochs because of their shape and size have been genetically analysed for mitochondrial haplotypes and sex. The sample also includes the horn of the last aurochs bull that died in Jaktorow, Poland, in 1620. 
Medieval aurochs drinking horn - large, thick and evenly curved
Horn of the last aurochs bull - smaller, thin and not that curved
All of the horns tested turned out to be from males – considering their shape I would be surprised if turned out otherwise – and most of them have the aurochs haplotypes P. The horn of the last bull and two other drinking horns, however, surprisingly carry the haplotype T, which is widespread among taurine cattle. While the origin of the two drinking horns might not be that clear, it is very likely that the claimed horn of the last aurochs bull is indeed from this population and individual. It is also very likely that the population in Jaktorow was not simply a feral cattle population because of historic reports. Thus, the most likely conclusion is that aurochs of the latest centuries, or at least the remnant population at Jaktorow, was genetically influenced by escaped domestic cattle. As this influence is found on mtDNA, which is maternally inherited, the influence must be from a domestic cow at least. Influence from domestic bulls is of course also possible, but was not examined and domestic bulls probably had a hard time competing with wild aurochs bulls anyway. 
Natural selection would probably eradicate most of the domestic influence, except for factors with little selective pressure on them, such as these mitochondrial haplotypes. Perhaps, if the domestic influence was widespread towards the end of the existence of the aurochs (when space became increasingly limited and thus they often neighboured domestic stocks) there also were aurochs populations displaying domestic colour variants, although no such cases have been reported in historic texts. Domestic cattle influence also shows in American bison, where it is particularly visible in horn shape and size (see here, for example). The horn sheath of the last aurochs bull was comparably small (only 45 in length, which is considerably smaller than the bony cores of earlier aurochs males). Even if it was a young individual at the time of death, most likely the last aurochs population had comparably meagre horns as a consequence of limited resources and trophy hunting, but domestic cattle intermixing might be a further reason. This would also explain why the curvature is not nearly as intense and even as in the older drinking horns (cattle intermixing affects horn shape in wild bovines as the bison example shows). 

This discovery is interesting and totally what I expected and predicted. Questions that are particularly intriguing are how widespread and intense that domestic introgression into local aurochs population was, and how large the influence on the visible phenotype of these aurochs population was. 

Literature 

Pruvost et al.: Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art. 2011. 

Monday, 14 January 2019

Albatros, the Heck bull, vs. aurochs

When looking through Walter Frisch’s Der Auerochs (2010) I found a photo of the Heck bull Albatros in perfect profile view (the photo is © Walter Frisch, I hope it is ok for Mr. Frisch that I use it here). Let us have some fun with it! 

A profile view photo is pretty useful for a direct comparison with the aurochs. When using a single Heck individual, it is always important to pick one that is a fair representative of the breed. For example, it would not be fair to pick one of the hyper-massive dachshund bulls that are still found in the breed that are not nearly of the same quality as the mean, or to choose an individual that is considerably better than the average. I think that Albatros is a pretty fair choice. It is from the Wörth/Steinberg line bred by Walter Frisch, which is remarkable for having large and well-shaped horns (some of them are excellent, take a look at them here). The Wörth lineage is, speaking of body morphology and size, very typical for Heck cattle on the other hand, so Albatros is very representative of the breed. 

I took my most recent reconstruction of an aurochs bull as a comparison. I introduced this reconstruction in this post and I consider it pretty accurate. So I copied the reconstruction and the photo of Albatros next to each other to same scale. For Albatros, I used a withers height of 140cm, which is pretty average for Heck cattle (bulls of the Wörth lineage are sometimes claimed to reach 160cm, but I do not consider this plausible for Heck cattle, especially since I saw the herd myself), and for the aurochs I used 170cm withers height – 170cm is the mean withers height found within this species. There are populations where bulls reached only about 150cm but also giants with a withers height of about 190cm or more (see How big was the aurochs really?), so choosing 170cm seems fair to me. 
Here you see the comparison of both animals in flesh and below that a comparison of both skeletons (the photo of the Heck bull is suitable to deduce the skeleton of the living animal, it is not as precise as an X-ray but an approximation based on anatomical knowledge – I already did this with several cattle individuals on Comparing skeletons with skeletons). I go over the differences both in morphology and behaviour. 
Skeleton of the Heck bull, deduced from the photo
Skeleton of the Kopenhagen bull
Morphological differences: 
Size.In absolute height, the Heck bull is of course smaller than the aurochs by about 30cm. However, in mass, both animals might be equal. Massive Heck bulls reach a weight of about 900kg [1], which is probably also the upper weight range for aurochs bulls (more on that in an upcoming post). So technically speaking, both animals have the same mass, but distributed differently – an aurochs was built way higher and shorter than most domestic bulls. 
Proportions and skeleton.This is where we have considerable differences. First of all, the trunk of the Heck bull is elongated while the size/length of the limbs shrunk – the ratio of the distance from the hooves to the shoulder blade (note: not withers height) and to the end of the pelvis is exactly 1:1 in the aurochs, and 1:1,13 in the Heck bull. The head size also shrunk dramatically, as much as – most likely – also relative brain volume. The skull shape is clearly paedomorphic – it is shortened, especially the snout, and the eyes are enlarged. Those changes in the skeleton and proportions are typical consequences of domestication that we see in nearly all domestic mammal species that have been domesticated. Also, the length of the processus spinosi in the shoulder area (“hump”) is greatly reduced in the domestic bull – while the spines go well beyond the shoulder blade in the aurochs, they are actually shorter than the shoulder blade in the Heck bull. This is also typical of domestic cattle while humps are universal for wild bovini. The comparison of the two skeletons shows the dramatic differences in the skeletal build of an aurochs bull and a domestic bull. 
Soft-tissue anatomy. The muscling of the Heck bull is reduced compared to a wild bovine, which is especially obvious in the pelvic area. Also, the size of the intestinum increased dramatically, causing a huge belly compared to the wildtype. All in all, the soft tissue morphology of this Heck bull is clearly domestic and as such very reminiscent of what we see in dogs with a certain hormonal disorder (cushing syndrome, see this post). The skin is more flappy, especially the enlarged dewlap, and also the scrotum is elongated. 
Horns.The horn volume (length and thickness) is well within the range of an aurochs. The orientation of the horns relative to the snout as well – in Albatros, the horns curve away from the skull in an 75° angle. The literature gives an average horn curvature of 50-70°, but in reality the spectrum is larger (the largest angle I have seen so far is about 90° in the Vig bull and the narrowest 40° in the oldest aurochs skull). The only difference between Albatros’ horns and that of an aurochs is that the curvature (the “primigenius spiral”) is not intense enough. The horns should curve more inwards. A less intense curvature or a tendency of the horns curving more outwards is also a classic domestication trait for bovines. 
Colour. The colour setting and thus the responsible alleles seem identical to that of the aurochs, with two exceptions – the sexual dimorphism (not only in colour) is considerably reduced, which shows in the light brown shade on the dorsal area of the Heck bull, and it is from a population that also has alleles for domestic colour variants such as white spots or colour dilutions. 

Behavioural differences: 
We have no living aurochs to compare the behaviour with, so we take the typical behaviour of a wild bovine as a reference. 
The fight/flight reaction in this bull is greatly reduced. It is, compared to a wild bovine, very agreeable, docile, tame, trainable and its activity level is lethargic compared to the wildtype. 

Comparing the Heck bull trait by trait with an aurochs, it shows that this animal is actually as domestic as can be, and the similarities to the aurochs are limited to colour and horns*. But that is not to say that the bull Albatros or the breed Heck cattle is a failure from the “breeding-back” perspective, not at all. One could analyse any domestic cattle breed the same way and would get similar results. Domestic cattle are simply comparably removed from their ancestor after 8.000 years of domestication. For details, see the article What breeding back can achieve

* I am aware of the fact that this Heck bull is probably able to sustain itself in the wild, which is also true of all landraces and also many derived breeds, and it would also show the same social behaviour repertoire as the aurochs (most likely), which is also true of all living cattle. 

Literature

Bunzel-Drüke, Finck, Kämmer, Luick, Reisinger, Riecken, Riedl, Scharf & Zimball: Wilde Weiden: Praxisleitfaden für Ganzjahresbeweidung in Naturschutz und Landschaftsentwicklung


Friday, 11 January 2019

From aurochs to cattle: step by step

In the post The real differences between aurochs and cattle I go over the organismic differences between the aurochs and cattle in regards to morphology, development, endocrinology, behaviour and genome. Those differences all are interconnected and were caused by the process of domestication. You cannot alter one factor without altering several others at the same time. Each of those factors, like changes in hormonal activity or development, have a particular impact on the organism. With this post, I want to illustrate these impacts by turning a wild aurochs into domestic cattle step by step. I do not say that these changes evolved in this particular order, rather they evolved more or less at the same time but varying extent, this is just a scheme. Please do not use my drawings without permission.

This is the starting point, a wild aurochs: 

Hormonal changes 

Changes in thyroid hormones not only caused a more relaxed, lethargic behaviour but also reduced limb and head size, making the overall appearance of the animal more elongated. Probably horn size would be affected as well. Also, the animals do not grow to full size anymore. 

Another consequence of hormonal changes, of corticosteroids in particular, would be reduced muscling, a hanging spine and an enlarged intestinum. It becomes apparent that this is the factor that causes the animal to truly look domestic – the deformed skeleton and reduced muscling simply does not look compatible to a wild animal. The drawing above reminds me of a Sayaguesa bull, by the way. 

Developmental delay 

The delay in development causes a phenomenon called paedomorphy, resulting in a calf-like skull morphology, shortened horns and reduced sexual dimorphism. Also the shrinkage of the hump might be caused by developmental delay. A lot of cattle landraces, like Rhodopian short horn for example, look like this drawing. 

Pleiotropic effects 

Genes affecting behaviour also affect other factors, such as coat colour. As a result, the animals will start to show spotted colour because the activity of pigment cells is distorted. Furthermore, horn shape is affected as well, they start to curve more upwards and outwards as in all domestic bovines. 

New mutations 

New mutations for new phenotypic traits evolve. Such as for changes in horn shape or curvature, horn size (smaller or larger), stubby legs, shortened snouts, overlong hair, curly hair all over the body, and a whole palette of new colour mutations. The skin also gets more flappier with enlarged or elongated appendages. Cows evolve a dramatically enlarged udder as a result of direct selection on this trait. 

Adding all these factors, we get the domestic cattle that we have today. 
 And here is an animated GIF for this transformation: 


For deeper background information, see these posts: 

Sunday, 30 December 2018

What to do with the wisent in the Caucasus?

The Caucasus mountains were home to another subspecies of wisent, Bison bonasus caucasicus, until was exterminated in the first half of the 20thcentury (it is also considered a separate species by some authors). Nowadays, wisents have been reintroduced in the western Caucasus reserve, and this population is controversial for its special history. In this post I am going to explain why, have a look at the arguments against this population, why I consider it beneficial instead and what to do with it for the future. 

First and most importantly it is to note that the modern wisent went through a severe genetic bottleneck event. All modern wisents descend from only 12 founder individuals and thus the genetic basis of the species today is extremely narrow. The consequences of this a considerable inbreeding depression affecting skeletal growth leading to skull asymmetry, deformation of the male gonads, increased rate of stillbirths, decreased female fertility and reduced resistance against diseases and parasites. They are particularly vulnerable to posthitis, balanoposthitis, foot-and-mouth disease, cattle tuberculosis, bluetongue disease and others. 20% of the mortalities in the Bialowieza Forest are caused by diseases. The inbreeding depression is an immediate danger for the long-term survival of the species and an obstacle for the establishment of populations in the wild [1]. It is not rare that reintroduction attempts fail due to these effects or that whole stocks in zoos diminish because of diseases. Therefore, the species is still in danger of extinction [1]. 

That is why during the population crash in the 1920s and 1930s wisents were crossbred with American bison systematically in order to prevent an inbreeding depression. When an international herd book for pure wisent was set up, most of the hybrids were exterminated (and the expected inbreeding depression came). However, a herd of hybrids was released in the Caucasus in 1940. Subsequently the wisent percentage in the herd was increased by culling of hybrid bulls and release of pure wisents (absorptive breeding), so that the bison percentage in the modern herd is estimated to be as low as 5%. However, the hybrid influence is definitely recognizable (see here, here or here for individuals with a clear bison influence; it is not that much visible in these for example)* 

* It is interesting that the genealogic percentage is estimated that low while their phenotype is looks exactly intermediate between both species. One explanation might be that individuals with a high portion of bison genes might simply have a higher evolutionary fitness and thus the phenotypic influence of bison is still present despite absorptive breeding. 

Some authors suggest a culling of the population. There are a few arguments on why those hybrids are supposed to be maladapted and have been a bad choice for the Caucasus ecosystem: 
- allegedly the hybrids lack mountainous adaptions due to the influence of the plains bison
- allegedly, the plains bison influence made them less resistant to cold 
- allegedly, the plains bison influence has a destructive influence on the local flora 
First of all, Lowland wisent (B. b. bonasus, the only remnants of this population) do not show the mountainous adaptions of the Caucasus wisent either (which was smaller, had shorter and more rounded hooves), so the bison influence is probably not to blame on that. Furthermore, the claim that they are less cold tolerant due to bison influence is most likely incorrect as American bison resist temperatures down to -40° Celsius. Whether or not they have a destructive influence on the flora is probably subjective. The only dietary difference between American and European bison is that the American species consumes more grass than the European one. However, in the ecosystem there once were two other grazer species, aurochs and horses, so that the impact from the hybrid bison cannot be destructive for this ecosystem as it still lies within the spectrum covered by wisent, aurochs and horse. As we know, large herbivores do have an impact on the vegetation – they tend to open the habitat and stop or reduce forest growth. This is considered beneficial for European landscapes and biodiversity (intermediate disturbance hypothesis) which is why large herbivores, wisents among them, are (re)introduced in many nature reserves. Ironically, the same kind of influence that is considered beneficial elsewhere is considered a damage in the Caucasus reserve, serving as an argument to cull the population. Pure wisent would probably do exactly the same. 
Actually, I see no objective ecologic justification for culling this population and no alleged maladaptation as a result of hybridization. The sole remaining reason why this population is considered a threat is their hybrid ancestry. 

Back in the 1920s and 1930s, when there was no international herd book, hybridization was indeed a threat for the genetic integrity of the whole species. The Barbary lion, for example, is a subspecies which died out on genetic level as there are probably no remaining pure individuals due to hybridization. However, nowadays the situation is different. The pedigree of each wisent considered pure is documented in the pedigree book, and wisents that are not listed in the pedigree book are ignored to death anyway (this concerns about 700 wisents in Europe). Therefore, the existence of a wild hybrid population in the Caucasus is not a danger to captive pure herds (however, there is a neighbouring pure herd in the region, but I come back to that later). It is probably the mere existence of the hybrids that irritates some authors so that they suggest the culling of the whole population. 

Nevertheless, I want to look into the positive aspects of this population.  The inbreeding depression we see in the wisent is the result of the high degree of homozygosity in the population which leads to an expression of the effects of deleterious alleles. This can only be overcome by the introduction of new alleles in order to reduce the frequency of the deleterious alleles. Hybridization introduces new alleles and the closest living relative of the species is the American bison, so this species would offer as a possibility to increase genetic diversity. 

Hybridization of course introduces alleles specific (=diagnostic) for the foreign species, but could also introduce alleles on loci that are not relevant for the differences between wisent and bison as such but where wisent are homozygous for deleterious alleles. Thus, hybridization, when the right alleles are introduced, can help to overcome the inbreeding depression of the wisent affecting development, fertility and resistance against diseases without affecting its genetic integrity and thus be beneficial for its chances of survival as a species. Of course rampant hybridization without any kind of selection just produces a phenotypic and genotypic mosaic or mess, which is why some sort of directive selection would result in the desired goal: increasing the genetic fitness of the wisent without grossly affecting its genetic integrity as a species. Therefore just keeping those hybrids in zoos without any selective breeding would lead to technically nothing. However, in the population in the Caucasus, we have something special or even ideal acting upon their gene pool: natural selection. The start-up population was a bunch of hybrids from zoos, but since 1940 they experienced more than 70 years of natural selection. It is likely that the frequency of deleterious wisent alleles on the respective loci has decreased as a result of the higher fitness of newly introduced alleles from American bison, therefore decreasing the effects of the inbreeding depression. To put it simply, those hybrids with a healthier genetic make-up have a selective advantage over those with a high degree of deleterious alleles. I therefore expect the hybrid wisents in the Caucasus to be healthier, more resistant against diseases and have less problems with fertility and development than pure but highly inbred wisents. I strongly opt for studying the health and fitness of this population. As far as I know, this has not been studied before as there is little scientific interest in hybrids, especially for those in the wild. If the hybrid population in the Caucasus is indeed healthier and more evolutionary fit than inbred pure wisents, conservationist have one way to interpret it that can be expressed in two ways:
- Non-hybrid wisents are pure but dangerously inbred. Hybrid-influenced wisents are not pure but healthy and evolutionary fit. 
- Non-hybrid wisents are dangerously inbred but pure. Hybrid-influenced wisents are healthy and fit but not pure. 

In any case, the hybrid population in the Caucasus is probably the largest (in their best times up to 2300 animals) and healthiest wisent population since the population crash in the 1920s due to hybridization and several decades of natural selection. I am definitely not suggesting to crossbreed wisent and bison rampantly and simply release them in the wild. One argument against the hybrid wisents would be the phenotypic mosaic they are displaying which is probably the result of lacking selection on diagnostic wisent traits. The goal should be a population of wisents with increased fitness (i.e. reduced frequency of deleterious alleles) due to hybridization without any recognizable phenotypic influence from American bison in ecology, morphology or behaviour*. 

* Bison and wisent have different modes of combat behaviour. Bison butt their heads against each other while wisents fight more in a cattle-like manner by pushing and pulling with their horns. I know of now records on how the Caucasus population behaves in this respect. 

This could be achieved in a large-scale breeding project, but for the Caucasus population the solution is to increase the wisent portion in the gene pool while retaining their wild state, so that the fitness-increasing alleles donated by bison keep on replacing the deleterious alleles. One way would be to continue the absorptive breeding by culling wild hybrid bulls and releasing pure wisent bulls in the population. The problem is that this way is comparably un-directed. It would increase the wisent alleles in the gene pool, but the diagnostic wisent alleles as much as the deleterious alleles that are to be purged out. Therefore another possibility would be to release a sufficient number of pure wisents that merge into the hybrid population, so that the wisent genes find their way into the population by natural selection alone without human help. This way the survival chance for beneficial alleles is higher while the wisent percentage is still increased. This could be done several times in subsequent decades, until no American bison influence is visible in the population. 

As I wrote above, there is a neighbouring population of pure wisents in the Caucasus. The authors of the action plan for the conservation of the wisent 2002 fear an intermix between the pure and the hybrid population because they consider the hybrids, as written above, worthless and ecologically maladapted (for which, as I explained, there is no basis). I, however, hopethat there will be an intermix. It would be beneficial for both populations: beneficial alleles might enter the pure population while the wisent percentage in the hybrid population will increase. 

Although hybridization has been proven to be part of evolution in nearly all groups of related vertebrate species where it has been exanimated (see here), it is still deemed the absolute doom in conservation. This is, at one hand, probably a relict of the 19thcentury picture of nature as a stable household system as much as the lesson from cases where uncontrolled hybridization indeed threatened or threaten the genetic integrity of endangered species. However, in the wisent it is the extremely narrow genetic base that threatens the long-term survival of the species. A rigorous study of the fitness and health of the Caucasus population could indeed provide a good argument for cautiously increasing the genetic diversity in the wisent via bison introgression in single controlled populations. Due to the pedigree book, the influence would be transparent anyway (a separate herd book for these new lines could be set up). 

In the eyes of others, it is more sensible to shoot them all and replace them with a population pure wisents that have the same fitness problems as anywhere else and might crash at any time.  
If anyone was to ask me personally which kind of animal I would prefer, a wisent that is 1/8 or 1/16 bison on both its parental sides and therefore healthier and more evolutionary fit or a pure wisent that is highly inbred with all the according problems, I would, honestly, go for the first option. 

I already covered the wisent population in the Caucasus in these two posts: 

Literature

[1] Mammal Research Institute, Polish Academy of Science: European Bison Bison bonasus: Current state of the species and an action plan for its conservation. 2002


Sunday, 23 December 2018

The Origin of Maronesa

Back in a 2013 post, I called Maronesa a “relict breed” from Portugal. Not because of an alleged isolated ancient origin, but for its flawlessly aurochs-like colour make-up, the well-expressed sexual dimorphism and the inwards-facing horn curvature. 
Now there is a kind of quarrel on the English Wikipedia page regarding the origin of this draft breed. While enthusiasts of the breed claim a separate origin that is strongly influenced by local aurochs, others are convinced that it has its origins among other local breeds and is closely related or descends from Barrosa and Mirandesa. So here is my take-on to this subject based on literature references, old photos and the phenotype of Portuguese cattle breeds. 

First off, Maronesa has traditionally been considered a crossbreed of Mirandesa and Barrosa because of historic evidence [3]. It has been considered a mix population until it was categorized as a separate breed in 1835[1]. A genetic study from 1998 found a genetic distance to other Portuguese breeds [2]. However, another study from 1993 found it to be genetically intermediate between Barrosa and Mirandesa [4], which is in line with the historic evidence. Another study from 2004 found Maronesa to group closely with Barrosa [5]. 
The claim, however, that Maronesa has an isolated origin (even from from local aurochs) is not based on any genetic or archaeological evidence. Advocates of this scenario base it solely on the ground of physical traits plus the one study from 1998 that places Maronesa apart from other Portuguese breeds. The physical traits of Maronesa are not a good argument for an isolated origin. At one point, all domestic cattle had a very aurochs-like appearance since all of them descend from the aurochs. In cladistics you would say: you cannot base relationships on plesiomorphies. Furthermore, the aurochs-like morphology of Maronesa mainly concerns the coat colour scheme, the well-marked sexual dimorphism and the horn shape. While the dimorphism is indeed exceptionally good, you also find these traits in other breeds. 

Looking at the external appearance, it also becomes apparent that Maronesa has striking similarities to Barrosa (and the closely related Cachena), Mirandesa and also Arouquesa – all of them are neighbouring breeds from the same region. The similarities concern body shape, horn shape and face shape. Actually, many Arouquesa in fact look like a lighter-coloured and slightly more bulldoggish version of Maronesa. Thus, the striking phenotypic similarities plus the geographic and genetic proximity of these breeds suggest a common origin for these breeds to me. Phenotypic similarities can be misleading in domestic animals, but those of these five cattle breeds look very diagnostic and when you look at retriever dog breeds, the Irish setter and spaniels, you would also suggest a common origin or mutual influence between those breeds based on their looks – and this is exactly what is documented in their breeding history. 
Maronesa is slightly more aurochs-like than the others because of its colour – the colour is way darker than in the other breeds, making primitive colour traits like the eel stripe or sexual dichromatism more visible in Maronesa than in others. But this can be caused by only one or two alleles alone, so the difference is not that considerable. 
However, the darker colour would be an argument against a hybrid origin of Mirandesa and Barrosa for Maronesa: it is coloured darker than both of its alleged parent breeds. Also, the morphology of both Barrosa and Mirandesa is way more over-bred than in Maronesa. Thus, Maronesa seems to be more primitive and therefore cannot descend from two more derived breeds. But you have consider the origin date for Maronesa: it has been considered a separate breed since 1835, thus the origins of this breed must date back at least to the first half of the 19thcentury. All of the breeds were less-derived than today. There is a photo of old Barrosa in black and white where you can clearly see that Barrosa was way less derived than today (the individual in the front seems to be a steer). This goes for the colour (the steer seems to have a rather dark colour) as much as for body shape and skull shape. This, on the other hand, makes it credible again that Maronesa is indeed a crossbreed of Barrosa and Mirandesa. 

And even if it does not directly descend from a mix of those two breeds, I think it is very likely that the breeds Maronesa, Barrosa/Cachena, Mirandesa and Arouquesa share a common origin from the same region of Portugal somewhere in around 1800. The phenotypic similarities and the geographic proximity are striking and there is also genetic evidence backing it up. 
Thus, the scenario of Maronesa being an isolated relict breed that is somehow more closely tied to the aurochs than other Portuguese breeds is romantic and tempting looking at its colour and horns, but evidence suggests otherwise. And personally, I consider the similarities between aurochs and Lidia more deep-going than in Maronesa (see here or here). 


Literature 

[1] Marleen Felius: Cattle breeds: An Encyclopedia. 2005. 
[2] Fernandez, Iglesias & Sanchez: Genetic variability and phylogenetic relationships between ten cattle breeds from Galicia and the north of Portugal. 1998
[3] Porter, Alderson, Hall, Sponenberg: Mason’s world encyclopedia of livestock breeds and breeding. 2016. 
[4] Iannuzzi & Figueiredo: Frequency and distribution of rob (1;29) in three Portuguese cattle breeds. 1993 
[5] Mateus et al.: Genetic diversity and differentiation in Portuguese cattle breeds using microsatellites. 2004