The coat colour variation in the Przewalski's horse #2

In the previous post, I wrote that wild-caught Przewalski’s horses from the 19^th and early 20^th century displayed more colours than the modern population does after the genetic bottleneck in the middle of the 20^th century. These colours included the lack of pangare, lightly coloured legs, possibly non-dun (at least a rather dark colour instead of the light sandy colour that many individuals show), and very lightly coloured individuals. 

In the comments, two photos were linked that, however, undoubtedly show modern Przewalski’s horses lacking pangare. They are from the population at the Hustai National Park in Mongolia and can be seen here (photo #1) and here (photo #2). 

This shows that the non-pangare allele is definitely still present in the population, albeit its frequency seems to be greatly reduced. What is also interesting is how dark the colour of the non-pangare individual on photo #2 is. It is not quite as dark as the stallion Schalun from the early 20^th century which I mentioned in the previous post, but it is certainly darker than a Gotland pony, which has been found to carry both the non-dun1 and the domestic non-dun2 allele, but not the dun allele. I think it is not unlikely that this individual has the non-dun1 allele – when you compare it with the stallion on photo #1, which is definitely bay dun, you can see a clear difference to the individual on photo #2. Looking at the other individuals on photo #2, it seems that they have the same base colour on the neck and face, and the rest is diluted by pangare, which is very prominent on these individuals. So they might have the non-dun1 allele too. If that is really the case, the non-dun1 allele might be present in more modern individuals than only those in this herd, just not as apparent because the colour is diluted by pangare and non-pangare individuals are pretty rare in the modern population. But without a genetic test on the Dun locus in these individuals this is a speculation. 

This sparked my interest in the Hustai herd and I searched for images on google. As it happens, I even found an individual with lightly coloured legs (go here). I also found a rather pale individual from Hustai NP, but it was in its winter coat and the winter coat is always lighter in colour. 

 

This shows two things: some of the colour variants considered extinct by the sources I cited in the previous post are still present in the modern Przewalski’s horse population, and the Hustai herd seems to be rather variable in colour. I am curious on the background of this herd – since the Przewalski’s horse was killed off from the wild in the 20^th century, this herd must descend from individuals in captivity, and I wonder which location(s) the animals are from as they preserve all these colour variants that have become incredibly rare in the modern population. 

The original coat colour variation in the Przewalski's horse

The modern Przewalski’s horse has a comparably uniform coat colour: a bay dun base colour often with a reddish tone, combined with the prominent countershading and white muzzle (pangare). This has become the standard colour scheme for wild horses. There is some variation, some individuals are more reddish than others, some are more lightly beige in colour, but apart from that, current Przewalski’s horses do not vary greatly in colour. 

However, what we see in modern Przewalski’s horses is the result of the genetic bottleneck due to the population crash in the 20^th century. Photos and descriptions of individuals prior to the genetic bottleneck event from the late 19^th century and early 20^th century show that originally there was much more variation in the coat colour of the Przewalski’s horse than what is the case now, also including colour alleles that have disappeared from the modern population. 

There were both very dark and also very lightly coloured individuals in the herds. They were not geographically separated but from the same populations and were often sold together [1]. An example for such a lightly coloured individual was a stallion caught from the wild and brought to the Haustiergarten Halle, Germany, in 1901 [1]. Some modern Przewalski’s can be more lightly coloured than others even today, but the photos show that some individuals prior to the bottleneck were very light in colour. A famous example for a dark individual is the stallion Waska, which was the first Przewalski’s horse brought to Europe and could be ridden [1] (you find a photo of him on Wikipedia). The photos of this and other dark individuals show that the countershading is slightly reduced, and that the colour is way darker and less shaded than in the modern Przewalski’s horses. I think it is well possible that these dark individuals had the non-dun1 phenotype caused by the d1 allele being present homozygotely on the Dun locus. This allele has been found in a 42.000 years old wild horse and a roughly 4.000 years old horse, both from Siberia [2]. The youngest date for the separation of the Przewalski’s horse’s lineage and that of the domestic horse was 38.000 years ago [3], making it possible that the non-dun1 allele was present in the wild populations before the lineages separated. Another stallion from the early 20^th century that was documented in photographs, named Schalun [1], was so dark that I think it is very unlikely that it had the dun dilution. It does not look as if it was the domestic non-dun2 mutation, the colour resembles much that of some Gotland ponies, which were found to have the d1 allele [2]. It is of course possible that Przewalski’s got the d1 allele via introgression from domestic horses but considering that the allele was already present in late Pleistocene wild horses, it is more parsimonious that the dark-coloured Przewalski’s horses were a reflection of the original wildtype diversity in the wild horse, if those individuals indeed had the d1 allele. 

Pangare (light ventral countershading with a white muzzle) is typical for wild equines, and all modern Przewalski’s horses have it. However, it was not uncommon that wild-caught Przewalski’s horses completely lacked pangare, f.e. many of the wild horses brought to Askania Nova in the early 20^th century [1]. These horses lacking pangare must have had the non-pangare allele Pa^np. It is certainly possible that this was the result of domestic horse introgression in the wild that undoubtedly took place, but I think it is also plausible that this allele first appeared in wild populations, as some cave paintings show horses that definitely lack pangare. Cave paintings, however, must be taken with caution. Only a genetic test of predomestic wild horse DNA samples could clarify if non-pangare was a wildtype or a domestic allele. 

There were also individuals with lightly coloured legs. Usually, in wildtype-coloured horses (be it bay, bay dun, black, black dun) the distal half of the legs is coloured dark to very dark, except for a light area at the back of the leg of varying extent. Apparently in some individuals this light area extended across the entire leg, resulting lightly coloured legs. There is at least one photograph of an individual having such legs [1], and descriptions of wild Przewalski’s from the late 19^th century mention lightly coloured legs. 

 

I did an illustration of the original coat colour diversity found in the Przewalski’s horse. It shows, from top to bottom and left to right, the colour type that is now prevailing in the population, the dark variant that is possibly non-dun1, the non-pangare one (I combined it with the dark variant, based on the stallion Schalun, but of course also lighter coloured ones could be non-pangare), the lightly coloured legs, and the very lightly coloured variant. All these illustrations are based on photographs of actual individuals that lived in the early 20^th century and often were caught from the wild. 

 

What happened to the colour variants not present in the modern gene pool anymore? One reason for their disappearance was the population crash in the 20^th century, which caused a reduction in allelic diversity. Another reason is, in fact, selective breeding. It was very likely the case that the lighter-coloured individuals with pangare and visible leg stripes were preferred in breeding because the responsible breeders thought that a wild horse must look that way [1,4]. This idealization of the Przewalski’s horse appearance caused these colour variants to disappear – there are no non-pangare individuals anymore (EDIT: There are in fact some non-pangare individuals surviving in Mongolian herds at least), and also no very dark, possibly non-dun, but also no very lightly coloured ones [1,4]. I do not think these variants were actively selected against, but apparently nobody paid attention on preserving them in the gene pool, resulting in their disappearance. 

 

The current Przewalski’s horse is not completely free of domestic horse introgression. As a consequence, domestic colour variants occur from time to time. Some herds may have individuals with a white stripe on the face [1], others show a chestnut colour [1,4], what means that the e mutation on the Extension locus has been introduced into the Przewalski’s horse gene pool by interbreeding with domestic horses. 

 

Therefore, while some wildtype colour variants have been lost in the last remaining wild horse, domestic ones have been introduced. This is of course not desirable for maintaining the original wildtype diversity. This could, theoretically, be fixed. For example, herds in which chestnut Przewalski’s have appeared could be tested for the eallele, and those selected out, what, on the other hand, bears the danger of selecting out wildtype diversity that is needed in the limited gene pool. The non-pangare allele could be reintroduced either by gene editing (which would be effortful) or crossing in a non-pangare domestic horse (which would be controversial for good reasons). But it is questionable if single colour alleles are really that important. 

EDIT: modern representatives of these colour variants can be seen here. 

 

Literature 

 

[1] Volf, Jiri: Das Urwildpferd. 1996. Neue Brehm-Bücherei. 

[2] Imsland et al.: Regulatory mutations in TBX3disrupt asymmetric hair pigmentation that underlies Dun camouflage colour in horses. 2015.

[3] Orlando et al.: Recalibrating Equus evolution using the genome sequence of an early Middle Pleistocene horse. 2013.

[4] Oelke, Hardy: Wildpferde gestern und heute – Wild horses then and now. 2012. 

Genetic research not done yet that would be helpful

Genetics are vital for understanding the evolution and domestication of horses and cattle. In recent years, genetic studies have helped to clarify where, when and how many times cattle and horses have been domesticated, which genes were involved, in the case of the horse and even resolved aspects of the phenotype of the extinct European wild horses. Genetics are also very important for breeding and thus for “breeding-back”. But a lot more research could be done to properly understand the aurochs, wild horse and their domestication. Often on my blog I am forced to engage in wild speculations because the genetic framework of the topic I am writing about has not been done yet. With this post, I want to give some impulses for genetic research not done yet that would be very useful for the topic of “breeding-back”, the aurochs and European wild horses.

 

- Resolving more coat colour loci and alleles in cattle. Many of the colour alleles in cattle are hypothetical, because the genetics of cattle colours are not as well-resolved as in dogs or horses for example. Thus, a rigorous study resolving many of the common cattle coat colour alleles would be fine, f.e. one that resolves the allele that is responsible for the recessive lack of red pigment in Podolian cattle, Tudanca, Grauvieh and Chianina, or the allele(s) that remove the rest of the pigments in the hair of Chianina. Resolving these recessive alleles and developing tests for those alleles would greatly help to remove them from “breeding-back” populations. 

- after that, testing the colour alleles in aurochs DNA samples. Studies have been done that resolved the colour genotypes of predomestic wild horses, which also revealed some surprises (f.e. that the leopard spotted complex was found in wild horses). It would be awesome if the same would be done with DNA samples from the aurochs. It could reveal surprises too. 

- Researching how many loci were affected in the domestication of the aurochs. That’s surely not an easy task, but it would be very interesting to know on how many loci aurochs and cattle differed, and if there are differences among cattle breeds. Some cattle breeds might differ from the aurochs on fewer loci than others.  

- Finding some key genes that had a role in the domestication of the aurochs and resolving the alleles. This has been done for horses in a recent study, it found two genes that probably had a key role in the domestication of the horse. The same could be done with cattle and aurochs. This would also be helpful for recreating the aurochs or at least creating an aurochs-like animal with the CRISPR-Cas9 method. 

- Studying the genetic background of the sexual dichromatism in Bos primigenius. It would be very interesting to know which loci and which genetic mechanisms are responsible for the sexual dichromatism seen in aurochs and cattle. Identifying individual alleles that are responsible for the well-marked dichromatism seen in the aurochs would also help to select for this trait in “breeding-back” cattle. 

- Resolving some genes involved in horn size and curvature. Currently, only two loci involved in the production of bovine horns are identified, the Polled locus and the Scurred locus. They only determine if the individual is polled or not and if the horns are scurred or not. But the genes involved in horn size and curvature are not studied. Horn size is likely a quantitative trait, but maybe there are one or a couple of loci that have a particularly large impact on horn size. Curvature is probably polygenic as well. If some loci involved in those two traits are resolved, the alleles found in the British aurochs of which the genome has been resolved in 2015 could be checked and traced down in living cattle, what would making selecting for aurochs-like horns much easier than it currently is. 

- Examining the Y chromosome of the Konik pony. So far, only the mitochondrial genome of the Konik pony has been examined. As domestic horses have a very limited Y chromosome diversity, finding unique haplotypes would be a strong hint for recent wild horse introgression, which would be the case if the Konik myth would be true. This, however, is very unlikely and it would be very nice to have it confirmed that also on the Y chromosome the Konik is a usual, robust domestic horse and not a surviving wild horse or a recent wild horse descendant.

- Resolving haplotypes in predomestic European wild horses and trying to trace them down in domestic horses. This would help to clarify how much wild horse introgression into the domestic horse gene pool there was in Europe, and also which breeds might have more influence from native European wild horses than others. 

- Testing European wild horses for the dun allele. So far, the dun locus was tested only for two Siberian wild or ancient horses, which is a way too small sample size to tell us about the frequency of the respective alleles. Also, the locus was not examined in European wild horses, so that we do not know with certainty if they were black or black dun. 

 

 

That Nei distance chart

In 2015, Rewilding Europe published a PDF with a Nei distance chart showing the purported distance of 34 European cattle breeds to the one resolved aurochs genome. Many thought that we finally know which cattle breeds are genetically closest to the aurochs. But interpreting the chart that way would be a huge oversimplification and, in my opinion, inacurrate. In fact, I think we do not know anything more now than we knew before the Nei distance chart. With this post, I want to give my reasons for why I think that. Mind that I am not a geneticist, so this is completely my own interpretation. Critique is much appreciated.  

The Nei distance chart published by Rewilding Europe

1. The Nei distance analysis looked at only a very small fraction of the genome 

 

The cattle genome has 3 billion base pairs, the Nei distance analysis looked at 700.000 base pairs. Precisely, the analysis studied single nucleotid polymorphisms (SNPs). 700.000 SNPs is certainly a lot, but only a very small fraction of the total genome, thus it does not tell us much about the genetic closeness of the cattle breeds to the aurochs. With another 700.000 SNPs the results could be completely different. 

 

 

3. Only one aurochs genome was used for the analysis 

 

We have only one resolved complete aurochs genome for now, which is a problem for trying to analyse the genetic closeness of cattle breeds to their wildtype. It is unlikely (or actually impossible) that one individual comprised the full genetic diversity found in the wildtype populations, thus there must have been wildtype alleles found in other aurochs but not found in this one particular individual. The problem is that these wildtype alleles would be considered domestic alleles if found in a modern cattle individual and not found in the one aurochs individual that had its genome resolved. It could be the case that Caldela, a breed scoring very low on the chart, actually has a lot of wildtype alleles that just happen to be from other aurochs individuals than that of the one genome that we have, and so it results scoring low in the chart. That relativizes the relevance of the Nei distance analysis considerably. 

 

4. Nei distance might not be the ideal tool for analysing the situation of aurochs and cattle 

 

The Nei distance was developed for populations that diverged by mutation and genetic drift in isolated populations. But this is not the scenario that happened in the case of aurochs and cattle. In the domestication of cattle, we have at first drastic genetic bottleneck (since modern domestic cattle go back to only about 80 female founders), then massive directive selection (selection on tameness and economic value) during which many wildtype alleles might have been lost and mutated (= domestic) alleles became fixed, then we have local introgression from different types of aurochs in different regions of the world into the cattle genome (in Africa and Europe at least). Not to forget the not uncommon intermixing between taurine and indicine cattle, which descend from two rather divergent aurochs subspecies. 

 

That is why I have covered the Nei distance chart in only one post on my blog till now. I think it does not tell us much about the actual genetic distance between the aurochs and domestic cattle breeds. That is why the score in the chart seems to be rather coincidental and there is no correlation between a less-derived phenotype and the purported genetic closeness to that one aurochs individual analysed in the chart. For example, Fleckvieh scores higher than the Spanish fighting bull. Of course, it can be possible that a breed that has a rather derived morphology shares more alleles with the aurochs than one with a less-derived morphology, since many of the differences between aurochs and cattle might be non-visible, for example immunology, development, endocrinology, neurology, metabolism, or physiological aspects. But I consider it highly unlikely to be the case with Lidia and Fleckvieh, because Fleckvieh has experienced far more intense selective breeding than the Spanish fighting bull. Their score in the Nei distance chart is not evidence for that either, as outlined above. 

Furthermore, which aurochs are “the aurochs”? Even if we only care about the primigenius subspecies it is complicated to give an answer to that question. British cattle landraces have been found to share nuclear alleles with the British aurochs, likely due to introgression, which we cannot expect for Iberian, Italian or Near Eastern breeds and vice versa. 

Also, the total genetic closeness to the aurochs does not tell us which alleles are present in which breed, which is crucial information if one wants to unite aurochs alleles in one population with selective breeding. A breed scoring low in the overall genetic closeness to the aurochs might have alleles which all the other breeds do not have, and this is exactly the case in this Nei chart: Nelore, as an incidine breed, will share alleles with the British aurochs which taurine cattle have lost, because this is what was found by Orlando et al. 2015 (by the way, if the Tauros Programme is indeed aiming for breeding for “aurochs alleles”, why aren’t they breeding with zebus? There is no other way to get these alleles into the population. The answer is: Because they are not breeding on a genetic level, contrary to what they claim in press releases…). 

Thus, I think that this Nei distance chart does not tell us anything of value for “breeding-back”. Why did the Tauros Programme conduct this analysis, then? I think that’s because they needed to publish something “genetic”, in order to back up their claims that they are breeding for aurochs-like genetics. The project was very content with the results of the chart. They claimed that the breeds used in their project were particularly high-ranking. As you can see in the chart (the Tauros Programme breeds are those written in bold), this is not necessarily the case. Their breeds seem to be rather evenly distributed along the chart. However, this is not relevant for “breeding-back” anyway, at least in my opinion, for the reasons outlined in this post. 

 

Literature

 

Orlando, L.: The first aurochs genome reveals the breeding history of British and European cattle. 2015. 

 

Heck cattle at Oostvaardersplassen develop aurochs-like horns

I have made a couple of posts about the possible changes in horn shape in the Heck cattle in the Oostvaardersplassen reserve. Recently, I found some new photos of a group of young bulls in the reserve that all show interesting horns from March this year. You can see the animals here. 

Not only are the horns interesting, the bulls are also much more long-legged and less massive than Heck cattle found in zoos (which is were they descended from). Morphology can be influenced by phenotypic plasticity, so these changes in body shape and proportions do not necessarily indicate a genetic change in these cattle. In the case of the horns, however, I see no way how phenotypic plasticity can influence the horn curvature and orientation relative to the snout, thus I think we see genetic changes here. A change in allele frequency as a result of natural selection is the population genetic definition of evolution. Thus, we might see evolution at work here. 

In how far are the horns of these young bulls different? For once, they face clearly forwards in a 70 to 60° angle relative to the snout, which is identical with the horn orientation of the European aurochs. Earlier Heck cattle from the reserve (which can be seen on older photos easily available on the internet) never have forwards-facing horns, at least not on the photos I have seen so far, which are quite a lot. Furthermore, while the horns of early Oostvaardersplassen Heck cattle are curved rather straight, the horns in these bulls are curved more clearly. They do not curve inwards as strongly in the aurochs by far, but a tendency of the horn tips to grow a curve is there. This can also be seen, even more clearly, in some of the cows in the reserve (the photos aren't online anymore, unfortunately). To me, this suggests that the horn shape of the Heck cattle in the Oostvaardersplassen reserve is evolving. Precisely, evolving to a more aurochs-like horn shape. 

This is not surprising, as the horn shape of the aurochs probably had a purpose. Their strong inwards-curve enabled the bovine to push and pull the opponent during a fight, and the fact that they faced forwards and not upwards or downwards was likely functionally advantageous as well. If the horn shape of the Heck cattle in the reserve is indeed evolving, which can only be proven by gathering photos of individuals from the early years till today, it would endorse the following thoughts: 

1. the horn shape in cattle/aurochs has a function and the horn shape of the aurochs was not a coincidence

2. This has an impact on the evolutive fitness of the individuals (the more functionally advantageous the horn shape the higher the likelihood to win an intraspecific combat for breeding rights, feeding grounds etc.)

3. Eventually, the wildtype horn shape will develop in a cattle population that is exposed to natural selection, especially intraspecific selection 

The more genetically diverse the population, the faster the changes evolve (Fisher's fundamental theorem). Since Heck cattle is a mosaic breed based on many different cattle breeds, the wide range of phenotypes displayed by the individuals might have enabled the adaption process to become visible quite fast. 

I postulated that natural selection will make a variable cattle population in the wild more aurochs-like because wildtype traits are functionally advantageous multiple times on my blog, and I think these recent photos of Heck bulls at the Oostvaardersplassen reserve endorse this idea when you compare them with earlier individuals of the same population. In my opinion, the Heck cattle at this reserve are a valuable example for dedomestication. 

It is no secret that the original founding population of the Heck cattle at the Oostvaardersplassen, being ordinary Heck cattle from various locations, were not prime examples for aurochs-likeness. Yet, natural selection produced at least partly aurochs-like horn phenotypes after 40 years of intraspecific competition. This fits my idea that natural selection will "refine" any "breeding-back" product once released into the wild - if it worked on the mediocrely aurochs-like founding population of Oostvaardersplassen, imagine what kind of phenotypes might be produced by 40 years of natural selection with more aurochs-like cattle. 

Which horses should be used for a reintroduction in Europe's nature?

The discussion which horse breed or type is closest to the European wild horse and which horses should be used for a reintroduction of the species into European nature systems is sometimes carried out rather controversially and is sometimes needlessly emotionalized. In recent years, a variety of horse landraces have been used for “rewilding”, including the Konik pony, the Exmoor pony, the Garrano pony, the Hucul, Retuerta, Sorraia and the Bosnian Mountain horse. Some of them have popular background stories that claim they are, respectively, the most recent descendants of the European wild horse – none of these popular background stories are scientifically tenable. That does not make those breeds any more, or any less, suitable for natural grazing projects or even establishing truly feral populations. The Konik pony and the strongly Konik-influenced Heck horse are most frequently used in natural grazing and “rewilding” projects, probably due to their scientifically untenable reputation of being wild horses, recent wild horse descendants or phenotypic copies of the European wild horse. However, the range of pony or horse breeds used in “rewilding” is slowly diversifying. Currently, the only place in Europe where horses live completely free of human influence (except for poaching, unfortunately) is the Chernobyl exclusion zone, where a population of about 100-200 Przewalski’s horses thrives. They also happen to be true wild horses instead of domesticates. But which type of horse should be used for a reintroduction of Equus caballus into European wilderness?

One of the problems we face when trying to resolve that question is, apart from all the confusion that the mythologized breed origin stories of certain landraces have created, that we do not know how the wild horses in Europe exactly looked like. Not a single complete skeleton of a Holocene, predomestic European wild horse has been described so far. It is likely that it had the robust pony morphology with a thick head, as this morphotype is found in the closely related Przewalski’s horse and Pleistocene wild horse skeletons from Europe. But we do not know the morphology for sure. What is much more certain is the colour phenotypes, as the colour loci of ancient DNA samples from European wild horses have been tested for the respective alleles. It turns out that during the early and middle Holocene, both bay dun (the colour of the Przewalski’s horse) and black dun (the colour found in Koniks, Hucule and Sorraias) were found in European wild horses. During the later Holocene, however, black dun became the prevalent phenotype as a//a is the prevalent genotype found in the ancient samples [1]. It is also possible that non-dun wild horses existed in Europe, but the Dun locus has not yet been tested in European wild horse samples. I believe that it is likely that dun was prevalent (go here). A tricky question is the mane of Holocene European wild horses. All wild equines today have a standing mane, while hanging manes are found exclusively in domestic horses and donkeys. Nowadays I think it is much likelier that European wild horses had a standing mane as all other living wild equines do (go here for a post). 

It is also important to note that there was not one European wild horse during the Holocene, but at least two subtypes: Iberian wild horses and wild horses on the rest of Europe. It turns out that, genetically, Iberian wild horses are less closely related to the ancestors of domestic horses than the Przewalski’s horse [2]. Furthermore, it is important to note that the range of wild horses was likely continuous from Europe to Asia and that there was a continuum between European wild horses and the Asiatic Przewalski’s horse, as introgression from the latter subspecies has been found in a European wild horse stallion’s DNA sample [3]. 

 

Combining these facts, there are two concepts for horse reintroduction in Europe that I prefer. I cannot decide which one of the two concepts I favour as both have pretty strong pro-arguments. I see that there are diverse options for “rewilding” horses on this continent and that each project is free to pick those types of horses they prefer, but I think there should be a somewhat consistent baseline for why choosing a particular breed for a true reintroduction into European nature, at least in my opinion. By true reintroduction I mean the establishment of self-sustaining, unregulated horse populations in a nature system or wilderness area. 

 

1. Using pure Przewalski’s horses 

 

There are two very obvious arguments for choosing Przewalski’s horses exclusively for the reintroduction of horses into Europe’s nature. For once, they are the only wild horses left. It is true that the Przewalski’s horse is the Asiatic subspecies, and therefore not the native subspecies, but it has to be considered that it is closer to European wild horse subspecies outside Iberia than the Iberian wild horse was, and that there apparently was a continuum between both subspecies. Furthermore, it is very likely that the Przewalski’s horse would have recolonized the European continent after the man-made extinction of wild horses in Europe if it had not been for human influence. It is true that the habitat of the Przewalski’s horse was restricted to the steppe in historic times, but we do not know the natural plasticity of the ecotype as it might have also inhabited other biomes previously. Przewalski’s horses do very well in grazing projects in Central and Western Europe and also wild in the European wilderness as the Chernobyl population demonstrates. The second argument for using Przewalski’s horses exclusively is that it would be a very valuable contribution to the preservation of this endangered last remaining wild horse subspecies. The Konik population in Oostvaardersplassen numbers around 1000 individuals – image Przewalski’s horses would have been chosen for that initiative. It would have grown to the largest single Przewalski’s horse herd on the continent (or perhaps even the entire world). There are dozens of grazing projects in Germany alone, if all of them chose Przewalski’s horses instead of domestic horses it would not take long until the last wild horse on this world is not endangered anymore. 

The question then is, why are not all “rewilding” and grazing projects using the Przewalski’s horse? This has two very practical reasons. First of all, the Przewalski’s horse is not just another domestic breed, but a genuine wild animal with the behaviour of a wild animal. They can be very aggressive, particularly the stallions, and may attack humans. Przewalski’s horses are very difficult to handle. The other reason is that Przewalski’s horses are not as easily available as domestic breeds are. 

 

2. Using hybrids of Przewalski’s horses and robust landraces 

 

The second concept is using hybrids of Przewalski’s horses and robust landraces that are adapted to the climate and vegetation of the respective region. The reason for that is that European domestic horse breeds are the descendants of the European wild horse, and thus there is a chance that they preserve at least some of the wildtype alleles that were unique for this wild horse type. The Przewalski’s horse should be in the mix because it is a wild horse with a wildtype morphology, genetics and behaviour. This would also create a greater genetic diversity than using Przewalski’s horses only, as they have a limited genetic diversity due to their genetic bottleneck during the 20^thcentury. As a continuous range of free-roaming horses from Iberia to Asia is illusional in modern times, there is no danger of intermixing between pure Przewalski’s horses that have been released back into the wild and the hybrids in isolated European reserves. 

Creating hybrid populations of Przewalski’s horses and robust domestic landraces is also the chance to mimic the phenotype of the European wild horse. As mentioned above, the exterieur of that wild horse type during the later Holocene likely was the pony morphotype coupled with a standing mane and the black dun coat colour. The Przewalski-Konik hybrids living in the Lippeaue (go here or here) bear great potential for achieving that with selective breeding. The recessive standing mane and the recessive black dun coat colour can be fixed rather easily by breeding. I do not necessarily suggest that the combination Przewalski-Konik is the way to go for entire Europe. Many local landraces could be crossbred with Przewalski’s horses for “rewilding”. For example, the already established populations of Garranos, Sorraias, Exmoor ponies, Hucule and Bosnian mountain horses could be supplemented by single Przewalski’s horses, most ideally stallions. Surplus animals from zoos could be used so that the population of Przewalski’s horses that is used to preserve the subspecies is not depleted. And as the Lippeaue horses have shown, the introgression of one single animal can have a great impact on the phenotype of the entire herd without affecting Przewalski’s horses preservation efforts. I would pay attention that the genes for a black dun coat colour are always in the mix, as this was the original colour of the late Holocene European wild horse. In the case of the Sorraia, Hucule and Bosnian mountain pony, these alleles would be in the mix. In the other breeds, it might be best to introduce black dun stallions with a standing mane from another location to produce the desired phenotype. 

 

I think Przewalski’s horses should always be in the mix because they represent the last wild horse and the populations in Chernobyl and grazing projects have shown that they do well in the European biome. Alas, most projects will likely pick domestic horses only, because they are easier to handle, easily available, cheaper and there are no legal restrictions. 

 

Literature

 

[1] Sandoval-Castellanos et al.: Coat colour adaptation of post-glacial horses to increasing forest vegetation. 2017.

[2] Fages et al.: Tracking five millennia of horse managment with extensive ancient genome time series. 2019. 

[3] Wutke et al.: Decline of genetic diversity in ancient domestic stallions in Europe. 2018. 

 

 

Video of a Steinberg/Wörth bull and Tauros cattle

The video above shows the bull Azrael, which is currently the breeding bull at the Neandertal Heck cattle herd. The Neandertal herd was important for improving the quality of non-crossed Heck cattle in the 20th century, as they included a half-Watussi cow in the 1960s and used her 25% Watussi son as a breeding bull. This created good horns in the herd. The Neandertal Heck herd was also important for the Steinberg/Wörth lineage, as many of its founding individuals were from that herd. The Steinberg/Wörth lineage is the Heck lineage with the most aurochs-like horns among the breed, due to consequent selective breeding. Now (at least in 2020) the Neandertal herd has a breeding bull from the Steinberg/Wörth lineage, what is certainly useful for maintaining the good horns in the herd or even improving them. Azrael has large and thick horns, matching those of many aurochs skulls in dimensions. 

This video shows a group of individuals of the Tauros cattle herd at Keent, the Netherlands. The bull is certainly part Maremmana, as the horns, diluted coat colour and large dewlap reveal. I like the body morphology of the bull, as the trunk is not too long and the body not too heavy. Also, the hump is large. If it had good horns and the right colour, it would make a good breeding bull. The sexual dichromatism seems to be completely absent in the herd, as the cows are dark while the bull has a saddle (the opposite of what should be the case). The individuals are called "Taurus cattle" in the video title, which is wrong as they are Tauros cattle. Those two names will be confused forever, and many even think Taurus and Tauros cattle are one and the same because the names are so similar. I wonder why the TaurOs Programme picked a name that is so similar to an already existing project/breed. 

My trip to the Lippeaue in 2022 (Taurus cattle)

Last week I visited the Lippeaue reserve again, which is the main Taurus cattle breeding site in Germany. As usual, it was a very enjoyable trip, and it was great to see the animals again and how the herds progressed since 2017. 

It has been five years since my last trip to the reserve in 2017. Some of the older individuals have died or had to be slaughtered in the meantime, including Lerida, Dona-Urraca (the Sayaguesa cow with the great horn curvature), Linnet and the huge Laokoon’s brother. Others, like Lamarck, are still in the herd. The other current breeding bulls are new. I counted 98 individuals in the stock list, including the calves. As long-term readers of my blog will know, the Lippeaue population is divided into five herds: Hellinghauser Mersch, Klostermersch-Nord, Klostermersch-Süd, Disselmersch and Kleiberg. There is one breeding bull per herd, selection takes place by picking a breeding bull with desired traits and selecting out individuals. 

 

Hellinghauser Mersch 

 

The current breeding bull at Hellinghauser Mersch is a nameless bull with the number 47 938, which is the son of Laniel and Larissa. Therefore, both its parents are crossbred themselves – this is good, because it’s where the real selective breeding starts. 47 938, as a result of two crossbred individuals that both are very useful, looks good itself. He has a flawless wildtype colour, horns facing forwards in a 60° angle to the snout, the hump is more or less large, and he has a short dewlap. He is three years old, thus not fully grown. 

 

The cow 42 604 is one of my favourite cows. I saw her as a young cow in 2013, and her horns developed considerably since then. Her colour is a flawless aurochs cow colour, and bears striking resemblance to some of the depictions at the Lascaux cave. She is a daughter of Lamarck (Sayaguesa x (Heck x Chianina)), and Julia, a red Sayaguesa cow, thus she is 75% Sayaguesa. In general, Sayaguesa is by far the dominating breed in the Lippeaue gene pool. This is because Sayaguesa simply is a very useful breed that results in good-looking animals. 

 

Another good cow of the same combination but with a different Sayaguesa mother (named Zamora) is 42 630. Like 42 604, she has a perfect wildtype colour and her horns are good as well. 

 

Apart from the wildtype-coloured individuals, there are some other colours as well. There is the cow 55 443, which is one of those with a pink nose and a light coat colour. I think that it is possible that it is the e mutation on the Extension locus, a colour variant that is found in breeds like Highland and Simmental, but I am not sure. This mutation disables the production of black pigment in the mucosa, horn tips and coat colour and is recessive under the wildtype allele. I wonder which breed contributed the colour variant displayed by 55 443, perhaps Heck cattle (Highland is one of the founding breeds of Heck). Basically, it is tried to avoid this colour variant, but 55 443 has good horns and is comparably large, so she is kept in the herd. She is the daughter of Laokoon’s brother (Sayaguesa x (Heck x Chianina)) and Loren, a daughter of Luca and Lirgit. 

 

Another cow with a deviant colour variant is 47 988. Her nose is pink too, therefore she might have the e mutation too, but she also seems to have dilution alleles contributed by Chianina. She will be selected out. 

 

One of the Lidia-influenced individuals is 79 813. She is the daughter of Lamarck and Lepisma, a half-Lidia cow. She is a little bit more nervous than other cows, which is very likely due to the Lidia influence. Her horns are good, the colour is alright as well, and she is from good parents. 

 

Most of the bulls that are born in the Lippeaue are black with a dorsal stripe. Some, however, have a saddle. And a young bull in the Hellinghauser Mersch this year is kind of cow-coloured. He is a son of Laokoon’s brother. I suspect that this is the case because Laokoon’s brother had a saddle, so that the sexual dichromatism is less pronounced in some of the individuals in this herd. 

 

55 444 is another cow with a flawless aurochs cow colour. 

 

Klostermersch-Nord

 

Lamarck is an old boy now, he is 15 years old. He still looks good, he did not grow a massive body. I think his horns even grew a little bit. I still consider Lamarck the best Taurus bull to date, and therefore the best “breeding-back” bull that was born yet, although he is not as huge as Laokoon’s brother. Due to his age, he has become slow and tired, often he is found outside the herd. It’s probably his last year. 

 

Linea is of the same combination as Larissa, namely Chianina x (Sayaguesa x (Heck x Chianina)). She is the daughter of the Chianina cow Eloisa and Lombritz. As she came rather close, we tried to measure her withers height, and the result was 156 cm. For a cow that’s a very good size, most aurochs cows were not much larger. 

 

01 896 is a daughter of Laokoon’s brother and Dunja, so it is an F2 of the combination Sayaguesa x (Heck x Chianina). I think true F2 are very interesting, as they have a higher chance to be homozygous than usual crossbreeds.  

 

55 441 is the daughter of Lamarck and Nadia, the Heck cow from the Steinberg/Wörth lineage, so she is half Heck half Sayaguesa x (Heck x Chianina). 

 

Nadia herself is old now and doesn’t calf anymore. She bore two bull calves which were slaughtered and 55 441. 

 

Klostermersch-Süd

 

Most of the individuals on this photo have the right colour for their sex, so there is good dichromatism in the herd

The breeding bull at Klostermersch-Nord is Laniel. He is the son of the Sayaguesa cow named Augustina and Laokoon’s brother. The horn curvature is really nice and also the hump is comparably large, what compensates the fact that he has a faint saddle. 

 

01 870 is a daughter of Laokoon and Laniana, therefore she has a little bit Lidia in her blood. The colour is flawlessly aurochs-like, and also the horns are good. 

 

Larissa next to a wildtype coloured cow

Larissa is the largest cow in the Lippeaue and the same breed combination as Linea, with the Chianina mother Laura. 

 

Disselmersch

 

The breeding bull at Disselmersch is Darth Vader III, who became famous as the “jumping bull” on Youtube. He is the son of Londo, who was an F2 Sayaguesa x (Heck x Chianina) and the son of Lamarck, and the cow Laniana. He is 1/32 Lidia. 

 

Guessing by eye, the body size and horn size of the animals at Disselmersch is slightly smaller than in the other herds. 

 

Kleiberg 

 

Linnet was replaced as a breeding bull this year, the new breeding bull is Dominator. He is the son of Laniel and a Sayaguesa cow, therefore mostly Sayaguesa. The horns of this bull are great. The curvature is very aurochs-like, and if they continue growing with this curve they will be perfect. The angle between the horns and snout is rather narrow, but that will be compensated by the horn orientation of other individuals. The horns also have a nice size. He will continue to grow for a couple of years, I am looking forward to see how large he is going to get. 

 

Bionade, the Sayaguesa x Chianina cow, is alive and well. Back in 2017, I measured her at 155 cm at the withers, and she must have grown since then, because she is huge. She came rather close, and I was impressed by how large she is. I am looking forward to the offspring with Dominator, his great horns coupled with her large size surely has a lot of potential. 

 

Another very large cow is Kasmerodia. She has the same deviant colour as 55 443 which might be the recessive e mutation, but her large size and the large horns make her a useful individual. She is the daughter of Loren and Laokoon’s brother, therefore she is more Heck than Sayaguesa yet still she is huge. That shows that genetics work by chance, which is always interesting to see. 

 

Kalandra is a daughter of Linnet and Kalidis, a daughter of Bionade. Her horns are comparably large and the colour is aurochs-like. 

 

The most important question is: did the average quality of the individuals increase over the last few years? I think it did, as cows with inwards-facing horns are now much more common than in 2017, 2015 or 2013. Looking at the horns of most of the individuals, the first impression may be that the tips should face more inwards, but actually the curvature is alright, it is just that they should be oriented a bit more diagonal when viewed in frontal view. To explain what I mean, have a look at the photomanipulation of Lerida. I elevated the horns laterally by a few degrees in the "aurochs picture". Maybe it is best to call this the “lateral horn orientation”, in contrast to the horn orientation relative to the snout. I haven’t realized that this is a factor previously. Once the horns are a bit more laterally elevated, the curvature automatically looks more aurochs-like because the tips face more inwards, although the shape of the horns is actually the same. That way, the horns would resemble those of a lot of aurochs skulls, such as the one from the Gramsberger Museum or that at Asti, Italy. I don’t know how to fix that by breeding in future generations, as many aurochs-like landraces have a horizontal lateral horn orientation. All in all I think the horn curvature of most of the individuals is good and has improved over the last years. 

Regarding the sexual dichromatism, most individuals are coloured correctly. Bulls tend to be black with a dorsal stripe, cows tend to be reddish brown. However, there are also black cows and rarely also cow-coloured bulls, so that the dichromatism is often present but not always. 

Concerning the general colour, most individuals have the right colour phenotype. Half-Chianina individuals have a diluted colour of course, as Chianina has several dilution alleles, some of which are recessive. Selective breeding has to purge these alleles from the population in the long run, but considering that colour is regulated only by a few genes, that’s not all too difficult. 

Regarding the morphology, I think the trunk of the cattle is longer than in the aurochs. This is a general problem for “breeding-back”, no matter which project, as in most taurine cattle the trunk is longer than in the aurochs. Only some zebu landraces have a truly aurochs-like short trunk. This is why I included trunk length in my list of the challenges for “breeding-back”. But in general, Taurus cattle are of course more long-legged than Heck cattle, and also slenderer. 

 

All in all, I think the herds are on a pretty good way. I like all of the current breeding bulls and I am looking forward to see how large they will get and what the horns of Dominator are going to look like when he is fully grown in a few years. I was very impressed by the size of Bionade, Kasmerodia, Linea and Larissa. The horn size of many individuals is within the range of the Holocene European aurochs when skeletons like the Himmelev bull are considered. Of course, hypothetically, crossing-in Watussi for example would increase the horn size but it would also introduce a lot of unwanted traits like a large dewlap, the indicine hump, or a small body size. Backcrossing with Chianina would help to increase the body size, but also increase the frequency of alleles for small horns and colour dilutions – therefore, it is always about finding the right balance and prioritizing certain traits. Otherwise, it would be too easy. 

So far, no individual has been born that comprises all of the desired traits (that goes for all the other “breeding-back” projects as well of course). But I think that basically all of the aurochs traits that are achievable with domestic cattle are present in the gene pool, therefore the first of the milestones for “breeding-back” that I have defined years ago has been accomplished in the Lippeaue.

 

The horses 

 

The Lippeaue reserve is also home to the Konik-Przewalski crosses. These are either bay dun with a standing mane as a Przewalski’s horse, bay dun with a falling mane and rarely also black dun with a standing mane. Most individuals are bay dun in colour because they are most likely heterozygous and the a allele on the Agouti locus (resulting in black dun) is recessive under the A allele (resulting in bay dun), therefore bay dun is the dominant phenotype of most of the crosses. So far, no concrete breeding goal for the phenotype of the crossbreeds has been defined. They are wilder in behaviour than Koniks, which are domestic horses, since Przewalski’s horses, being wild horses, are more difficult to handle than the domesticates. The remaining pure Koniks are sometimes sold as riding horses, which is impossible with the Przewalski’s hybrids because of their wild behaviour. Interestingly, I was told that the legal protection status of the Przewalski’s horse in Germany also goes for the hybrids, what surprised me. Some of the hybrids have already been sold to other grazing projects. This could increase the Przewalski’s influence in the Konik in Germany (the Konik already has introgression from the Przewalski’s horse) in the long run, which I consider a good thing. A haplotype typical for Przewalski’s horses has been found in an ancient DNA sample from a European wild horse stallion, what suggests that the range of the two subspecies was continuous. Therefore, Przewalski’s influence in European landraces is not “unnatural”, and also beneficial because the Przewalski’s horse is a genuine wild horse. In the end, the Przewalski’s horse would likely have recolonized Europe from Asia after the extinction of the European wild horse if it had not been for the anthropogenic obstacles. 

All in all, I think the Taurus cattle in the Lippeaue represent the top-level of current "breeding-back", and also the Przewalski's hybrids are very interesting and have potential. Therefore, it is always great to visit the herds and see the breeding progress.