Setting milestones for "breeding-back"

Now, in 2017, there are many different aurochs projects (Taurus cattle, Tauros Project, Uruz Project, Auerrind Project) and Heck cattle is still a very heterogeneous pool but slowly increasing in quality. More and more nature areas become free for natural grazing by large herbivores and the numbers of aurochs-like cattle is rising with each year. So it is maybe time to speak about the milestones of "breeding-back". What is the goal, and when can we consider it achieved?

In my previous post I explained why I think selective breeding with domestic cattle cannot deliver something that is a true aurochs in the strict sense of the word, but at least something that comes morphologically, ecologically and behaviourally very close. The ideal state is having these cattle living independently in the wild as wild animals, and successively having their genome shaped by nature. This is the final goal and it will take its time until it is reached. But I think there are several milestones for “breeding-back” that I want to outline here.

1. Creating a population that contains all achievable aurochs-like traits

Prior to “breeding-back”, there was no population of modern cattle in which all achievable aurochs-like traits were found. That is why “breeding-back”, no matter which project, has to rely on crossbreeding a set of breeds in which each breed contributes one or more desired traits (be it morphologic, ecologic et cetera). By doing so, you create a heterogeneous cross population that also contains a lot of undesired traits. It is the goal of selective breeding to get rid of those undesired traits, but before you can do that, all aurochs-like traits have to be present in the population in order to achieve a result that is as authentic as possible. We probably cannot achieve 100% perfect copy of the aurochs working with modern domestic cattle (for details, see here), but something that is very close in many aspects. That is why I speak of all achievable aurochs-like traits instead of all aurochs-like traits.

Taurus cattle, both the population at the Lippeaue and Hortobagy, have achieved this milestone. You can find all the desired achievable traits (accurate colour, body size, horn size, horn curvature, sufficient body shape, sufficient snout length, sufficient sexual dimorphism [more on that in a future post]) in both populations respectively. To give an example, forwards-facing horns are prevalent in the Lippeaue herd. Inwards-facing horn tips are present, but only a few individuals. Selective breeding has to fixate this trait in the population, and therefore get rid of the individuals with insufficient horn curvature. The same with snout length: some cows and bulls show an aurochs-like long snout, the challenge is to fixate it in the population.

As for the Tauros Project and the Auerrind Project, it might be too early to judge yet. For the Tauros Project, I fear that they will need some boost in horn volume and body size (for the latter, there is no data, however). The breed choice of the Auerrind Project should contain most of the achievable aurochs-like traits, the crossbreeds that will be born in the future will show how well traits such as sexual dichromatism and inwards-curving will work out horns work out. For the Uruz Project, there are no publicly known cross herds for now, so that I cannot say much yet.

2. Uniting all achievable traits in one individual

The next milestone would be to unite all the aurochs-like traits that are present in the population in one animal at least. This is a milestone that has not been reached yet. Of course the judgement is also a bit open to one’s preferences, as we cannot directly compare the individuals to living aurochs. For example, I think that the Taurus bull Lamarck and the Taurus cow Lisette are rather close to the goal already. But Lamarck’s horns could be more curved, the snout longer, the body still more athletic and probably also the legs slightly longer. And maybe I am picky, but I think Lamarck would also need more frizzy and curled forelocks in order to achieve "perfection" regarding aurochs-likeness. Lisette looked great overall, but her horns could have been larger and more curved, she was small overall and had white spots on the belly (how much does that matter? More on that in a future post). My choice of those two individuals as examples for very aurochs-like cattle is more or less subjective; there are many good individuals, also of pure breeds. Many Corriente and Lidia are rather close to what I consider the achievable maximum, but with noticable deficiencies (in those two breeds it is primarily the lack of body size, for example).

So we still need a bit patience and luck until the first individual that really displays a maximum of aurochs-resemblance that is possible. Furthermore, there will probably be no universal agreement on what actually is a perfect maximum of achievable aurochs-likeness. Different people also have different priorities.   

3. Getting rid of the undesired traits and create a stable population

When the first universally satisfying animals are born, the next challenge of selective breeding is to fixate this genetic make-up in the whole population. That means to finally exterminate the last undesired traits and create a truly homogeneous, aurochs-like population.

Cattle are a slowly reproducing species, and therefore it will take its time, probably several decades, until number 3 is achieved – especially since some projects, such as the Auerrind Project, have just started yet, and the Tauros Project is in the beginning phase as well. Some methods have been discussed on the web to speed up the process, including breeding schemes based on “true Filial crosses”, but it is important to maintain a certain amount of genetic diversity at the same time, as this is crucial for the populations health and adaptability.  

4. Releasing the animals and letting them evolve into a wild animal

Cattle that live and reproduce independently under natural circumstances without the need of veterinary care and supplementary feeding are the goal of all of the projects anyway, as they mostly serve a conservational purpose with the cattle as grazing tools. And for “breeding-back”, the goal of maximum authenticity has to be a truly wild animal at some point, as the aurochs itself was a wild animal per definition. That’s why I wrote

“If ‘breeding back’ aims to approach the aurochs as closely as possible, the result has, ultimately, to be a wild animal.”

in 2015. Phenotypical plasticity and natural selection will alter the anatomy, physiology, behaviour, genetics and ecology of the aurochs-like cattle, and chances are good that this will make them even more aurochs-like (see the Dedomestication Series), and after a sufficient amount of time the population can be considered feral, and after that, truly wild. But it will take a very long time, probably centuries, until the selective pressure has altered the genetics of the population enough to speak of a truly wild animal. Nevertheless, we will probably live long enough to see those cattle looking and behaving like wild animals, and they will be suited to their environment.

Especially because the process of dedomestication can run parallel to “breeding-back”. Actually, the cattle of all those projects live in a more or less semi-feral state already in the grazing projects they are used. However, the breeding is still (and has to be) strongly regulated by choosing one breeding bull per herd plus selection. The next step would to let them breed naturally when they reached a satisfying level of aurochs-resemblance (with the competition of several bulls for breeding rights), and influence the population only by the removal of individuals that display too many undesired traits (however, I think this could be a mistake at too early phase, I can explain why). And in the long run, the population can reproduce freely and develop into a wild animal and artificial selection is done only on traits that would otherwise remain in the population for a very long time, such as recessive traits or domestic colour variants.

This is basically the plan that the Tauros Project has presented:

Although I do not think it is realistic that natural selection has enough time to turn the population into truly wild animals by 2025 or any point of this century, most of us will probably live long enough to populations of very aurochs-like cattle living freely and independently and behaving and looking like wild animals.

5. Numerous populations of aurochs-like cattle living in nature areas on the complete Holocene range of the European aurochs

Of course it is one of the goals to reintroduce cattle not only in one or two single reserves, but restore the ecological niche of the aurochs in as many reserves as possible on its former range. Actually, this milestone can be considered reached or almost reached already, just not with the desired very aurochs-like, stable and more or less dedomesticated cattle that are the goal, but the current “breeding-back” cattle that we have. There are “breeding-back” herds in nature reserves in virtually all regions of the European continent, from the Iberian peninsular to the Balkans, from the Netherlands to Latvia.

And once all those herds have reached the four previous milestones, we can confidently say that the niche of the aurochs has been filled as best as possible with domestic cattle until a true revival of the aurochs via genetic methods is feasible and executed (cloning or CRISPR-Cas9).

This is at least the way I would draw a scheme for the stepwise progress of "breeding-back", but I think that many people might see it in a similar way.