There have been such projects in the past. The most widely known "breeding-back" project for horses was that of Lutz Heck in Berlin, Germany, in the 1930s and 1940s. He used a Przewalski's stallion to cover mares of the Dülmen pony, Icelandic horse and Gotland pony, and subsequently mixed the results with Koniks. The resulting Heck horse has been repeatedly crossed with Koniks after the Second World War so that it is virtually indistinguishable from this breed today [1]. The Konik itself is not the result of a "breeding-back" project, but a landrace (see here) instead.
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| A Heck horse mare in the Tierpark Hellabrunn. The Heck horse is a well-known "breeding-back" result with horses. |
Another "breeding-back" project for horses focused on Koniks exclusively. It was that of Tadeusz Vetulani, started in the 1920s. He thought that keeping Koniks in a semi-feral state would re-develop what he considered wildtype traits, such as an upright mane and a white winter coat [2]. Actually, this was more of a dedomestication project rather than selective breeding.
From 1960 onwards, Konik and Fjord horses have been crossed in the Bayerischer Wald, Germany, in order to achieve a more wild horse-like exterieur (or what the breeders considered wild horse-like). The result is called the Liebenthaler horse [1].
In the 1970s, the Wildpark Hardehausen crossed Heck horses with Przewalski's horses again on order to achieve an upright mane [1].
In the Lippeaue, Germany, several Przewalski-Konik crosses can be found. This is not really a "breeding-back" project - a Przewalski's mare was included in a Konik herd, and now there are Przewalski x Konik as well as 75% Konik 25% Przewalski's horses in the herd, and possibly even younger offspring. See here for my post on these horses.
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| A Przewalksi x Konik mare in the Lippeaue |
How about a new "breeding-back" project for European wild horses?
So far, there is no breed that matches European wild horses in "phenotype". Admittedly, the reconstruction of the life appearance of these horses is speculative, but a few things can be inferred. Holocene European wild horses probably were predominantly black at a certain time of their evolution, as genetic studies suggest (see here). Whether their mane was erect as in extant wild equines or falling as in domestic horses is unknown as there are no specimen with soft tissue preserved and no historic descriptions that unquestionably describe European wild horses. But it is not unlikely that they had an erect mane (see here). Concerning the body and its proportions, there is not much known as there are no articulated skeletons that have unambiguously been referred to wild horses in Europe. But in general, a "pony type" with a robust head is assumed for the European wild horse.
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| A reconstruction of the Holocene wild horse as suggested by recent evidence (the mane is still speculative). |
With that in mind, one can dream of a "breeding-back" project for horses with the modern information we have. The breeding goal would be a black pony-like horse with an upright mane. For that, either Przewalski's horses or some of the hybrids of the Lippeaue (as long as they have an upright mane) could be used and crossed with primitive black ponies such as the Asturcon from Spain or black individuals of the Bosnian Mountain pony. Since introgression from the Przewalski's horse has been found in a European wild horse [3], using Przewalski's horses definitely would do no harm. The resulting horse breed can be used as an alternative to Koniks and other horses that are currently used in rewilding projects.
Literature
[1] Bunzel-Drüke, Finck, Kämmer, Luick, Reisinger, Riecken, Riedl, Scharf & Zimball: „Wilde Weiden: Praxisleitfaden für Ganzjahresbeweidung in Naturschutz und Landschaftsentwicklung“. 2011
[2] Tadeusz Jezierski, Zbigniew Jaworski: Das Polnische Konik. 2008.
[3] Wutke et al.: Decline of genetic diversity in ancient domestic stallions in Europe. 2018.
Seeing as Koniks are already black, or rather black-dun, probably the desired result could be created simply by introgression of the the non-dun-1 and bay alleles into the various existing populations. After all, the EWH was not exclusively black, but populations possessed the genetic potential for multiple coat colours, which would be of varying utility in different habitats. So long as the potential is there to select on, I don't think anything like what exists for cattle back-breeding is necessary. Koniks are a perfectly valid breed for base stock, to which diversity can be continuously added.
ReplyDeleteI am aware of the fact that multiple colours have been found in the European wild horse populations; bay, bay dun, black, black dun were probably all present at some point. But if I understand Sandovall-Castellanos et al. correctly, black is the colour that ended up being the only colour found in the more recent samples. I have nothing against using Koniks at a base. The upright mane would have to be fixed by actual breeding however.
DeleteThe study also predates the discovery of the dun factor and, as far as I know, has not been updated since. By the paper's own admission, black-duns are as likely as blacks. I don't think the implication of the paper was that black would become the only colour, only that it would be the most common in certain habitat types. Regardless of where you stand on the naturally open vs naturally closed European habitats question, open habitats would still exist and would still be the preferred habitat for wild horses. In these habitats, bays and bay-duns would still be at an advantage. Certainly many of the rewilded areas where horses are being used these days are not closed habitats and will likely not become so under high herbivory pressure. As for the manes, I'm not sure it's of particular importance. Przewalski introgression will ensure the genes responsible for a standing manes are present. If they confer an advantage, and assuming no loss to genetic drift, they will eventually be selected for. If not, then as long as their manes do not grow overly long, as in some very derived breeds, then I think it's best left alone. Natural selection for less docile animals may even indirectly promote a standing mane if it is indeed the non-domestic state.
DeleteThere was also a response article written about the Sandovall-Castellanos paper that calls some of the results into question
ReplyDeletehttps://pubmed.ncbi.nlm.nih.gov/29459710/
This one touches on some of the same points: https://www.researchgate.net/publication/326615913_Late_Quaternary_horses_in_Eurasia_in_the_face_of_climate_and_vegetation_change
ReplyDeleteThanks for those two papers. They, however, do not question black phenotypes for European wild horses if I understand correctly.
DeleteThe paper of Sandovall-Castellanos et al. was published two years after the identification of the dun factor (which was in 2015 by Imsland et al.). The authors precisely write:
"Considering that all recent equid species are dun diluted, it is likely that post-glacial horses also had this dilution. However, so far our attempts have failed to amplify the dun locus in ancient samples, which is in agreement with a very recent study"
But you may be right that the authors consider dun and black dun equally likely.
Regarding the mane, I agree that having both the genes for an erect mane and a falling mane in the same population would be interesting to see if one of the two conditions is favoured by selection. However, nothing speaks against breeding a strain of black horses with upright manes.
It wasn't the increase in black phenotypes they were questioning, but the cause as I understand it
DeleteHello. This is not related to the article, I just wanted to ask if you happen to be active in Reddit? I have a little subreddit where we discuss topics such as rewilding and back-breeding and your blog posts get posted there quite often. Feel free to come say hi if you haven't already - https://www.reddit.com/r/megafaunarewilding/
ReplyDeleteI feel there is a great difference in the need for breeding back the wild horse and the aurochs. The aurochs did not have a replacement species to fill its niche, but I can’t see why Konik, Exmoor Pony or Przewalski’s horse would be unable to take its place. Given its endangered status, I suppose Przewalski’s horse to be just fine to do the job. Moreover, since we know so little about the original European wild horse, both in appearance and exact ecological place, we will most likely never know if a breeding-back attempt is a succes or not.
ReplyDeleteThough we now consider the Heck Cattle insuccesfull in appearance for a bred-back Aurochs, I must add that this beeing true considering morphological data, I’ve never seen a justification that this makes them unsuitable to fill the ecological niche of the aurochs other than looks-different-so-everything-else-must-also-be-different. At the moment we know strikingly little on the ecological niche of the Aurochs and the difference with the niche of the Wisent. Though I’m quite interested in the contemporary breeding-back experiments of the Aurochs, it remains to be seen whether it will make a hughe difference from an ecological perspective and if this can ever be scientifically proven.
I wrote nowhere that Koniks, Exmoor ponies or Przewalskis horses couldn not do the job and that "breeding-back" would be necessary for an ecologic replacement of the wild horse. Not at all. I just wanted to point out that it is not unlikely that many European wild horses at some point where of a black phenotype with an upright mane and that we could breed for exactly that phenotype and that such a strain of ponies could also be used for rewilding just like the Konik. Nothing more, nothing less.
DeleteAlso I have to correct you that we do not know about the ecologic difference between aurochs and wisent. We know that wisent inhabit higher latitudes while aurochs were more found in the lower latitudes, and also that aurochs inhabited more humid regions than the wisent. This is perfectly in like with what we know from cattle. Furthermore, cattle consume less wooden material than wisent do but more than horses do. This suggests niche partitioning and there is no reason to believe aurochs were different in this respect. Cattle work fine as aurochs subsitutes, also because there was probably little if any difference in ecology between aurochs and cattle.
True enough, you did not write so. But my point is more that by breeding back a new form is created while there are limited areas in which they can be of use. Why create a new one while there are replacements in store, so to say. Are we by doing so not just dading refugees in the lifeboat of the endangered wildlife?
ReplyDeleteAnd do we know enough about the ecological niches of Aurochs and Wisent? Cis van Vuure in his book on the Aurochs points out it is questionable whether the last refugees of both (Puszcza Jaktorowska and Belavezjskaja Poesjtsja) represent the prefered habitats of the concerned species. We don’t know how much Aurochs and Wisent cohabited the same areas or lived as neighbours in different ecological environments, though the assessment in your answer is indeed what should be expected. In my knowledge there are however no historical examples of areas in which both Wisent and cattle were present. Only recently there are the cohabitation of cattle and Wisent in Kraansvlak and since februari 2020 in the Slikken van de Heen. The results remain to be seen. Around 1999/2000 there was a discussion on the future of the Oostvaardersplassen, on expanding the territory and introducing the Wisent. As I understood it it was proposed by the Polish, which were invited to the discussions, that the Heck Cattle be removed and be replaced by only Wisent. This to prevent competition and interbreeding and because Wisent would be able to fill the niche of the Cattle. So, it being true that experiments and experience point to more woody consumption of Wisent, exact place in the ecological system is in discussion and in some way also a matter of choice.
To conclude I wish to remark that I only want to add to the discussion and don’t wish to offend. If I manage unwantingly to do so, I apologize. I regularly check your blogspot, and find it very informative and appreciate it very much.