The ecologic niche of the aurochs

The ecologic niche of the aurochs and where it differed from that of the wisent is hard to ascertain as the aurochs is extinct. Right? Not exactly. There actually a lot of things on the ecology of the aurochs and its interplay with other European herbivores that we can infer from various sources. 

The aurochs and other European herbivores of the Holocene

1. The aurochs was a grazer and probably much like cattle ecologically

 

The aurochs had the hypsodont denture of a grazer, like cattle today [1]. Anton Schneeberger writes that aurochs fed on acorns, mown grain and hay they were provided, and on branches of shrubs and trees during winter [2]. It has been reported that aurochs grazed in the same places as cattle and horses [2]. Since cattle descend from aurochs, and domestication probably did influence the basic diet in cattle [2], it can be assumed that aurochs and cattle were very much alike in food choice. There are differences within cattle, but that is mainly between highly derived breeds and landraces, since the former do not consume plants that are less digestible while the latter do [3]. 

Isotope analyses suggest that aurochs were found in more forested and wetter habitats than cattle, which mainly grazed on pastures [1]. It is of course possible that this is a difference between the wildtype and the domestic form, but it is more likely that the aurochs was pushed into these less accessible regions because open habitats were reserved as pastures for domestic cattle. Also, free-roaming cattle have been found to prefer wet habitats as well [5]. The continuous habitat loss was one of the driving factors for the aurochs’ extinction [2].  

 

2. The aurochs preferred lowlands and wetter habitat than the wisent 

 

The distribution of fossil and subfossil remains of aurochs and wisent have shown that aurochs preferred plain habitat and lowlands while wisent were found much more often in mountainous habitat [4]. This is also in line with what is known of the historic distribution of both species [2]. While it is true that both the wisent and the aurochs have been limited to hideaway regions due to habitat loss because of the human civilization and hunting, it probably has a reason why the hideaway regions of aurochs were marshes and lowlands and that of the wisent was mountainous habitat, and this region were the ecologic adaptions of the respective species. The wisent avoids areas which are too wet [4], which is why a replacement of the cattle at Oostvaardersplassen with wisent, as it has been discussed on occasion, is not feasible (Bunzel-Drüke, pers. comm.)

Nevertheless, both bovines must have met each other [2]. 

 

3. There was niche partitioning among Europe’s large herbivores 

 

According to the competitive exclusion principle in ecology, two or more species cannot exist in one and the same ecologic niche. Therefore, there must have been niche partitioning among Europe’s large herbivores and apparently this was the case. Cattle consume more wooden material than horses, which are strict grazers. However, cattle do not include as much wooden material in their diet as the wisent, which is a so-called semi-intermediate feeder. So there is a graduation on how much the respective herbivore relies on either grasses or wooden material, with horses relying the most on grasses and wisents consuming the most wooden material, and cattle being intermediate [4]. Since this niche partitioning is the result of evolutionary adaptions of these species, it is likely that this would also be the niche partitioning between wild horse, aurochs and wisent.  

Therefore, considering the differing habitat and food preferences, cattle and wisent would concur only to a limited extent in Europe’s nature systems. So the fear that wisent and cattle cannot be kept in the same reserve is baseless as long as the reserve provides habitats for both species. Another reason why some people have objections against (re)introducing cattle into European nature systems is that they are concerned that wisent and cattle would hybridize. However, a work by Frans Vera has concluded that cattle and wisent do not hybridize spontaneously and only under artificial conditions, which also often lead to the assault of the domestic individual by the wisent [6]. Furthermore, parturition does not occur in those hybrid pregnancies [6], what makes human assistance necessary. Thus, cattle and wisent would not produce hybrid populations in the wild even if mating between both species would occur. 

 

 

[1] Lynch et al.: Where the wild things are: aurochs and cattle in England. 2008. 

[2] van Vuure: Retracing the aurochs – history, morphology and ecology of an extinct wild ox. 2005

[3] Poettinger, J.: Vergleichende Studie zur Haltung und zum Verhalten des Wisents und des Heckrinds. 2011. 

[4] Bunzel-Drüke, Finck, Kämmer, Luick, Reisinger, Riecken, Riedl, Scharf & Zimball: „Wilde Weiden: Praxisleitfaden für Ganzjahresbeweidung in Naturschutz und Landschaftsentwicklung“. 2011

[5] Gander et al.: Habitat use of Scottish Highland cattle in a lakeshore wetland. 2003. 

[6] Vera: Do European bison and domestic cattle hybridize spontaneously? 2002. 

 

 

 

European wild horse colour phenotypes

Back in 2013, I did an illustration of the five colour phenotypes found in European wild horses according to genetic research and presented it in a post (back in the time when I called the European wild horse "tarpan", which I nowadays do not). I also put it on Wikipedia, but it was removed by some know-it-alls editing the German page. 

I recently did an updated version of that illustration. Back in 2013 I considered it likely that the European wild horse had a falling mane, which I no longer do (see here). I corrected it, and here is the result: 

It shows all the colour phenotypes confirmed for Equus ferus ferus so far, including: bay dun (top left), bay + nondun1 (top right), black dun (middle left), black + nondun1 (middle right), leopard spotted (bottom). For the references for the colour phenotypes see [1,2]. Black and black dun are caused by the allele a, which became the dominant allele later in the Holocene (whether the phenotype is black or black dun depends on the alleles on the Dun locus) [3], while Pleistocene horses all had the A+ allele, and thus were either bay or bay dun. A 2015 study [4] examined the alleles on the dun locus in a late Pleistocene (42.700 years old) wild horse from Russia and that of a 4000 years old horse (also from Russia). It turned out that the Pleistocene wild horse was heterozygous for dun and nondun1, thus had a dun phenotype. And since all wild horses from that time were A+//A+, it must have been bay dun and thus looked like the drawing at the top left. The 4000 years old horse (whether it was a wild horse or domestic horse was not tested), was homozygous for nondun1. Thus, if it was a wild horse, it looked like the illustration at the top right, since the a allele was not found in Russian samples. 

I also gave the leopard spotted wild horse a dark neck and face, matching the cave art (see here). 

Literature 

[1] Pruvost et al.: Genotypes of predomestic horses match phenotypes painted in paleolithic works of cave art. 2011

 [2] Ludwig et al.: Coat color variation at the beginning of horse domestication. 2009.

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

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

"Breeding-back" with horses?

When talking about "breeding-back", mostly the aurochs comes to mind. Currently, there is no "breeding-back" project for horses. However, reconstructing the life appearance of European wild horses could be worth a try. 

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. 

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.  

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. 

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. 

European wild horse mane: erect or falling?

The Holocene European wild horse is enigmatic. It seemingly was not common in the probably predominantly forested Europe of the Holocene [1] and it is not known when it actually died out, as the numerous accounts of free-ranging horse populations in Europe during the last two millennia might just as well describe feral horses, or hybrids. Consequently, its life appearance leaves room for speculation. For a take on this subject based on recent genetic data, see this post. 

The most puzzling question concerning the life appearance of the European wild horse is the mane. For a pretty long time, the falling mane of the domestic horse has been considered a result of domestication, as all extant wild equines have an erect mane. In domestic donkeys, domestication also resulted in a falling mane in some breeds (see here, for example). 

It has been claimed in recent years that European wild horses or the wild progenitors of the domestic horse might indeed have had a falling mane. The falling mane allegedly helps to divert rain from neck and face in a more humid environment, and indeed all extant wild equines are found in arid ecosystems. However, it has to be kept in mind that the horse was domesticated in the arid steppe, therefore this is not a compelling argument for the western wild horse having a falling mane. Another argument is that an Equus lambei carcass found in North America allegedly shows a falling mane (I have been unable to find quality photos of the carcass, unfortunately). It has to be kept in mind though that Equus lambei, the North American form, is probably more distantly related to the domestic horse than Przewalski's horses, or Siberian Pleistocene horses, which have/had short erect manes of about 15 cm length [2]. Therefore, the falling mane would have to have evolved at least two times in wild equines and such a mane cannot be inferred by phylogenetic bracketing for European/western wild horses. 

Then there are the manifold Pleistocene cave paintings which all show horses with an erect mane very clearly (see here and here, for example). Since many of the depicted horses show a strong resemblance to the Przewalski's horse, it has been assumed that the horses present in Europe during the late Pleistocene must have been of the przewalskii lineage. However, it has been found that a horse remain from Belgium from approximately 36.000 years ago is genetically closer to Iberian wild horses and domestic horses than to Przewalski's horses [3]. It is thus assumed that these short-maned horses are the ancestors of European wild horses (which the authors of Fages et al. call "tarpans") [3]. Interestingly, Siberian Pleistocene wild horses (referred to as Equus lenensis), which were short-maned to according to a carcass [2], are actually closer to domestic horses than Holocene Iberian wild horses. And the Przewalski's horse, which has an upright mane as well, is closer to the domestic horse than both the Holocene Iberian and Pleistocene Siberian wild horse according to Fages et al. [3]. 

Therefore, it seems highly likely that at least Holocene Iberian wild horses had an upright mane, and probably the (other) ancestors of domestic horses in the Eurasian steppe as well. 

Literature: 

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

[2] Lazarev, P.: Large mammals of the Anthropogene of Yakutia. 2005. 

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