Friday, 27 September 2013

Primitive Zebu cow from Sri Lanka

Like I wrote on this post, it is premature to think about which zebu breeds should be considered most reminiscent of their wild type, the Asian aurochs, and which should be used in a breeding-back project for this subspecies. I wrote that I think actually a lot of primitive zebu cattle yet unknown to us might be grazing around in southern Asia, waiting to be discovered and used in effigy breeding. 
A photo provided by Jochen Ackermann, who recently came across a zebu herd on Sri Lanka, confirmed this. It shows a zebu cow with a perfect wild colour and - most notably - almost no "zebu hump". 


Primitive Zebu cow on Sri Lanka, photographed by Jochen Ackermann
This cow is seemingly free of taurine influence, at least there is no indication for it. I don't know the name of the breed or if it even belongs to a specific breed. The other cows in the herd were coloured similar but more "usual" for zebus, with a prominent dilution on the ventral side of the body and/or also white spots. The bulls were elusive, but their hump was considerably larger. Indeed there seems to be a trend for the hump to be sexually dimorphic in more primitive zebus in Asia, judging from other photos I have seen. A herd of zebu-gray cattle hybrids at the zoo of Haag, Austria, also had bulls displaying a zebu hump but cows virtually lacking it. Perhaps the size of this appendage is related to the testosterone level. I still think it is a domestic feature and effigy breeding should try to reduce it as much as possible, and cows like that above certainly would be very helpful. But also her perfect wild type colour, the long legs and snout make me optimistic for effigy breeding with zebu. Unlike the case of the European aurochs, it might not be possible to reconstruct the phenotype of the Indian aurochs completely because zebus are more phenotypically derived, but achieving zebus with wild type colour, small humps, long legs and skulls and large, aurochs-like horns is absolutely possible, and all the rest could be done by mother nature later on. I hope that some suited Indian wildlife reserves will have such "wild zebus" one day. 



Exmoor vs. Konik - which one is the better wild horse substitute


Of course neither the Konik nor the Exmoor are surviving wild horses, it is zoological commonsense that the western subspecies Equus ferus ferus is extinct in its wild type. Both breeds proved to be hardy and suited to the climate of central and northern Europe. But which of these two breeds is a better substitute for the wild horse in phenotypic and behavioural respect? The Exmoor and the Konik are the centre of two rivalling ideologies, and advocates of the Exmoor usually reject the Konik and vice versa. But the breeds do not rule out each other, and I want to take an objective look at this issue here.

Which one is a direct European wild horse descendant?

According to the current knowledge, none of them. All of the modern domestic horses apparently descend from one single domestication event in the Eurasian steppe, but they seemingly experienced female introgression on the continent. See here. This is true of any modern European domestic horse, and so also of the ancestors of the Konik and Exmoor.
The Konik is neither a hybrid population of the last Polish wild horses, as it is widely stated, nor is it a breeding-back attempt with such as a base. It is in fact a landrace descending from rural Polish ponies of mixed origin. According to Wikipedia, pre-domestic wild horses were present on Great Britain until at least 5500 years ago, so that domestic and wild horses might have met each other on Great Britain, there is still no evidence that the Exmoor directly descended from the last remaining wild horses because it shares the same limited Y chromosome diversity with many other domestic horses from around the world (see the previous entry). One could argue that domestic introgression and bottlenecks could have produced this result, but only through systematic culling of wild stallions and replacement with domestic ones in the moor, for what there is no evidence and what also would have greatly altered the population.
Although both the Exmoor and the Konik are no remnant population of the European wild horse, nothing rules out that they are themselves very original and do resemble the wild horses in several respects.

Which one has the more authentic phenotype?

To remind you, the European wild horses did not have a uniform but variable appearance, at least concerning their colour. I was basing myself on genetic and and historic evidence when I did this wild horse reconstruction:



As you see above, genetic and historic evidence suggests that 5 colour variants were present among the European wild horse: bay (like the Exmoor), bay dun (f.e. Przewalski), black (some single Koniks but also other “celtic ponies”), black dun (Konik). Dun is a dilution gene that makes the leg stripes and eel stripe more prominent and creates somatolysis in the open field. And indeed Koniks (and other dun horses) are perfectly camouflaged in such habitats. The lack of dun produces darker colours which are suited to more closed habitats, so it happens that Exmoors are wonderfully camouflaged in forested habitats. That is not to say that the Exmoor is a “forest type” pony and the Konik an “open field type” pony, because some Koniks also show darker expressions of their black dun colour which suit a forested habitat. Historic evidence suggests that the majority of Europe’s wild horses was dun coloured, but this gene has yet to be tested for the bone remains of the Holocene remains to be sure. Nevertheless, both the Exmoor and the Konik display one of five possible colour morphs within a wild population, respectively.
Because of their mixed origin, some Koniks still carry genes for a sorrel colour or white spots. White spots are also present in some Exmoor ponies, but rarer than in the Konik and breeders select against it.
Both the Exmoor and the Konik have a small, sturdy body with a robust head and a short mane, but there are also many Konik lineages with a more gracile built and long manes, resembling usual riding horses. The “beard” which is present in the Przewalski’s horse and also described for the European wild horses is prominent in the Exmoor, not so much in the Konik.

Which one has the more natural behaviour?

Because the domestication of the horse strongly focused on behavioural traits, no domestic horse has a truly “wild” behaviour; this is even evident under natural conditions. Wild horse behaviour, based on that of the Przewalski and what is described for the historic wild horses, includes shyness in the open field but aggressive behaviour against domestic horses and man in captivity, and defending themselves harshly against predators.
Koniks remain relatively tame under natural conditions, while Exmoors tend to be shyer because of their feral history. Koniks are reported to behave dominant over other horse breeds even if those are larger [1]. I don’t know about the dominance of Exmoors over other horse breeds.

Which one knows how to deal with predators?

We don’t know how much the rural ponies ancestral to the Konik had to deal with predators, but since they were husbanded, it is likely that they were largely protected. When Koniks were released in the Spanish Atapuerca mountains last year, five of them were killed from wolves.
Exmoors have been living feral in southern England for at least one millennium, and wolves did not disappear from the island before the 16th century, what suggests that they know how to deal with predators. They are also known to form a defensive circle around their foals, a common behaviour among ungulates. It was even reported that an Exmoor defended itself successfully in a puma attack in the moor [2].

How about the resistance against diseases?

Both the Exmoor and the Konik have one disease they are prone to, respectively. In the case of the Exmoor, it is a kind of horse mange (“Sommerräude” is the precise German term, I don’t know the English one). Some Koniks are prone to laminitis, especially when raised in a barn [1]. But all in all, both breeds are resistant against most other horse diseases.

Conclusion

The behaviour of the Konik seems to be more domestic than that of the Exmoor and they are less used to predators, but I hope that these traits will redevelop if a large enough population is released in a nature area. When the right Koniks are chosen (with a sturdy body and short mane), both Exmoor and Konik represent one of five phenotypes that likely appeared within the European wild horse, although the Konik is slightly more gracile and long-maned than the Exmoor. Doing tests for the dun gene in Holocene wild horse remains could reveal if there was a regional difference in the occurrence of dun and non-dun wild horses, and if there were non-dun wild horses at all. Genetic testing could also prevent getting animals with genes for white spots or sorrel colours into wilderness areas. Releasing Koniks and Exmoors side by side in one reserve would be no mistake in my opinion, because the breeds compensate each other: Koniks lack the bay gene but have black and dun, Exmoors have the bay gene but lack black and dun. Since the other phenotypic respects are about equally primitive if the right individuals are chosen and their ecologic capacities are about the same, and they would even compensate each other regarding the resistance against diseases, mixing them for rewilding purposes would only have positive effects (but I am suggesting to mix both breeds in general, not at all, both are unique breeds).  The majority of the animals within a Exmoor x Konik population would most likely be coloured bay dun, because bay is dominant over black and dun is dominant over non-dun – and historic and genetic evidence suggests in my opinion that bay dun wild horses were the most common within the populations.

A little game - recognizing Exmoors and Koniks only by drawings of their contours to see how different their phenotype beside the colour really is - will come soon. 

Literature

[1] Tadeusz Jezierski, Zbigniew Jaworski: Das Polnische Konik. 2008.
[2] Baker, Sue, 2008: Exmoor Ponies: Survival of the Fittest – A natural history.

Sunday, 22 September 2013

Visiting Chillingham cattle - was there a white Aurochs?


In September last year, I visited the Chillingham Park in Northumberland, England, to have a look at the main herd of Chillingham cattle. These cattle are a very rare and ancient cattle breed, remarkable for their feral history, genetic isolation for at least 300 years and a high degree of inbreeding. I talked to Richard Marsh, the Chillingham cattle warden, and he told me a lot of interesting facts about this herd that I am going to share here. It is often claimed that they are totally wild, undomesticated cattle, but how wild are they truly? Are they related to the aurochs in some way? Let’s dive a little deeper into the history and biology of that breed.


The aurochs died out in Great Britain 3500 years BP [1], before domestic cattle arrived. Claims that Chillingham cattle descended from the first cattle brought to England by the Celts or later the Romans are neither supported by historic [1] nor molecular data. Chillingham cattle belong to the T3 haplotype [2], which is characterized as the “typical modern European haplotype” by Beja-Pereira et al. 2006 [3]. Chillingham cattle is sometimes connected with the aurochs because Charles R. Darwin recognized similarities between the aurochs’ skull and that of Chillingham cattle, but this breed isn’t any more aurochs-like than primitive cattle landraces from Iberia, Italy, North Africa or the Near east.

Chillingham skulls with more or less aurochs-like skulls
From the first half of the 13th century, British baronial hunting parks included also cattle for hunting [1]. These cattle also served as ornament, and the European nobility usually preferred white animals for such a purpose (f.e. see the Austrian white donkey). While many of the hunting park herds became strongly influenced by Highland and Longhorn cattle, resulting in the modern White English Park cattle [1], Chillingham was the only location to retain pure herds of these hunted cattle, which were probably founded by collecting medieval husbanded cattle between the 13th and 17th century [1].  In the 13th century, a wall around the Chillingham park was built and the cattle were now protected from Scottish poachers, and they survived in this enclosure until today. The cattle live in a feral state and were hunted by the nobility just like Britain’s feral ponies. When they were hunted in earlier days, they were known to be very aggressive and killed dogs, horses and humans involved in the hunt.

Historic engraving by Thomas Bewick, showing the hunt of a bull at Chillingham
Chillingham cattle are, like most cattle back in the medieval times were, quite small, standing only 110 cm at the withers and weighting 300 kg (for bulls, cows are slightly smaller). However, we know through bone remains that there was a slight trend to size reduction in the population over the last centuries. Their body shape is, although comparably slender and firm, domestic in having no shoulder hump and a rear that is as heavy as the forehand. The udders of the cows are surprisingly large. Chillingham cattle have large heads (sometimes also with a long skull), but their body is comparably short-legged and longish. The horns are mostly upright (100° and more) but aurochs-like in curving inwards, with slightly upwards-inwards facing tips. Among the skulls on display, I found some specimen having even more aurochs-like horns than those in the current population have. Perhaps they stem from the times prior to the most dramatic bottleneck event in the 1940s. The colour of Chillingham cattle is interesting: the nasal mucosa are black and cows are coloured creamish (i.e. darker) on the neck area, what usually is indicative of the wild colour allele E+ (but the calves are completely white while wild-coloured calves are always born reddish). Even more surprising is that bulls are slightly darker (grayish) than the cows, what suggests that they retained some kind of colour dimorphism. Additionally, they have those numerous small black spots on the face, neck and shoulder area. I have no clue about the genetic background of the coat colour in Chillingham cattle. UPDATE: I found out that the colour of Chillingham cattle is caused by the colour-sided allele (Cs) on a base colour that is either black or wild type-coloured. No other breed in the world has the same colour except White Park cattle. The hair on the neck and face area is very dense and curly in Chillingham cattle. This “mane” is claimed to serve as a protection of the bull’s skin during a fight. Some Spanish cattle like the Fighting bull or Sayaguesa sometimes also show is feature, and it is apparent in single Oostvaardersplassen bulls as well. Therefore I wonder if aurochs also may have had it to a certain extent, but this is only speculation.  


Chillingham cattle are dedomesticated in the sense that they are free to breed themselve and the dominant bulls that cover the cows, and there has never been medical care or any other form of custody. Nowadays the cattle are supplementary fed during winter because the area they live on is too small to provide food for the whole herd, under natural conditions they would migrate. Predators are not present in the Chillingham Park and I don’t know if they ever were, since it was a guarded game park of the nobility. The numbers of Chillingham cattle probably were regulated by food availability, diseases and hunting. Artificial selection on Chillingham cattle was not totally absent. For example, individuals with black ears and light noses were selected out. Also, selection probably played a role in surviving the genetic bottleneck [1] (see below).
When Chillingham cattle, in spite of being feral for several centuries, still have a more or less domestic body, upright horns and small size, why is there a trend in Oostvaardersplassen for Heck cattle developing “wild” body shape and proportions and aurochs-like horns? I think the key to this question is that the Oostvaardersplassen cattle descend from a very variable founding population. Evolution works faster in a variable population than it does in a homogeneous population. And perhaps the selective pressure for saving energy never was that strong at Chillingham because of the supplementary feeding (I don’t know when they started to feed them). Regarding the horns, we should not forget that they are some kind of aurochs-like in Chillingham cattle. They curve inwards, what is functionally very advantageous in intraspecific competitions and was the case in every single aurochs specimen we know. It is possible that the horns of Chillingham cattle were more aurochs-like prior to the bottleneck event, based on the skulls which I saw.

The numbers of Chillingham cattle were documented from 1689 onwards, showing a peak number of 82 in 1913 before they started to decline [1]. The population crashed in the severe winter of 1947 to 13 individuals. Not only have they gone through this genetic bottleneck, but also 300 years of inbreeding, resulting in a highly uniform nuclear genome [2]. Based on mitochondrial DNA, the whole modern population descended from a single recent female founder [2]. It is theorized that Chillingham cattle avoided an inbreeding depression due to purging out deleterious alleles, which was executed by the wardens during the 19th century: weak bulls were castrated and weak cows shot for beef before they could reproduce [1]. Natural selection probably played a role as well, and nowadays there is no culling or castration anymore. Furthermore, cows allegedly kill their weak calves.

I was told that the sex ratio within the herd is 1:1. Having several adult bulls of any cattle breed on one restricted area can lead to trouble, and indeed Chillingham bulls often have severe fights, sometimes injure or even kill each other. The bulls are in constant alertness and have a considerably shorter life span than the cows (13 years). The often repeated concept of a “king bull” ruling the herd is probably too simplistic [1]. Chillingham bulls, like bulls of any other cattle breeds, live in groups of two or three, but are not territorial [1]. Adult bulls vocalize much, something that I also experienced when I visited the herd. It is remarkable that there is no rut and they mate all the year round – this has disadvantages for cow and calf during winter and usually free-roaming cattle redevelop a natural reproduction cycle. Perhaps this was not the case in this feral population because of the supplementary feeding in the cold season.
I was told that the cattle go into the deciduous forest for resting, but interestingly never go into the conifer forests.


In 2009, there were 85 individuals at the Chillingham Park, additionally to a reserve herd in the north-east of Scotland. I hope that in the future there are more breeding locations in order to conserve these remarkable cattle. It is uncertain whether they can resist diseases transferred from other cattle breeds because of their genetic uniformity, but only trying it will show.


The coat colour of Chillingham cattle as described above is also interesting when looking at some of the cave paintings in the Lascaux cave. Among aurochs depicted in the usual colour (red cows, black bulls), there are some individuals that are drawn only in contours, with prominent black spots on the face, neck and shoulder area. Could these represent Pleistocene aurochs having the coat colour of Chillingham cattle? 
"Spotted" aurochs bull at Lascaux
This is not totally implausible, as a 2011 study revealed that cave paintings showing white spotted horses were indeed authentic [4]. There are not any other artistic depictions than the Lascaux paintings showing such a colour, nor are there any written references of it. This colour variant, if it existed in wild aurochs, must have persisted at least until the domestication of taurine cattle 8.500 years BP. I do not consider it likely that there were aurochs displaying that coat colour, as the evidence for it is very weak. But it could be worth to investigate by identifying the genes responsible for the Chillingham colour and trying to find it in Pleistocene and Holocene aurochs remains, just like Pruvost et al. did in the case of the wild horse. UPDATE: The colour of Chillingham cattle is caused by the homozygous presence of the Cs allele on a usual base colour. If the colour-sided allele is present only heterozygous, this is the outcome with wild colour as basic colour. I don't consider piebald aurochs to be very likely, as most if not all wild animals are solid-coloured. 
That’s a version of my reconstruction of the Braunschweig aurochs painted in Chillingham colour:



Literature:

[1] Stephen J. G. Hall: The white herd of Chillingham. Journal of the Royal Agricultural Society of England. 1989.
[2] Gavin Hudson et al.: Unique mitochondrial DNA in highly inbred feral cattle. 2012.
[3] Albano Beja-Pereira et al.: The origin of European cattle: Evidence from modern and ancient DNA. 2006.
[4] Melanie Pruvost et al.: Genotypes of predomestic horses match phenotypes painted in Paleolithic works of cave art. 2011.

Thursday, 19 September 2013

News from the Quagga Project 2013


According to their report of August 2013, the Quagga Project has 89 animals on 10 locations. Two foals have been born this year, which seemingly are of good quality:

One of the foals born in 2013 (photo by Quagga Project)
Another foal born in 2013 (photo by Quagga Project)
In their report they also show a genealogical tree of one of their F4 individuals called Mary, which has almost completely stripeless legs. According to the project, HN12 (F4 individual) is the most Quagga-like animal they have so far. As far as I can see, most Rau zebras born between 2010 and now are about as good as these two individuals. Zebras mature later than domestic horses (mares at about the age of 2, stallions 4 years), so we’ll have to wait a bit until we see the offspring of the animals linked down below. I’m really looking forward to see the Rau zebras of 2020!

HN12 (photo by Quagga Project)
"Mary", another F4 Rau zebra (photo by Quagga Project)
I’ll do some Quagga artwork soon, meanwhile here are photos of the Quagga specimen that I took at the Senkenberg museum, Germany (I have one from Berlin too, but that one is too dark):




Tuesday, 17 September 2013

Heck cattle at Oostvaardersplassen - A special population


In 1983, 32 Heck cattle were released in the Dutch reserve Oostvaardersplassen, an area of 5600 hectares. Oostvaardersplassen is the only place where Heck cattle live under natural conditions without much influence of man, such as no supplementary food during the first decades and no artificial selection. The cattle grew to 350 individuals in 2011 and evolved into a very heterogeneous population, making it a very interesting dedomestication experiment. It is cool to see some individuals with broken horn tips, split ears or even scars; that shows that they have a rough life and those which do best pass on their genes.
Keep in mind though that Heck cattle in Oostvaardersplassen are by far not the only free-ranging cattle population in Europe. Chillingham cattle and Betizu cattle have been living freely since centuries, and especially the last one is way more dedomesticated than the Oostvaardersplassen cattle. Sadly though, feral cattle (or feral domestic animals in general) are an ashamedly understudied field. Their social behaviour, reproduction cycle, habitat choice, food selection, species interaction and so on could tell us so much about their ancestral wild type, the aurochs. And if it is a very variable population (what makes the Oostvaardersplassen cattle so interesting here), a statistic evaluation of the changing frequency of certain phenotypic features over the time would provide a lucid example of evolution at work

Most of the Heck cattle at Oostvaardersplassen do barely resemble the aurochs. When people in the Netherlands started to buy Heck cattle from other countries in the 1980s, the breeders mostly sold their less good cattle (this is understandable, I would have done the same), and some individuals were bought as calves, so that their quality was not yet discernable. Therefore, most Dutch Heck herds, and the Oostvaardersplassen herd in particular because no artificial selection takes place, are less aurochs-like than many German herds, but there are also some good animals among them (more on other Dutch herds in a future post).

Nevertheless, the population at Oostvaardersplassen is very valuable because it has been exposed to intense natural selection over the past 30 years. Predators are still absent in the reserve, so the selective pressure mainly concerns the ability to survive harsh winters, resistance against injuries and competition for food, social dominance and breeding rights. I am not aware of any diseases in this population.
The ability to survive harsh winters and to live on poor forage is dependent on saving as much energy as possible. This requires a thick and insulating winter coat (Heck cattle, like other cold-resistant cattle breeds, have such a winter coat), but also a small, hairy udder, short dewlap and short scrotum in order to reduce the heath loss. Those individuals which loose too much energy during winter cannot keep up sufficient strength or fall ill and die, what favours the cattle that are more effective in saving energy and resist diseases. Storing fat during autumn is another factor that is important for cattle to survive strong winters. Also, seasonal adaption of the reproduction cycle is important for the cow and calf’s survival, because cows having calves during the cold season have difficulties in subsisting themselves and their offspring. Therefore, cattle should mate during August/September and give birth during spring, like it seemingly was the case in the aurochs [3], and is the case in Highland cattle under natural conditions [3][2]. Heck cattle usually give birth all the year round like most domestic cattle, unfortunately there is no information on the reproductive cycle of the Oostvaardersplassen population that I am aware of.
The competition for social dominance (which has advantages such as better feeding places and less stress) and breeding rights is directly connected to the animal’s superiority in intraspecific fights, which is dependent on the weight/size, horns and also the psyche of the individual [1][2]. Long-legged and agile animals also have a higher chance in succeeding in a fight. Intraspecific fights occur in both sexes, but especially the mating competition of bulls has a direct influence on the evolution within the population. High shoulder spines that allow large neck and shoulder muscles to develop provide another important advantage in combat; that’s the kind of “hump” that’s present in all wild bovines, aurochs included. Also the horns of the aurochs were shaped for a purpose: their curvature had a functional advantage in competitions, because large, forwards and inwards-facing horns made it possible for the animal to pull and push the opponent more effectively than other horn shapes would do. This is the reason why bovine species fighting in a similar manner also have very similar horns (Kouprey, Yak) and why the aurochs’ horns were relatively uniform, no matter which respective time and region.

© treverius on flickr
Having tried to make predictions on how the functional phenotype (among other aspects) of a released cattle population might change under such conditions, now lets have a look at how the present Oostvaardersplassen Heck cattle look like.
The body shape of many cows is still domestic in having a bulky rear, visible pelvic bones and no hump (thus, comparable to usual Heck cattle). However, single cows seem to develop a slight hump and a slender waist. This trend is even more apparent in bulls, some of which do really have an athletic body shape with a clear hump and a slender waist, resembling Spanish fighting bulls and wild bovines. Also, many bulls and cows have long legs as in the aurochs. Therefore, the prediction that body shape and proportions in a feral variable cattle population re-develops to an athletic, aurochs-like body seems to be confirmed, because such a body conformation is found in no other Heck cattle population. Down below you see screenshots of an Oostvaardersplassen bull (sadly with the wrong colour and horns) that has perfectly aurochs-like body shape and proportions. However, there are still some quite bulky and dachshund-proportioned Hecks in this reserve.

Slender, long-legged bulls
Perfectly "wild" proportions and body shape (Screenshot from youtube)
The horns within this population are mostly steppe cattle-like and thin, the length is varying and they are oriented very upright both in bulls and cows. However, I was surprised to discover cows with horns facing more forwards and inwards than in any other Heck cows. This is a strong hint that this horn shape developed in Oostvaardersplassen and therefore is a product of natural selection instead of artificial selection. In essence, the curvature of the horns in these two individuals is nearly perfect, except that they are oriented to vertical. I see the same tendency several in other cows and also bulls in Oostvaardersplassen.

(© evoergo on flickr)
(© Frits van Hout) Cows with aurochs-like inwards-facing horns, 
very likely a product of natural selection
The skull of the Oostvaardersplassen Heck cattle is short and paedomorphic like in most other representatives of the breed. However, surprisingly some cows show an elongated skull, similar to Sayaguesa. I wonder what causes this development and if a longer snout perhaps provides an advantage for grazing, or if it is influenced by environmental factors.
The colour of those cattle is extremely variable. Dark brown bulls with a kind of saddle and either dark or reddish-beige cows are most common, but black cows and black bulls, as much as reddish brown or beige bulls do appear. Gray individuals exist in both sexes and are a relatively common sight. The portion of spotted animals seems to be higher than in usual Heck herds, unfortunately. These spots either are limited to the forehead or cover the whole body.
Spotted bull calf (©Jaap Rouwenhorst)
There is no size data for the Heck cattle at Oostvaardersplassen, and also no useful photos from which the size of the animals could be extracted, so we can only speculate how large they are. Do the conditions in the reserve favour a size increase or decrease against the 140 cm shoulder height in bulls and 130 cm in cows? As discussed above, the natural selection created by the physical competition of the animals likely favours larger animals. But considering the small size of the reserve, the high density of herbivores and the limited amount of food, as much as the absence of predators, makes Oostvaardersplassen a kind of island. These island conditions favour a size decrease in larger animals, as numerous examples of insular tetrapod evolution have shown. After all, the aurochs itself “dwarfed” slightly on Sicily after it became isolated from the mainland. It makes sense that a smaller animal needs less energy than a larger one, and a healthy and strong small bull might succeed over a larger but emaciated one in a competition. Therefore, we have to assume that the Heck cattle at Oostvaardersplassen are as large/small as the average of the breed given above, or even slightly smaller.

If the conditions like they are now remain unchanged, how will the population in Oostvaardersplassen develop in future decades? I think that on a middle- and long-term sight, the portion of animals with an athletic body and aurochs-like proportions and horns will increase, while the bulky and domestic looking ones will get constantly fewer because these factors have a considerable impact on the fitness of the animals. Also, if the food situation does not change (f.e. by increasing the supplementary food that already is provided during winter), those with the smalles udders and shortest dewlaps and scrota, and most effective winter coat and resistance to diseases will become more common.  The island situation of the reserve will favour a size decrease more than a size increase. The colour of the animals has, as far as we know and in the absence of predators, no direct influence on the fitness of the cattle, so it will remain heterogeneous for a very, very long time. Perhaps sexual selection favours dark bulls and lightly coloured cows, but only on a very long term.
In essence, future Heck cattle in Oostvaardersplassen will be more adapted to their habitat and living as a wild animal than they are now. They probably will evolve into a population with aurochs-like horns and proportions/body shape, but varying colours and a small size. Probably it would also take a considerable time span until these alleles are fixed, and I am speaking perhaps of centuries. But what if man would “help” natural selection to speed up the process? Individuals with undesired features, such as grayish coat colour and steppe cattle-like horns, or many of the spotted individuals, could be culled, and a wild type colour with the right sexual dimorphism could be fixated. To compensate the loss of individuals, cows of herds that add what is lacking in the population can be added, such as from the Wörth herd (for the horn dimensions and curvature) and the Taurus cattle at Lippeaue (for the size, proportions/body shape and horn curvature). Later culling should focus on the bulls in order not to decrease the population too much, and because single bulls have a greater influence on the evolution within the population than single cows.
This plan could lead to a dedomesticated, wild cattle population that is adapted to their habitat and resembles the aurochs very well. However, it is up to the responsible people if this is turning into reality or not.

It seems that the next step in Oostvaardersplassen will be expanding the reserve. The plan of Oostvaardersland, a new 150 square kilometres large nature area that would be formed by the connection of Oostvaardersplassen to the reserve Hosterwold by a corridor named Oostvaarderswold, ran into political trouble. This is a shame, as Oostvaardersland would be one of the most precious nature areas in western Europe. Not only because of its rich avifauna and the wet zones which are very important for the amphibian fauna, but also because it is the only place in western Europe where large populations of cattle, deer and horses live side by side. Also, the cattle would have the chance to chose between forests and open grassland, what would tell us more about the habitat preference of this species. However, let’s stay tuned and see if Oostvaardersland is going to happen.


Literature

[1] Frisch, Walter: Der Auerochs – das europäische Rind. 2010.
[2] Julia Poettinger: Vergleichende Studie zur Haltung und zum Verhalten des Wisents und des Heckrinds. 2011.
[3] van Vuure, Cis: Retracing the Aurochs - History, Morphology and Ecology of an extinct wild Ox.

Saturday, 14 September 2013

Over-purity as a danger for the Wisent?


Ok, this is a little bit off-topic, but it is bovine-related and certainly a very important issue that I don’t want to miss here.

It is well-known that the Wisent went through a dramatic bottleneck in the 1920s; only 54 individuals remained, and these descend from only 12 ancestors [1]. The contribution of these ancestral individuals to the modern population is uneven and dominated by one pair in particular, so that the modern gene pool is even smaller [1].

The small genetic diversity and the high degree of inbreeding is regarded as one of the main dangers to the global wisent population. Inbreeding affects the skeletal growth, leads to skull asymmetry, deformation of the male gonads, increases the rate of stillbirths, decreases female fertility and the resistance against diseases and parasites [1]. Wisents are vulnerable to diseases such as posthitis and balanoposthitis, foot-and-mouth disease, cattle tuberculosis, bluetongue disease and others. Epidemics are an acute danger to wisent populations, even in captivity. In the Bialowieza Primeval Forest, about 20% of the mortalities are caused by diseases [1].

The modern Wisent population is separated into two genetic lines. One is of pure bonasus individuals, and the other one has introgression of one single caucasicus bull. Curiously, the inbreeding effects are more severe in the LC-line. In the Lowland line the inbreeding coefficient is equal to 44%, in the Lowland-Caucasian line 26% [1].

"Kaukasus", the last pure Caucasian wisent
Line breeding separates the very small gene pool into two even smaller sub-pools and is something that usually would be avoided in the conservation of a species that is highly inbreed and homozygoteous. The reason behind this is to preserve the pure members of the lowland line, although the introgression of only one bull of a different subspecies eighty years ago probably would have little effect on the global wisent population, except that the genetic diversity would increase (what is, in fact, necessary to preserve the species). While the L line is a closed pool, the LC line is “open” and therefore pure lowland bison are constantly mixed in. This leads to a further decrease of genetic diversity, because the Caucasian influence gets increasingly diminished [1]. Therefore, line breeding increases the problem of inbreeding and homozygosity.
Therefore, one way to prevent the further loss of genetic diversity that I propose is to stop the line breeding by “opening” the L line, so that the two very small gene pools could fuse into a larger one and to prevent that the Caucasian influence disappears altogether. The affect of this influence of only one bull on “pure” Lowland wisents would probably be very small, as both bonasus and caucasicus belong to the same species and show only slight phenotypic and ecologic differences. It confuses me that there are efforts to separate subspecies and subspecies hybrids (with hardly any recognizable difference except inbreeding-related issues) in an endangered species with a critically small gene pool like the Wisent, while there is no such action in a genetically diverse, healthy and not endangered species like the American Bison, of which the two subspecies also intermixed in some populations (f.e. Wood Buffalo National Park) or not even to purge out the influence of domestic cattle in the American bison.

Another but certainly controversial step to increase the genetic diversity of the wisent is to cross-in single American bison and mate the results with pure Wisents again until the American influence isn’t recognizable anymore. In German there is the nice term “Verdrängungszucht” for this kind of breeding, what could be translated with “expulsion breeding” or so. The mere existence of such hybrids, or individuals with “unproven pedigree” are regarded as a threat for the Wisent in the action plan for the conservation of this species by the Polish Academy of Science [1], although it certainly would compensate the larger, immediate danger of the small genetic pool. It is true that uncontrolled and nontransparent hybridization, f.e. in a feral population, is an indirect danger for the Wisent as a species, but controlled introgression of the closely related American species might be helpful in overcoming the severe inbreeding depression of the European bison.
In the early 20th century, hybrids of wisent and Am. Bison, but also domestic cattle hybrids, were not rare at zoos and were in fact a threat for the conservation of the species, because there was the danger that hybrids and pure wisents become all mixed up and indistinguishable. That’s why a pedigree book for the Wisent was set up in 1931 – the first pedigree book for any endangered species – to ensure that the Wisent will survive in its original form, un-altered by uncontrolled hybridization [2]. Therefore, it is understandable why hybridization per se is still regarded as a threat to the Wisent, but today it is also apparent that the high degree of inbreeding and the resulting low resistance to diseases and parasites and other negative consequences are a drastic and immediate danger for the global population. Controlled introgression by few hybridization events would be one way to add genetic diversity to the wisent gene pool, but what other effects would controlled hybridization and back-crossing have on the Wisent?

The European bison and the American bison are closely related and can interbreed without any fertility problems. Because of this, several authors treated them as one species in the past. Phenotypic differences are apparent; the American bison has a more longish and massive body, more opulent fur on the head forelegs and also the horns are not as long but thicker as in the Wisent, among other differences. However, both species are ecologically similar, except that grasses make up a higher portion in the diet of the American bison. The Wood bison, B. b. athabascae, inhabits a similar habitat as the Wisent did in ancient Europe. In 1940, hybrids of American and European bison were released in the Caucasus. After controlled culling and subsequent replacement with pure wisents, the portion of American blood within the Caucasus population is now estimated being only about 5%, although the American influence is still slightly visible in the phenotype of the animals. Allegedly this population has a destructive influence on the local flora because of the hybrid origin. I am not familiar with the facts behind this claim, but I am sceptic about it because according to the food choice of the A. bison, the only difference to be expected is that they eat a higher amount of grasses than pure wisents would do – and originally there were two other species of grazers in the Caucasus that relied on grasses to a large extent (aurochs and wild horse). But of course does the presence of herbivores change the frequency of certain plant species, because herbivores decimate some species more than others. This is to be expected in every ecosystem, and this observed change in the plant community might be interpreted as a “damage” if someone expects the animal to cause damage. It is further claimed that the population released in the Caucasus is less tolerant to cold and less adapted to mountainous habitat because of the influence of the American bison. But the lacking adaption to the mountainous habitat probably isn’t due to the American influence in particular, but the Caucasian Wisent very likely had special adaptions to its habitat that are not present in the Lowland Wisents as well. For example, it was smaller, had shorter higher hooves and a less shaggy coat [3]. The claim that the American influence made them less resistant to cold is very likely incorrect, since American Bison resist temperatures down to - 40° Celsius.

Wisents with American bison introgression in the Caucasus (Photo by Sergej Trepet) 
In order to conserve the Wisent as a species but to increase the genetic diversity by controlled hybridization, not a patchwork of American and European features should be the objective, but a homogenous Wisent population with slight American introgression that is not visible. This is possible, as we know from the fact that many modern American bison populations experienced introgression from domestic cattle in the past, but the cattle apparently left hardly a trace in the phenotype, behaviour or ecology of the bison (however, this isn’t the case for all herds). Controlled hybridization followed by “expulsion breeding” by constant back-crossing with pure wisents can result in a wisent population that looks like the wisent, behaves like the wisent and has the ecology of the wisent, but is more genetically diverse than the highly inbreed “pure” populations. Individuals that show clear traces of the American bison can be selected out. When American bulls are used and only their female offspring is chosen for further breeding, the entrance of “foreign” Y chromosomes is effectively prevented (vice versa for the mitochondrial DNA in cows).
What would be the effect on the genetic structure of the Wisent? As a population geneticist would say, its allele frequency would slightly change. But as we know through modern genetics, populations always change (genetic drift). The modern wisent is necessarily genetically different from the Wisent of the 19th century before the bottleneck event. And the Wisent of the 19th century was genetically different from that of the Bronze Age et cetera.

Surely, uncontrolled and nontransparent hybridization of wisent with American bison or even cattle, be it in the wild or captivity, is a threat for the conservation of the species. But a controlled and transparent breeding plan like described above might be seen as a chance for the Wisent to gain more genetic diversity to overcome the menacing effects of inbreeding in the species. Perhaps the European bison Pedigree book one time will allow a third genetic line with American introgression besides the Lowland line and the Lowland-Caucasian line, where every interspecies mating is transparent and recognizable. In this case it would always be possible to distinguish between wisents with introgression and those without, and the amount of introgression is always transparent as well. If the Pedigree book is against such a step, there is still the possibility to set up a new breeding book for that lineage. Surely this would be controversial and also cause disaffirmation, but if it turns out that Wisents with slight American introgression are healthier and more resistant to diseases than their “pure” counterparts and show no apparent signs of hybridization (neither in their phenotype, behaviour or ecology), maybe there will be shift in looking at this strategy to safe the wisent, for which, as the conservation plan states, “the danger of extinction still remains”. Maybe it will also cause a different look at the 700 wisents that are not registered in the Pedigree book and also the population in the Caucasus. The latter population has been living in the wild for more than 70 years now and grew to magnificently large numbers (though poaching is a serious problem), and therefore is certainly precious. Culling of bulls and replacing them with pure Wisents could further reduce the phenotypic effect of the American bison introgression.

In my opinion, studies comparing the food choice of American bison, European bison and hybrids should be set up. Also it is necessary to investigate the resistance of the hybrids against diseases and other negative effects of inbreeding (the existing population in the Caucasus could serve as a model) and to investigate which of the two subspecies of the American bison is better-suited for such an attempt. This could be a scientific basis for a breeding experiment executing controlled and transparent introgression into the Wisent pool as described above without affecting it as a species in order to overcome the most serious and immediate threat for the conservation of the species.

Here's a video of the wisents in the Caucasus with bison introgression: 




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
  • [2] Jan Raczynski, Malgorzata Bolbot (2009): The European Bison Pedigree Book.
  • [3] Ninell Melkadze, Nargiza Ninua, Izabella Skhirtladze (2009): Catalogue of the type specimens of Caucasian large mammalian fauna in the collection of the National Museum of Georgia


Saturday, 7 September 2013

Maronesa - a relict breed from Portugal


By “relict” I of course do not mean this breed is a surviving aurochs population. But Maronesa is one of the very few remaining cattle breeds that resemble the aurochs overall to a large extent in overall appearance, apart from their size.

Maronesa was and is used as a draft breed and their range is centred around the North of Portugal. This breed usually is raised in the upland regions and live freely most the time of the year. They are used to heavy raining and snowfall, and even are known to fight of wolves and defending their calves.
Some genetic studies find it to be well-differentiated among Iberian breeds [1], but they also show striking phenotypic similarities to Auroquesa, Barrosa/Cachena and some other Northern Portuguese cattle breeds. These similarities concern f.e. horn shape, face shape and overall appearance, but Maronesa has a much more Aurochs-like coat than the other breeds.

Well-marked sexual dimorphism
In fact, Maronesa is one of the very few breeds that still exhibit a nearly correct aurochs coat colour: the bulls are dark brown to black with a lightly coloured eel stripe, the cows are reddish brown and darker on neck, head, tail and anterior side of the legs. Both sexes show a clear mealy mouth and the colour of the very curly hair between the horns of bulls varies between orange, reddish brown to black. However, some Maronesa bulls have a reduced or lacking eel stripe, and some Maronesa cows also are coloured dark brown, in rare cases black; this is an unpleasant effect of breeders selecting against sexual dimorphism in colour. For some reason, many Iberian breeders apparently dislike the original sexual dimorphism of cattle and if this selection process isn’t counteracted by a program to conserve the primitive lineages of this breed, future Maronesa might get as uniformly dark or black as Sayaguesa.

This is what I imagine the curly hair between the aurochs' horns to look like
Bull with perfectly aurochs-like horns, albeit oriented too low
The horns of Maronesa are about the same size as in the aurochs, perhaps slightly smaller. The curvature resembles those of the aurochs almost perfectly in many bulls and also some cows, albeit being some 15-20° (just an estimation of mine) lower than in the average archetype. While some bulls have rather thick horns, the horns of most cows unfortunately are not as thick as in the aurochs, and the tips curve outwards in many cases, similar to a corkscrew. Nevertheless, individuals with inwards-facing horns of the breed surely are very helpful for effigy breeding.

Cow with inwards-facing horn tips
Cow with outwards-facing horn tips
Large bull with thick horns, short skull
Maronesa have, as do the possibly related breeds Barrosa and Arouquesa, a comparably short and concave skull, bulls in particular. Maronesa has a clear hump in many individuals (again, bulls in particular), though this hump is not quite as tall as in the Spanish fighting bull; some cows have a really athletic body, while the bulls tend to be not as high-legged. But in general Maronesa are more athletic than most Heck cattle, especially when kept under semi-natural conditions and when they are not fattened.
This breed is variable in size, but most individuals are not very big. Some are even as small as Highland cattle. Therefore, the size is something that has to be considered when choosing Maronesa for an effigy breeding program. However, some individuals still grow comparably big, and one bull which’s semen is used in Tauros Project allegedly reaches almost 160 cm at the shoulders.

Very aurochs-like cow in Faia Brava: proportions, colour and body shape look perfect to me.
If the horns were larger, more upwards- and inwards-facing and the skull more elongated (and probably the body size larger), that cow would look perfectly like an Aurochs to me
All in all, Maronesa probably is one of the most aurochs-like breeds in Europe thanks to its colour, horn shape (and also horn dimensions) and also proportions (at least in cows, the bulls are not that long-legged). The curly hair between the horns gives them a particularly wild appearance. Disadvantages of this breed are the mostly small size and the short snouts. The fact that their horns are very low is advantageous when crossing with breeds with very upright horns (mostly Steppe cattle).
Maronesa is a breed that has proven to survive well in the wild of Portugal, and is resistant to heavy rainfall and snow. And they are known to fight off wolves. A selection of good In my opinion, Maronesa is at least as desirable for rewilding as good Heck cattle, especially when supplemented with another breed that adds what is lacking in Maronesa. Maremmana for instance would improve the size, head shape and also result in more upright horns within the aurochs’ variation range. Add a bit Chianina and select carefully, and you get a very good stand-in for the aurochs.

Cows in the Netherlands, used in Tauros Project
Tauros Project has a herd of nice Maronesa in the Netherlands and is producing Maremmana x Maronesa crossbreeds at the moment. Let’s see what will come out of it, it will certainly bring interesting results. The Faia Brava reserve also has a herd of slender Maronesa that were released last year, and they will also be combined with other breeds. The herd did very well with the rough conditions in the reserve last year.

Here you have some nice videos of that breed (I would insert the videos themselves, but blogger doesn't find them): 


Literature

[1] Catarina Ginja et a.: Y chromosome haplotype analysis in Portuguese cattle breeds using SNPs and STRs. 2009.