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Thursday, 5 February 2015

Dedomestication series Pt. IV: What existing free-ranging cattle are like


For part I, go here, for part II, for part III
In the previous part of the dedomestication series we looked at the evolutionary/phenotypical chances that might evolve when a feral cattle population is exposed to all levels of natural selection and reproductively isolated. To sum up my predictions:



- The trunk would become shorter and the legs longer, enabling a higher manoeuvrability. The manoeuvrability is also increased by developing a slender waist and high shoulder spines forming a “hump” that all wild cattle have.

- This hump is the result of intra- and interspecific fights, as larger shoulder and neck muscles are advantageous for this.

- Horns with the so-called “primigenius spiral” would be most advantageous in intraspecific combats. Also, an orientation not too low or too high relative to the skull and a size that is not too large or small.

- Basically, the larger the body size the more evolutionary fit. But body size is also regulated by space and food availability.

- Sexual dimorphism, both in size and colour, would increase.

- Colour has the least influence on evolutionary fitness. It might become slightly influenced by pleiotropic effects, sexual selection and predation, but many domestic colour variants probably would have little to no effect. It would take a very long time until the cattle population is coloured homogeneously thanks to drift and bottlenecks, depend largely on coincidence and what colour alleles are already present in the population.

- Risky, feisty and energetic behaviour is advantageous for achieving dominance and defending against predators.



For details, please have a look at part III.

The purpose of this post is to examine existing, feral cattle populations and to see whether these confirm the my predictions or not. But it is important also to look at the environment and selective pressures they are exposed to and what the starting population was like, otherwise we might draw wrong conclusions. For example, if a population did not develop aurochs-like horns because none of the founding animals had such, it does not necessarily contradict my prediction on horn shape.



The first free-ranging cattle population that comes to most people’s mind are Chillingham cattle. I already did a more extensive post on these cattle when I visited them in 2012. They never were completely feral and free-roaming, but always kept in the game park of Chillingham, and they never were free of artificial selection. For example, it was selected against individuals with pink noses, and during epidemics the sick animals were culled to prevent the die-off of the population (that’s why they are genetically homogeneous today). But they did not have any other medical care, and they reproduce freely. They do not have sheds and are not supplemented with additional food. Although they mate for themselves and therefore sexual selection applies, the horn shape is only remotely aurochs-like. This might partly be the result of genetic bottlenecks (indeed a small sample of older skulls, some of which I photographed, show a more aurochs-like curvature). We can only speculate what the horns of the founding population looked like. The body shape does not look like one would expect from feral cattle at all, they look rather domestic. Even escaped farm cows develop a more athletic body. Also, despite being fully exposed to the climate, their dewlaps and udders are still relatively large. These two facts are mysterious to me. Nevertheless, their behaviour is what I would expect. They have a strict hierarchical order in their herd, and the bulls are rather aggressive towards each other and carry out brutal fights regularly. The sexes are not separated, what is not a natural state for cattle but a result of the confined space. The limited space in combination with the lack of supplementary probably is also the reason for their small size. The bulls’ weight is only about 300 kg, and the cows’ little below. Richard Marsh, the cattle warden, told me that they got a little smaller over time, what confirms the “Island effect”.



The Amsterdam Island cattle, which existed from 1871 to 2010 when they were unfortunately exterminated, were a particularly interesting population. They lived in reproductive isolation and without any human care. Their ancestral breeds were Jersey cattle, Tarentese, Grauvieh and black pied Breton cattle. It was reported around 1900 that they had a hump (I suppose not the zebuine hump but that of wild bovines was meant) and did not behave nervous but interested and cautious towards humans, like cattle in grazing projects. The fact that they had a hump is confirmed by contemporary photos. Not as large as in the aurochs, but definitely there. Their body was slim and elegant. Seemingly most of them had an aurochs-like colour, what is not surprising considering that most of the founding individuals must have had a wild-type base colour. White spots apparently were not common, probably because they are recessive and were not common among the founding breeds. Based on the photos on the web, no individual had aurochs-like horns. The reason for that very likely is that none of their ancestral breeds have horns that would enable a fast development of the “right” curvature and size. Amsterdam Island cattle were small as well. With a male adult weight of 390 and a female one with 280 kg, the sexual size dimorphism was larger than in Chillingham cattle.  



Betizu are a Pyrenean breed with an enigmatic history, but it is clear that they have been living completely feral for a long time. They are very shy because they have been hunted. Betizu are known to be very rusting and resistant to the climate of their habitat (not surprisingly). Bulls are 130 cm tall and weight 450 kg, cows 110 tall and 325 kg, so they are a small breed as well and have well-developed sexual size dimorphism. Their colour is a uniform light-brown – I don’t know if they are homogeneous as a result of living feral or because their founding population was quite uniformly coloured already, but I prefer the latter explanation. The body of the free-ranging ones is slim and athletic, especially the bulls have a very muscular build. They do have a hump, but not a very large one. Udders and other appendages usually are small. The length of the skull varies from “normal” to elongated. Their horns are not aurochs-like; their size is mediocre and many have lyre-shaped ones or straight outwards-facing ones.



Cherikow, Sanak and Chirikof are Islands in the north of the Pacific that are inhabited by interesting feral cattle. Their ancestral breeds are mainly Highland, Yakut and Hereford. With the exception of the latter, these breeds are ecologically very well-suited for such a habitat, but the body shape of all three is typically domestic. I won’t go much into detail, but looking at some photos, it is apparent that these cattle have a more “athletic” body than their ancestral breeds, their trunk is shorter and they look somewhat more agile. Some of them have forwards-facing horns, but that’s not necessarily a result of selection because both Highland and Herefords have horns that also might face forwards or downwards.



There are also feral or free-ranging cattle on New Zealand and Hawaii. I don’t know much about their history and there is not much to say about their looks except that they look more athletic and usual farm cattle.



Oostvaardersplassen is an interesting population because it has been reproductively isolated and exposed to natural selection for about 30 years (what makes about 10 generations at maximum). No medical care, no supplementary food, and free reproduction. Predators absent. I already wrote a lot on OVP in other posts: http://breedingback.blogspot.co.at/2013/09/heck-cattle-at-oostvaardersplassen.html



Please take a look at those posts so that I do not have to repeat my self too much; but I will sum up the most important things: a number of individuals show horns with a decent inwards-curve that is not present in any un-crossed Heck cattle outside the OVP, also there seems to be a tendency to horns facing more forwards in some individuals; numerous bulls but also a few cows have a hump, in some specimen as large as in Lidia; the muscling and mass of the body varies, but some are as athletic as Lidia; most individuals have the usual head shape of Heck cattle, but it is very spectacular that some cows obviously developed snouts as long as in Sayaguesa. I don't know if this is the result of developmental cascades or phenotypic plasticity, like in the case of feral pigs. A 1:1 relation between trunk length and leg length in bulls is not uncommon. The population at OVP shows basically all colour variants present in Heck cattle. Based on the photos and videos that I have seen (and those are a lot), I would say that two thirds have an accurate wild type colour without dilutions, one third has a more or less diluted colour (rough guess). White spots are no rarity. It cannot be said with certainty how strong the sexual dichromatism is because we cannot know if a black bull inherits black cows or accurately coloured brown cows and so on. But I wouldn’t say that the sexual dichromatism appears to be higher than in other Heck herds. Judging from the photos, size dimorphism certainly did not increase, if anything it might have gotten slightly reduced. Based on their size relative to the horses, which should be 130 cm tall at the withers, they definitely did not get larger than other Heck cattle – if anything, I suspect smaller.

Many individuals at the OVP look just like any other Heck cattle, which is not surprising considering the time they have been living there so far. But it is undeniable that the population is in a phase of evolutionary change.



Slikken van Flakkee there is another interesting Dutch population. Just like the cattle at OVP, they do not get supplementary food and are allowed to breed for themselves without artificial selection. Only at the beginning the managers selected for upright horns because of an alleged risk of injuries (Margret Bunzel-Drüke, pers. com.), which is total nonsense. They have been introduced in the early 80s as well.

Like in the OVP, many of them have a greyish tint. I didn’t see many animals with spots so far. There are still some fat and short legged bulls, some individuals also have a hanging spine, but we see a similar trend as in the OVP. There are a number of bulls with a really slender and athletic build, i.e. short trunk and long legs, many of them have a hump and a slender waist. There is an impressing video of two bulls fighting in the reserve (https://www.youtube.com/watch?v=gWTY5IY__mk), look at their swift movements. Looking at other videos showing the cattle of Slikken van Flakkee, I would say that body shape and proportions of has underwent the same development as those of the cattle at OVP. I don’t know if those at S.v.F. have been reproductively isolated all the time, but even if there has been further Heck introduction, it is not an explanation for that body conformation.  



All in all I would say that the existing populations of cattle outside human custody confirm my predictions only in part. OK, none of them have been living under all the circumstances I assumed for my predictions in the previous posts and for a sufficient amount of time, but still. But what I can say is that all of the cattle develop a more muscular body and aurochs-like proportions with a more or less pronounced hump (with the curious exception of Chillingham cattle). I don’t know how much of that is inherited or phenotypic plasticity, but I think the latter plays an important rule concerning the muscles (f.e. look at this escaped Fleckvieh cow after straining for a few months: http://image3-cdn.n24.de/image/1348414/1/large16x9/tsz/kuh-yvonne-auf-gnadenhof-in-bayern-eingetroffen-image_620x349.jpg). How much plasticity affects the proportions and the hump is an open question to me, but I think that heredity is more important here. Genetics do have an influence on body shape, if you take a look at the fat bulls that are still around in OVP under the same environmental conditions as the swift and athletic ones. So the changes in body shape and proportions should be at least partially the result of an evolutionary process.

There are almost no examples of a trend towards aurochs-like horns. One explanation might be that the founding individuals of those populations did not have horn shapes that made it easy for such horns to evolve, or that a too limited variability requires a rather long time (see Fisher’s fundamental theorem). The only clear example of evolving aurochs horns is Oostvaardersplassen, whose founding population likely was very diverse regarding horns, where some individuals have horns curving more inwards or facing more forwards than in any other un-crossed Hecks. Another possible example are (were) Chillingham cattle, of which some individuals of the past had quite aurochs-like horns (and some still have) that might have become lost due to the several severe bottlenecks.

The fact that all those free-ranging cattle are small or comparably small, regardless of if they descend from founding breeds that were of small size already (f.e. Chirikov Island), confirms the island effect.

The colour of most of the free ranging cattle is totally heterogeneous and seems to be hardly influenced if at all by natural selection – this is what was expected. The only exceptions are Betizu and Chillingham cattle. In Betizu, die founding individuals might already have had that colour because rural cattle from that region have the same colour (guess), and in Chillingham cattle this is definitely the result of artificial selection: the nobility preferred white cattle, and those with black noses over those with pink noses.



You probably realized how speculative my conclusions are here.

For the last part of the series, go here




3 comments:

  1. Hi Daniel,

    wäre es möglich das Du mir Deine Mail-Adresse postest an >> info(ät)cs-b.info. Sehr gerne würde ich mich mit Dir auf Deutsch unterhalten. Seit 40 Jahren beschäftige ich mich mit Vererbung, als Laie (Fische und Vögel). Einige meiner englischen posts sind auch daneben geraten, weil mein englisch einfach nicht reicht.

    mfg Hans

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    1. Mein Mailprogramm sagt leider, dass das keine gültige emailadresse ist... oder war das nicht als Emailadresse gemeint?

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  2. Hi Daniel,

    Maybe in your prediction you underestimated the role of predation? During the evolutinary develpoment of the aurochs, the main preditors of such large beasts would probably be lions and sabretooths. I would think this would be responsible for size, hump and horn shape to a large extent?

    Cheers,
    F.

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