Not only are the horns interesting, the bulls are also much more long-legged and less massive than Heck cattle found in zoos (which is were they descended from). Morphology can be influenced by phenotypic plasticity, so these changes in body shape and proportions do not necessarily indicate a genetic change in these cattle. In the case of the horns, however, I see no way how phenotypic plasticity can influence the horn curvature and orientation relative to the snout, thus I think we see genetic changes here. A change in allele frequency as a result of natural selection is the population genetic definition of evolution. Thus, we might see evolution at work here.
In how far are the horns of these young bulls different? For once, they face clearly forwards in a 70 to 60° angle relative to the snout, which is identical with the horn orientation of the European aurochs. Earlier Heck cattle from the reserve (which can be seen on older photos easily available on the internet) never have forwards-facing horns, at least not on the photos I have seen so far, which are quite a lot. Furthermore, while the horns of early Oostvaardersplassen Heck cattle are curved rather straight, the horns in these bulls are curved more clearly. They do not curve inwards as strongly in the aurochs by far, but a tendency of the horn tips to grow a curve is there. This can also be seen, even more clearly, in some of the cows in the reserve (the photos aren't online anymore, unfortunately). To me, this suggests that the horn shape of the Heck cattle in the Oostvaardersplassen reserve is evolving. Precisely, evolving to a more aurochs-like horn shape.
This is not surprising, as the horn shape of the aurochs probably had a purpose. Their strong inwards-curve enabled the bovine to push and pull the opponent during a fight, and the fact that they faced forwards and not upwards or downwards was likely functionally advantageous as well. If the horn shape of the Heck cattle in the reserve is indeed evolving, which can only be proven by gathering photos of individuals from the early years till today, it would endorse the following thoughts:
1. the horn shape in cattle/aurochs has a function and the horn shape of the aurochs was not a coincidence
2. This has an impact on the evolutive fitness of the individuals (the more functionally advantageous the horn shape the higher the likelihood to win an intraspecific combat for breeding rights, feeding grounds etc.)
3. Eventually, the wildtype horn shape will develop in a cattle population that is exposed to natural selection, especially intraspecific selection
The more genetically diverse the population, the faster the changes evolve (Fisher's fundamental theorem). Since Heck cattle is a mosaic breed based on many different cattle breeds, the wide range of phenotypes displayed by the individuals might have enabled the adaption process to become visible quite fast.
I postulated that natural selection will make a variable cattle population in the wild more aurochs-like because wildtype traits are functionally advantageous multiple times on my blog, and I think these recent photos of Heck bulls at the Oostvaardersplassen reserve endorse this idea when you compare them with earlier individuals of the same population. In my opinion, the Heck cattle at this reserve are a valuable example for dedomestication.
It is no secret that the original founding population of the Heck cattle at the Oostvaardersplassen, being ordinary Heck cattle from various locations, were not prime examples for aurochs-likeness. Yet, natural selection produced at least partly aurochs-like horn phenotypes after 40 years of intraspecific competition. This fits my idea that natural selection will "refine" any "breeding-back" product once released into the wild - if it worked on the mediocrely aurochs-like founding population of Oostvaardersplassen, imagine what kind of phenotypes might be produced by 40 years of natural selection with more aurochs-like cattle.
Are there many bulls in every herd?
ReplyDeleteAre the cows bred to the winners of bulls fighting each other?
Bulls fighting each other get injured. If the herds are kept with just one grown up bull, then there can be no natural selection for any trait of the bulls. Then it is human selection.
The population at Oostvaardersplassen is completely free of selective breeding, the animals breed for themselves, therefore there is intraspecific competition as written in the post.
DeleteHey Daniel Foidl can you do the one blog about Aurochs in Bosnia and Herzegovina ? I have the many examples .In the Cazin region, wild cattle are called Garonja (Slavic name for black bulls) , which actually resembles a real Aurochs ( Bos Primigenius ) . In Bosnia and Herzegovina there are toponyms for Aurochs. For example, Turija in Bihać (Una river), Turijak village near Višegrad (Drina river), Turjak near Banja Luka, Vrbas river, Turić near Pelagićevo (Sava river). Aurochs as animal is very common in Bosnian mythology as giant black bull who holds the whole world . In Bosnia it is very common for person who is strong to be said " Jak si kao bik " ( translated as You are strong as bull ). In National Museum of Bosnia and Herzegovina there are few fossils of Aurochs found in Northern Bosnia in coast of Sava river .
DeleteI suppose a limited environment could also lead to island effects like small bodies, small brains and reduced reproduction but perhaps less so than when living on a farm.
ReplyDeleteYes, the island effect is definitely a thing there, in a video showing the cattle next to a car I got the impression that they already have decreased in body size. This trend will likely continue.
ReplyDeleteThis may be a long-lasting problem if bred back cattle are never allowed in the wild. Artificial selection will always be required.
ReplyDeleteThe island effect is a problem for conservation in general. Often it is not possible for large species to have one large, continuous distributional range but they are confined to ecological islands (reserves etc.). If that lasts for a long period of time, it will certainly influence the animals' genome.
DeleteWould the main cause of the Island Effect in Oostvaardersplassen be the regular lack of forage for grazing in winter and spring causing starvation and stunting developing fetuses?
DeleteThe lack of space and ressources would favour smaller animals, as they need less of them, especially in an environment lacking predators as in the Oostvaardersplassen.
DeleteIt is worth noting that predation would have a much greater effect on some species than others, especially if we're just talking about wolves. Red deer are controlled to an extent by predation but bovines typically are not and for equids it is very situational. Were predation present in the Oostvardersplaasen, starvation would still occur, it would just be a greater limiter for the larger herbivores than the smaller ones. This might lead to some competitive release for cattle, potentially allowing for larger body sizes.
DeleteOn Tue 21 Jun 2022, Phoebe Weston wrote in "The Guardian", an English newspaper, that recent management in the Oosvaardersplassen involves removing surplus animals so the population is kept below a chosen level. I wonder if those doing that work might be practicing selection to favour more Aurochs-like horns.
ReplyDeleteI guess removing means they cull them. That's a bit comically: they kill them so that they don't die in the reserve. I don't know if they pay attention to the aurochs-likeness of the cattle.
DeleteThe article doesn't say refer to any kind of selection. From what you wrote above, they do not seem to be trying to increase the size of the cattle. Dominic Berridge.
DeleteHey I found some other great photos from a bull with great shaped horns even better than these.
ReplyDeleteWhere are they?
DeleteIt is likely that horn shape of wild breeding cattle will evolve towards Aurochs-like, because horns of wildtype shape were probably optimized for intraspecific fighting, and animals with those horns will breed better. It would be interested to check, whether domestic cattle with aurochs-like horn shape are more advantageous in fighting with other cattle
ReplyDelete