It is a common misconception that domestic animals lost much of their capability of surviving without man. Because of that, some people might conclude that breeding-back should not emphasize the appearance of the animals but their surviving capacity instead, otherwise the result is a population that looks like an extinct animal but cannot survive in nature. But, as we painfully have learned, domestic animals of any species, be it dogs, cats, sheep, goats, pigs, cattle, donkeys, horses, camels or rabbits successfully survived and adapted to a life outside man’s custody. Abandoned or escaped pets/livestock flourished not only in the native range of their respective species, but also in ecosystems their ancestors never inhabited. Let’s focus on cattle and horses because they are the relevant species here.
There is a number of free-roaming horse populations in North America, such as mustangs, the Sable island pony, Chincoteague pony, Cumberland island horse, Nokota, the feral horses in British Columbia and a few more. The mustang is even legally protected. Most people might be familiar with the fact that these free-ranging horses descend from Iberian horses that have been introduced into the Americas during the last few centuries. The largest population of feral horses is found in Australia, where they are called Brumby and number up to 400.000 individuals. Brumbies prefer grassland with rich water sources while feral Australian donkeys tend live in arid savannas  – they show the habitat preferences of their ancestors.
|Feral Chincoteague horse|
|Brumbies in Australia|
Some pacific islands are home to feral horses as well. On the Japanese island Kyushu there is the Misaki-uma, a pony that dwells mountain regions. New Zealand is inhabited by the Kaimanawa horse.
|Misaki-uma in the Japanese upland|
The most unexpected and unknown place for feral horses is Africa. Yet there are indeed free-roaming populations in the Kondudo (Ethiopia) and the Namib Desert. They seem to be related to Arab horses .
All these populations I mentioned above (and this list isn’t meant to be complete) are outside the range of their wildtype, and the environmental factors in some of these regions are drastically different from those of their species’ native range. Now let’s move to feral horses of Europe.
Britain once was inhabited by feral pony populations that were the base for many of the native British pony breeds. The Exmoor Pony is the last remnant of these feral horses (the earliest historic reference dates back to 1036) that now largely lives a domestic or a semi-feral life. Britain is home to several other semi-feral pony populations, such as the Dartmoor Pony, New Forest Pony or feral Welsh Ponies.
|Feral Garrano in Portugal|
Some Iberian horses are similar to these British ponies and are considered members of the “celtic pony type”. The Garrano is such a breed and lives feral in northern Portugal. Moving eastwards, we have the Marismeno horse, found in the Doñana National Park, and the Camargue horse. The Netherlands are inhabited Europe’s second largest feral pony population, as about 1000 Koniks live in Oostvaardersplassen without major human interference. Central Europe does not have a true feral horse population today, but until the 1840 there was a feral breed called the Emscherbrücher (its remaining individuals were integrated into the Dülmen Pony stock). The Letea forest in the Danube Delta in Romania is inhabited by the Danube Delta horse. During the last years, this feral population flourished and now they are Europe’s largest feral horse population counting about 3600 individuals.
|Feral horses in the Danube Delta, Romania (Image source: virtualdobrogea.com)|
Interestingly, I realized that many feral horses have a brown/bay coat colour, but that doesn’t have to mean much.
Just like in the case of horses, there are feral cattle on nearly each part of the world. In North America, you have feral Texas longhorn in the Wichita Mountains Wildlife Refuge, and feral herds of Florida Cracker live in the Paynes Prairie. On Sapelo Island (Georgia) and Kauai (Hawaii) the descendants of abandoned dairy cattle still live there.
|Feral Corriente on Kauai|
Australia is home to the so-called Shrub oxen which are used for commercial hunting, just like their relatives on New Zealand.
|Feral cattle in Australia (Image source: huntaust.com.au)|
|Feral bull on New Zealand|
On Amsterdam Island, an island in the south of the Indian Ocean, feral cattle have been running around since 1871 and their number grew to more than 2000. They descended from usual French dairy cattle such as Tarentaise or Jersiaise and have developed a remarkable “wild” body shape. There are feral herds on the Seychelles and the Falkland Islands as well.
|Feral cattle on Amsterdam Island|
It shouldn’t be all too surprising that there are feral cattle in Europe as well. The longest history as a feral breed has Chillingham cattle. The earliest written account is from 1645, they suffered from severe inbreeding during the last century.
|Chillingham cattle (Image source: deptfordpudding.com)|
In Southern Europe, there are feral herds of the aurochs-like Maronesa breed, and semi-feral herds of Monstrenca in the Doñana National Park as well as semi-feral Camargue cattle. The Betizu breed is native to the Pyrenees and is very shy because it has been hunted for a long time . Nowadays there is a reserve in Navarre to preserve that breed. And of course, there are the more than 500 Heck cattle living with little human interference in Oostvaardersplassen.
|Feral Betizu bull (Image source: Wikipedia)|
To put it in a nutshell, cattle and horses apparently do not have any big difficulties in surviving in nature – many of these feral populations descend from usual dairy cattle or riding and working horses that one wouldn’t expect to come across in the wild. They survive because domestic animals have not been pampered by a life exclusively in sheds and masses of food for millennia as you might imagine. In fact, one could say that natural selection still played a role in the origin of many domestic animals that we know today, because the economic situation of farmers often made it impossible to protect their animals to the largest possible extent. In less industrialised regions of Europe there still are less-productive forms of agriculture where the horses and cattle mostly have to take care of themselves and only get supplementary food on some occasions. The harsh conditions livestock has to cope with creates so-called landraces that are adapted to their home range. It wasn’t all too long ago when this form of breeding livestock was common the developed countries of Europe and North America as well. Therefore, it isn’t surprising that a lot of breeds are capable of surviving without human interference. Some certainly do better than others, and some highly-derived and inbreed breeds might not be capable of doing so, but the majority of cattle and horses apparently is.
What does this all tell us about breeding-back? It teaches us that phenotypic aspects do not have to be neglected because of concerns on the surviving capacity of the animals as long they are healthy and genetically diverse, especially since breeding-back attempts mostly work with landraces.
-  Australian Government: Feral horse (Equus caballus) and feral donkey (Equus asinus)
-  Cothran, van Dyk, can der Merwe: Genetic Variation in the feral horses of the Namib Desert, Namibia. 2001
-  ABU info 06/07: Bunzel-Drüke, Scharf & Vierhaus: Lydias Ende - eine Tragikomödie