In a few nature reserves in a few locations around Europe, the air reverberates with rumblings and ruminations relayed from the ecological past.
In parts of the Netherlands, Croatia, Romania, Spain and Portugal, an extinct species has been reincarnated for the first time in centuries. It’s a species whose domesticated descendants, second only to dogs, are probably the most familiar animals to us, and yet for it to look and behave as nature intended in a wild ecosystem is now beyond most people’s imagination. But that’s exactly what the Tauros Programme aims to achieve by breeding back wild cattle.
The Eurasian aurochs – one of three subspecies – was widespread across Europe and Central Asia following the last Ice Age, but the spread of agriculture caused its populations to decline and fragment, driven into less favourable habitat by competition with human settlements and their domestic livestock. It was extinct in Britain by around 3,500 years ago, but persisted in the forests of Europe for considerably longer. The last known individual died in Poland in 1627.
The Tauros Programme
Begun in 2008, the Tauros Programme is a collaboration between the Dutch organisations Stichting Taurus and Ark Rewilding Netherlands, as well as Rewilding Europe. It’s using selective breeding of domestic cattle, informed by the latest genomic data, to back-breed a wild cow as similar as possible to the ancestral aurochs. They’re calling this cow the Tauros, to distinguish it from its extinct ancestor, though this distinction should be mainly semantic.
Among the great variety of domestic European cattle, some older breeds have remained relatively close to the aurochs both genetically and physically. A few of these were selected for use in the Tauros Programme, and individuals were transported to the Netherlands for its initial phase, with their first cross-bred calf born in 2010.
The spread of Tauros
In 2011, the first complete genome was sequenced for the aurochs, which provided an accurate genetic reference against which to compare the cattle breeds used. The programme could subsequently confirm, for instance, that the pajuna cow of Andalucia not only looks pretty close, but is also the closest domestic breed genetically to the aurochs.
Today, breeding herds of Tauros are spread across five countries to insure against disease or natural hazards, with parts of the Netherlands having reached the seventh generation of breeding. Some private landowners in Britain who are rewilding their land are now considering introducing Tauros herds, such as Drumadoon estate on the Isle of Arran.
Why aurochs? How they differed from bison
So why bring back the aurochs? Europe’s large wild herbivores were keystone species, meaning they had a disproportionate impact on their habitat. Much like related bison, the grazing and browsing of the aurochs helped to disturb the vegetation, slowing the succession towards woodland and maintaining more open areas in the landscape. Their trampling and scraping of the ground created patches of bare soil ideal for colonisation by pioneer plants, and for use by insects to burrow and lay eggs.
Their dung was a food source for a range of insects – particularly beetles – as well as a ready lump of fertilizer for seeds dispersed via their gut and fur. Their carcasses provided an entire ecosystem for insects and scavenging birds and mammals, while leaving behind a ‘decomposition island’ of nutrient enriched soil which gave rise to unique patches of vegetation.
Though they occupied a similar niche, the feeding ecology and habitat use of the aurochs was distinct from bison. They likely spent more time in lowland river valleys and consumed a higher proportion of grass compared to the more mixed bison diet. While cattle will also eat a range of woody vegetation, they tend to stick to leaves and twigs, whereas bison consume a higher proportion of bark in the winter. It would therefore be incorrect to see recovering populations of European bison as sufficient to stand in for cattle.
Why not use cattle instead?
But why back-breed new aurochs instead of just using free-roaming domestic cattle as a proxy, as they do at Knepp Wildland in Sussex and other rewilding projects? There are likely several reasons.
The Tauros are larger than domestic cattle, with less conspicuous coat colouration and larger horns, which helps them to defend against predators – something domestic cattle rarely have to do even in many rewilding projects. The oversized udders of most domestic breeds make them ungainly and could be vulnerable to injury in a wild ecosystem, whilst inhibiting their evasion of predators. If cattle are to be reintegrated into properly rewilded landscapes in the long term, they must be fit to live alongside Europe’s recovering populations of wolves and bears.
Recognising the Tauros as a wild species
An additional aim is for the Tauros to be recognised by the IUCN as a wild species, meaning they’ll be free to roam over large landscapes without the regular ear tagging or health checks required for domestic cattle.
Even at the relatively small Knepp Estate, Isabella Tree has written about the challenge of rounding up their free-roaming cattle for tagging and TB testing, which is not only stressful for the animals, but takes a lot of time and resources.
If we imagine a future where the Weald to Waves project establishes a continuous wildlife corridor through Sussex and allows herbivores to roam throughout much of its length, then using the English longhorn cattle currently present at Knepp would be an administrative nightmare.
Testing Europe’s commitment to rewilding
This last issue touches on what will ultimately be the key determinant of success for the Tauros Programme. Can Europe accept this now so foreign concept of wild cattle requiring no human management? The Tauros, bred from domestic cattle to replace the wild aurochs, is arguably a perfect bovine avatar for rewilding in general; restoring ecosystems as far as possible towards a point where they can look after themselves.
The next few years of this programme won’t just test the Tauros at living in the wild, but also test Europe’s commitment to rewilding.
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