The rewilding charity, “Trees for Life”, is planning to release a herd of tauros to their Dundreggan estate in the Highlands. These animals have been bred to fill the environmental niche left behind by aurochs – a species of large wild cattle native to much of Europe and Asia that became extinct in 1627.
Historically, aurochs were a keystone species, meaning they had a large impact in creating an environment upon which other species depended. Through grazing, aurochs herds would create open spaces amongst wooded areas, providing a habitat for other animals. These herds would also fertilise the soil with their dung and disperse seeds through migration. Additionally, during their mating season, aurochs bulls would create grassless “bull pits” by kicking sand and dust at their rivals, providing a habitat for pioneer plants – those which can germinate in barren areas.
Trees for Life hope that their herd, initially consisting of up to 15 tauros, will aid their rewilding efforts by fulfilling a similar keystone role to that of aurochs historically. Indeed, with this goal in mind, the Tauros Programme set out in 2008 to create a self-sufficient species that could fill the aurochs’ environmental niche – but how exactly did they create these aurochs-like tauros?
As almost all domesticated cattle are descended from aurochs, and with particular breeds from remote areas of Italy, Spain, and the Balkans minimally diverging from aurochs, one option for the Tauros Programme would have been to simply release these domesticated cattle into the wild and let natural selection “rewild” them. However, this option would take millennia, and the resulting animals would not resemble aurochs in looks, behaviour, or genes – as the evolutionary pressures that created aurochs do not exist in the modern landscape.
Instead, the program considered cloning aurochs from original DNA. This process would have involved extracting aurochs DNA from a frozen sample, then implanting it into an egg of a modern species. Whilst this would produce genetic aurochs, the process would be expensive, and the programme feared that the resulting cloned herd would lack genetic diversity.
Therefore, the programme settled on a process of “back-breeding”, which would involve selectively breeding individuals with the desired aurochs-like traits. However, unlike traditional breeding, the traits selected would be those which made the animals wilder. This process would be cheaper, quicker, and result in more genetic diversity than the alternatives.
Having started back-breeding certain cattle breeds which displayed aurochs-like characteristics, the programme as of 2022 was on their fifth generation of calves. However, one challenge the programme faces is getting their tauros recognised as a distinct and wild animal by the International Union for Conservation of Nature and relevant national authorities. Yet despite this, there are currently 600 tauros in herds across six countries – and it looks like Scotland might soon become the seventh.
Illustration by Rebecca Tate