Wildlife
The Mouflon Problem: An Introduced Sheep in a National Park
In 1971, someone released a herd of wild sheep onto Tenerife. Mouflon, to be precise: stocky, reddish-brown animals with curved horns, native to Corsica and Sardinia. The intention was straightforward: create a hunting population on an island that had none. More than five decades later, those sheep are still there, grazing plants that evolved in a world without large herbivores, and the park that was created to protect those plants is caught in a conflict it never asked for. The mouflon problem is a textbook case of island conservation biology playing out in real time, and it has no clean solution.
The 1971 introduction
The mouflon (Ovis aries musimon) is not native to the Canary Islands. Before 1971, the only large mammals on Tenerife were domestic ones kept by farmers. Wild game for hunting was absent, and the island’s hunting community wanted something to pursue. Mouflon were a logical choice: hardy, adaptable to rough terrain, and already successfully introduced to several European mainland areas.
So they were brought in and released, mostly into the highlands that would later become the Teide National Park. The park itself had been established in 1954, but the conservation ethos of the 1970s was different. The idea that an introduced herbivore might damage an ecosystem that had evolved without one was not at the forefront of anyone’s thinking.
The mouflon population grew. They found the high-altitude volcanic landscape perfectly habitable, with enough sparse vegetation to sustain them. The park’s boundaries offered no barrier to a sheep that could walk wherever it pleased.
What mouflon eat
The high-altitude flora of Teide evolved in isolation. The plants that grow above 2,000 metres on Tenerife developed without any large browsing mammal present. No deer, no wild sheep, no goats. The only native land mammals on the island before human arrival were bats, shrews, and a few rodents.
That evolutionary history matters because it left these plants without defences. They have no thorns, no unpalatable chemicals, no low-growing growth habit designed to evade a grazing mouth. They simply grow, and when a mouflon walks up and eats them, they have nothing to stop it.
| Plant species | What happens when mouflon graze it |
|---|---|
| Spartocytisus supranubius (retama del Teide) | New shoots eaten; mature plants survive but regeneration collapses |
| Echium wildpretii (tajinaste rojo) | Flowering stalks bitten off before seed set; monocarpic plants die without reproducing |
| Viola cheiranthifolia (Teide violet) | Entire plants consumed; the summit-cone endemic is particularly vulnerable |
| Various alpine grasses and forbs | Grazed to the ground; soil erosion increases where cover is lost |
The damage is most visible in the retama del Teide, the white-flowered shrub that dominates the subalpine zone. In areas where mouflon have been excluded, the retama grows thick and tall, forming a dense shrubland. In areas where they graze freely, the plants are stunted, sparse, and often missing their new growth entirely.
Rabbits, also introduced to the island, compound the problem. They graze the same plants at a lower level, eating seedlings that might otherwise replace ageing shrubs. Between the two, the park’s endemic vegetation faces pressure from above and below.
The exclosure evidence
The standard way to demonstrate grazing impact is a fenced exclosure. Teide National Park has several of these, and the contrast is stark.
Inside the fence, the vegetation is visibly denser, taller, and more diverse. Retama shrubs flower and set seed. Tajinaste rojo sends up its full flowering spike, reaching two or three metres, without being bitten off. The soil surface is covered with leaf litter and moss. Outside the fence, the same species are present but reduced, nibbled, stunted, struggling to reproduce.
The exclosures are not a solution. They are a demonstration. They show what the high-altitude ecosystem would look like if mouflon were removed entirely, and they make the conflict harder to ignore.
The culling controversy
If the ecological case against mouflon is clear, the practical and ethical case for keeping them is equally real. The animals have been on the island for more than five decades. They are an established part of the landscape. Visitors see them, photograph them, and often enjoy the sight of wild sheep moving across the volcanic slopes. They have become, in a sense, part of the place.
The hunting community that originally wanted them introduced has maintained an interest in their presence. Culling programmes have been contested legally and politically. Animal welfare groups have objected. Local hunters have argued that the animals belong there now. The park administration has found itself in the middle, its statutory duty to protect endemic vegetation pulling one way, and public sentiment and legal challenge pulling another. The result is a situation that has dragged on for years, with no resolution in sight. The mouflon are controlled but not eliminated. The damage continues.
A textbook island problem
What makes the mouflon case instructive is the pattern. It is the same story repeated on islands around the world: an introduced herbivore arrives, finds no predators and no co-evolved defences in the plants, and proceeds to reshape the ecosystem. Goats on the Galápagos. Deer on New Zealand. Rabbits on Macquarie Island. And mouflon on Tenerife.
The pattern is well understood. The solutions are not. Eradication is possible, but it requires political will, public acceptance, and a clear legal mandate. On Tenerife, none of those are straightforward. The mouflon are not an invasive species in the sense of a recent arrival that can be straightforwardly removed. They are an established population with a history and a human constituency.
What visitors actually see
A visitor walking the trails of Teide National Park will almost certainly encounter mouflon. They are most common on the lower slopes of the volcano, around the Montaña Blanca area and the trails leading up toward the Altavista refuge. They are also seen on the caldera floor, grazing in the Llano de Ucanca and around the Roques de García.
They are not shy. Mouflon in the park have grown accustomed to human presence, and they will often continue grazing as walkers pass within a few dozen metres. The animals themselves are handsome, with rams carrying curved horns and ewes smaller and more lightly built. Their coats change colour with the season, reddish in summer, greyer in winter. A group of mouflon moving across a volcanic landscape is a striking sight. It is also, from the perspective of the park’s vegetation, a problem in motion.
What a visitor will not see, unless they look closely, is the damage. The stunted retama. The missing tajinaste spikes. The bare ground where seedlings should be. Those are visible only to someone who knows what to look for, or who has seen the exclosures and understands the difference.
The long view
The mouflon problem on Tenerife will not be resolved quickly. The legal and political obstacles are real, the public attachment to the animals is genuine, and the ecological imperative to protect endemic vegetation is not going away. The park administration continues to manage the population through controlled culling, but the numbers are not public, and the effectiveness of the programme is debated.
What is clear is that the mouflon are here to stay for the foreseeable future. The question is not whether they will be removed, but whether their numbers can be kept low enough to allow the endemic flora to regenerate. The exclosures show that it is possible. The challenge is extending that protection beyond the fence lines.
For the visitor, the mouflon remain one of the most visible large animals in the park, and one of the most photogenic. But they are also a reminder that national parks are not wilderness preserved in amber. They are managed landscapes, and the management decisions are rarely simple. The mouflon problem is conservation in its real, messy, human form.