Guerrilla rewilding: urgent protest or dangerous gamble?

In early January last year police in the Scottish Highlands received reports of two Eurasian lynx (Lynx lynx) spotted near the small town of Kingussie. Four lynx in total had been released illegally in the vast and remote foothills of some of the Cairngorms’ highest peaks. The animals were quickly captured, although one died soon after. The following month Cairngorms authorities were dealing with another release, this time a drove of wild boar, found half a dozen miles away in the Uath Lochans area of the National Park.

The release of lynx – a predator not seen in the UK for more than 1,000 years – is perhaps the most extreme example yet of what has become known as ‘guerrilla’ or ‘covert’ rewilding, where individuals or informal groups release species into the wild without authorisation.

Other species, from wild boar to beavers to butterflies, have also been released in this way, and further releases are expected in the coming years. So who is doing this and why – and what impact might these rogue rewilders have on the ecosystems and the animals they wish to see flourish? 

Experimental ecology

Species reintroductions have a surprisingly long history and have not always been performed with the scrutiny we expect today. In 1922 Eurasian beavers (Castor fiber) were translocated from remnant populations in southern Norway to central Sweden, where the species had been eradicated by overhunting. Transported by sleigh, train, boat and even seaplane, the animals were released with minimal veterinary screening or post-release monitoring by modern standards[1]Jorgensen, D. Recovering Lost Species in the Modern Age: Histories of Longing and Belonging (MIT Press, 2019).. Yet the population established successfully and went on to recolonise major river catchments, highlighting the beaver’s role as a keystone species and ecosystem engineer.

In 1948 wildlife rangers in Idaho parachuted beavers in wooden crates into the remote Chamberlain Basin, a rugged landscape inaccessible by road, in the hope of restoring degraded wetlands and stream systems. Since then many more reintroductions have been performed around the world: the Arabian oryx (Oryx leucoryx), extinct in the wild by the 1970s, was restored through coordinated captive breeding and reintroduction in the Middle East; Père David’s deer (Elaphurus davidianus) was returned to reserves in China; and large-mammal reintroductions in southern Africa rebuilt populations following local extinctions 

The question today is less about whether reintroductions should occur, and more about how – and who decides.

Release regulation

In the UK licensed reintroductions have often lagged behind high levels of public enthusiasm for the idea[2]‘Third of Brits would reintroduce wolves and lynxes to the UK, and a quarter want to bring back bears.’ YouGov, London, UK (2020).. Regulatory pathways are politically vulnerable, cautious and frequently protracted. In the gap between ecological aspiration and institutional action, a parallel history has emerged, with individuals and informal networks releasing species without authorisation. These acts may or may not break the law, which is surprisingly inconsistent depending on the species or taxonomic group concerned. Even where laws are not broken, such acts are still deemed illicit if they occur without consultation and agreement from statutory organisations or local communities.

Guerrilla releases are sometimes framed as acts of protest, but they are better understood across a spectrum of motivations. At one end are small-scale, sentimental acts driven by affection or nostalgia; at the other are large, contentious interventions intended to force rapid coexistence in landscapes that have not been socially or institutionally prepared. Some releases are motivated by moral or ecological conviction, others by impatience, carelessness or even convenience, such as the desire to dispose of unwanted pets. Ecological knowledge varies widely, from sophisticated to limited. What unites these acts is not ideology but circumvention: the deliberate bypassing of governance, consultation and accountability.

Butterfly releases are one of the most subtle forms of guerrilla rewilding. Extirpated species such as the large copper (Lycaena dispar) and black-veined white (Aporia crataegi) were released covertly numerous times throughout the 20th century. Winston Churchill openly described attempts to re-establish black-veined whites near his home, making him, surprisingly, an early guerrilla rewilder. Today butterfly releases are more furtive, enabled by online trade in eggs and larvae. The low visibility of these acts can make them appear benign, but their cumulative ecological effects are poorly understood. Unscreened stock can introduce disease, provenance is often unknown, the requirement for metapopulations is usually disregarded and altered life-history traits may disrupt already stressed insect communities.

Eurasian goshawks (Astur gentilis) illustrate a different outcome. Extinct in Britain by the late 19th century due to persecution, they reappeared in the mid-20th century, strongly associated with releases and escapes linked to falconry. Full legal protection arrived in 1981, and today hundreds of breeding pairs occupy British woodlands and their presence is celebrated. Their history complicates simple moral narratives: an unsanctioned return that became, in effect, an accepted population, subsequently protected by law.

Beaver bombing 

Beavers sit at the centre of debates around guerrilla rewilding because they reveal both its ecological promise and its social cost. The practice of secretly releasing them into waterways in the hope of reshaping local habitats is known to some as ‘beaver bombing’ or ‘beaver black-ops’.

In Belgium in the 1990s, one man’s frustration with slow official action for nature prompted one of the most astonishing individual acts of covert rewilding known to date. Olivier Rubbers, then in his late 20s, transported close to 100 beavers from Germany to release them into Belgian rivers, borrowing his father’s car and reportedly using forged documents to obtain animals from breeders. “We wanted them all,” he later recalled[3]‘The secret movement bringing Europe’s wildlife back from the brink.’ codastory.com (June 2023)., expressing a belief that the moral case for restoration justified the means. These releases contributed to a national population recovery, but they also bypassed safeguards designed to protect animal welfare, social consent and public trust.

Beavers were returned to Scotland via a licensed, planned reintroduction in a western catchment, and an unlicensed population in the east, centred on Tayside, likely originating from escapes or deliberate releases. In the west, the releases were carefully governed, with health screening, genetic analysis, post-release monitoring and community engagement. The Tayside beavers, in contrast, became established within intensively farmed landscapes, forcing rapid, reactive responses around dam management, crop damage, compensation and conflict resolution. These animals were placed in the heart of a landscape that culturally was not ready for them.

The illegal release of Eurasian lynx into the Scottish Highlands last year was perhaps the starkest illustration of the risks of guerrilla rewilding. The individuals’ behaviour – poor hunting proficiency, inadequate avoidance of roads and settlements, and limited wariness of humans – was nothing like the behaviour of wild lynx, suggesting they had captive origins. Their movements brought them into close contact with the public, heightening anxiety about the risk to humans and livestock, and the welfare of released individuals, and further polarising the discussion around legal lynx reintroduction in the UK. Rather than advancing coexistence, such actions risk undermining public trust and the credibility of sanctioned reintroductions.

It is thought that there have been other illegal lynx reintroductions across continental Europe. Lynx have appeared far from established populations without telemetry data, release records or genetic documentation, raising persistent suspicions of unlicensed releases. In several cases, as with some beaver releases, guerrilla-rewilded individuals were later incorporated into formal monitoring programmes, blurring the boundary between informal and sanctioned reintroductions. While such actions may accelerate short-term recolonisation, research on large-carnivore recovery consistently shows that undocumented releases undermine transparency, compromise genetic planning, and erode social acceptance – factors critical to long-term persistence. 

Contested conservation

Even celebrated, government-led reintroductions can be contested. The Yellowstone wolf (Canis lupus occidentalis) reintroduction in the US, perhaps one of the most celebrated reintroductions in the world, has faced ongoing litigation since the late 1990s as state authorities, ranching interests and conservation groups seek to promote divergent visions for wolf management, and some question their legal status. These competing social narratives highlight the complexity of defining success in reintroductions.

All forms of reintroductions are, in effect, experiments in rebuilding populations. Founder number, relatedness, sex ratio and age structure determine effective population size and long-term adaptability. This is why formal genetic management exists, and studbooks and pedigree-based systems are standard in sanctioned programmes. At a continental scale, databases track the ancestry and genetic diversity of species such as European bison (Bison bonasus) and Eurasian beaver, enabling translocations that can relieve genetic bottlenecks through careful planning. These frameworks do not eliminate uncertainty, but they make it manageable.

Illegal releases invert this process. Instead of deliberate design, managers are left with forensic reconstruction: tracing the origins of the individuals that have been illegally released, trying to assess disease risk and deciding whether intervention is needed to prevent genetic collapse. This work is slow, expensive, often socially contentious and likely to divert hard-won resources from sanctioned programmes.

Modern populations of Eurasian beavers descend from a severe bottleneck, when numbers were reduced to approximately 1,000 individuals in isolated refugia. In Britain, genetic analyses reveal that covertly released founder animals originate from multiple European lineages, meaning that four of the five major beaver clades are now represented[4]Ritchie-Parker, H. et al. Genetic diversity analysis of beavers (Castor fiber) in England. Natural England Research Report NECR433 (2022).. This suggests either good fortune or well-informed guerrilla rewilders. It does not, however, remove the need for management to prevent further reduction of genetic diversity. Today, sanctioned beaver translocations in Britain rely on studbook-style systems to maintain diversity and avoid inbreeding.

Legitimacy is key

Critically, reintroduction success hinges not only on ecological factors, but also social and cultural ones. Seeing a beaver fell a tree, hearing a goshawk call in mature woodland or knowing that lynx could once again roam upland forests reshapes how people perceive landscapes and their own place within them. Awe and wonder are not incidental to conservation; they are among its strongest foundations, helping to temper human hubris and promote pro-environmental behaviours.

Yet these values must be cultivated through legitimacy. Guerrilla rewilding can generate attention and, at times, catalyse institutional change. It can also fracture trust, harden opposition and leave agencies managing crises rather than building durable coexistence. The tension it exposes is not merely between legality and illegality, but between legitimacy and illegitimacy in determining which species are allowed a future in our countryside – and on whose terms those decisions are made.

Goshawks were an unsanctioned return that became an accepted population, protected by law

Successful cases of guerrilla rewilding have not demonstrated that planning, genetics, welfare or engagement are unnecessary. Rather, they have revealed that legislation and policy frameworks have often been too cautious, too slow or too fragmented to translate evidence into action. In that vacuum, individuals have acted. Some have been careful and knowledgeable; others careless or driven by personal conviction rather than collective consent. The outcomes have been mixed, but the underlying message is consistent: where no credible pathway for recovery exists, informal ones will emerge.

In a nature-depleted country the desire to put missing species back is understandable. However, reintroduction is not only about ecological function or efficiency. It is about responsibility, to animals, to ecosystems and to people. Guerrilla rewilding poses a sharp ethical question: is urgency alone enough to justify bypassing collective decision-making?

The answer should not rest on outcomes alone, however successful some may appear.

Dr Joe Glentworth is a lecturer in Nature Recovery and Rewilding at the University of Manchester.

Dr Emma Cary is an honorary research fellow at the University of Aberdeen.

Dr Anna Gilchrist is a senior lecturer in environmental management and ecology at the University of Manchester.

Dr Ian Thornhill is a senior lecturer in planning and environmental management at the University of Manchester.

Acknowledgements: We would like to thank the students on the MSc in nature recovery, restoration and rewilding at the University of Manchester for the thoughtful debates that helped shape this article.

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