Rewilding

Rewilders’ Wolf Howlers

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BY CALUM CAMPBELL & NICK PEARCE

The prospect of reintroducing wolves (Canis lupus) to the Scottish Highlands has become a recurring topic in environmental discourse, frequently accompanied by claims that this measure would naturally resolve Scotland’s deer management challenges, restore ecological equilibrium, and even contribute substantively to climate change mitigation. While these arguments possess considerable intuitive appeal and have garnered significant public support, a rigorous examination of the available scientific evidence, historical precedents, and practical realities reveals a far more complex picture—one that the prevailing rewilding narrative frequently overlooks or misrepresents.

A common refrain in the wolf reintroduction debate is the assertion that wolves are necessary to reduce Scotland’s deer numbers. However, this oversimplification ignores important nuances in deer population dynamics.

Open range red deer (Cervus elaphus) numbers in Scotland have actually been decreasing since the late 1990s to early 2000s, when populations were at their peak. The challenge is more specific: woodland deer populations, encompassing red, roe (Capreolus capreolus), and sika (Cervus nippon) deer, have risen, primarily due to poor forest design that renders effective deer management difficult. Additionally, roe deer numbers are increasing in the Central Belt and urban areas, where wolf reintroduction would be impractical and potentially hazardous. The assertion that red deer in Scotland have “no natural predators” is also demonstrably misleading; both golden eagles (Aquila chrysaetos) and red foxes (Vulpes vulpes) target red deer calves, demonstrating that a natural predation dynamic already exists, albeit not at the scale some rewilders might desire.

One of the most instructive case studies in wolf-deer dynamics comes from Alaska, where a large-scale experiment on Coronation Island provides a sobering counterpoint to optimistic predictions regarding predator-prey equilibrium. In 1960, the Alaska Department of Fish and Game released two pairs of gray wolves onto the island to study their effect on the abundant Sitka black-tailed deer (Odocoileus hemionus sitkensis) population. The results were dramatic and highly instructive. By 1964, the wolf population had peaked at thirteen animals, with deer remains constituting approximately 95% of their diet. However, this intense predation proved ecologically unsustainable. By 1966, the deer population had crashed, leaving only three surviving wolves. Scat analysis revealed a stark shift in foraging behaviour: deer consumption dropped by over half, forcing the wolves to subsist on marine invertebrates, birds, and rodents. Perhaps most tellingly, six out of one hundred scat samples contained wolf remains—unequivocal evidence of cannibalism driven by starvation. By 1968, only a single wolf remained alive on the island, and by the 1980s, wolves were entirely absent while the deer population had naturally recovered. What remains particularly puzzling is that the wolves did not swim the 1.5 kilometres back to the mainland to survive, suggesting either a remarkable territorial fidelity or an inability to perceive the island’s limitations in advance. This experiment demonstrates that wolves do not and cannot regulate their own numbers in a closed system; they will consume their prey base to the point of collapse before turning to alternative food sources, including conspecifics. The fate of Scotland’s wolves in a similarly constrained environment could mirror this pattern, but with the added complication of livestock predation when deer become scarce.

The Yellowstone wolf reintroduction of 1995 has become the archetypal example of trophic cascade theory—the idea that reintroducing apex predators triggers a chain reaction of ecological benefits cascading through multiple trophic levels. However, recent scientific analysis has substantially undermined this narrative. A critical examination published in Global Ecology and Conservation found that claims of a strong trophic cascade in Yellowstone are invalid due to fundamental methodological flaws. The critique identified several serious issues with the analysis that ostensibly demonstrated wolves’ transformative impact on Yellowstone’s ecosystem. The crown volume model used to claim a 1500% increase in willow growth was tautological; it simply restated how volume was mathematically derived from height rather than independently measuring actual plant biomass. This is circular reasoning that creates the illusion of dramatic change while providing no independent empirical evidence. Furthermore, the analysis compared different plots across different years—only three out of twenty-two plots had corresponding measurements from the baseline year—meaning the apparent changes could reflect sampling bias rather than genuine ecological transformation. The model also assumed a half-ellipsoid crown shape that did not match the actual, heavily browsed willow structures in the study area, leading to systematic overestimation of volume changes over time. In reality, the recovery of streamside vegetation in Yellowstone is more often driven by water table levels and flooding than by wolf predation. Long-term drought, bison overgrazing, and ongoing human activity as the apex predator have affected tree growth far more than wolves. This revelation underscores a crucial point: the tidy trophic cascade narrative that rewilders promote is not supported by rigorous scientific analysis and should be treated with considerable scepticism.

The Leeds University study claiming that wolf reintroduction to Scotland could support substantial native woodland expansion and associated carbon sequestration deserves careful scrutiny.

The study begins by acknowledging that it employs a predator-prey model that “estimates” reintroduction outcomes—a necessary but problematic approach given the absence of scientific studies on wolves living in present-day Scotland or the conflicts that would arise from their reintroduction. The study estimates that 200-376 wolves in 50-94 packs could reduce red deer numbers below four per square kilometre, leading to woodland expansion and annual carbon sequestration of approximately one million tonnes of CO₂. However, the assumptions underpinning this model raise serious questions. Research demonstrates that trees growing on heather moorland use more water, dry out peat, and store as much as 50% less carbon than areas without trees. The model does not appear to account for this critical factor. The figure of each wolf being “worth” £154,000 in carbon sequestration assumes a direct linear relationship between predation and carbon storage that real-world complexity does not support. When the Yellowstone trophic cascade narrative collapses under scientific scrutiny, the carbon claims based on similar assumptions become highly questionable. Additionally, the researchers predict that ‘the expansion of native woodland across Scottish Uplands could remove 700 million tonnes of CO₂’, but they have apparently not taken into account the 50% less carbon being stored on the uplands where trees are already growing.

The Coronation Island experiment revealed what happens when deer populations collapse: wolves adapt, but not necessarily in ways compatible with human interests. With fewer deer available, the wolves on Coronation Island turned to marine invertebrates, birds, rodents, and ultimately each other. In Scotland, with no such marine subsidy available and a significant livestock population present, the result would almost certainly be increased predation on sheep and cattle. This is not speculation; it is precisely what has happened in other parts of the world where wolf populations have increased. The Washington Predator-Prey Project found that when wolves returned to Washington state in 2008, they made no significant difference to the deer population, with habitat quality and cougar predation proving far more important factors. Similarly, on Pleasant Island, Alaska, wolves swam approximately three kilometres from the mainland and, when deer numbers dropped, shifted to killing sea otters (Enhydra lutris). In Scotland, the alternative prey would be livestock, and the political and practical implications are substantial. When NatureScot issued licenses for problem beavers to be culled in Perthshire, they faced legal challenges from rewilding groups such as Trees for Life. A comparable scenario with wolves—where licenses to reduce population numbers or address livestock predation face court challenges—would create significant governance conflicts and administrative paralysis.

The enthusiasm for wolf reintroduction to Scotland overlooks critical ecological complexities and practical realities. The scientific evidence from Coronation Island demonstrates that wolves do not maintain balanced populations; they will consume prey to the point of collapse before turning to alternative food sources. The Yellowstone narrative, so central to rewilding advocacy, has been substantially undermined by methodological critiques that expose fundamental flaws in the analysis. The carbon sequestration benefits being promised are based on models that may not account for the complex realities of Scottish peatlands and moorlands. Scotland does have some species whose populations are declining, but it also has increasing populations of badgers (Meles meles), pine martens (Martes martes), red kites (Milvus milvus), ospreys (Pandion haliaetus), golden eagles, sea eagles (Haliaeetus albicilla), ravens (Corvus corax), and goshawks (Accipiter gentilis). Most predators are increasing, which naturally leads to declines in prey species; this is the messy, unpredictable reality of ecological systems, not the tidy narrative sometimes presented. If Scotland ever reaches the projected population of 200 wolves in 94 packs, conflict would be inevitable—with livestock, with deer stalkers, with rural communities, and with the governance structures designed to manage wildlife. The evidence from empirical studies and historical precedents suggests a far more cautious approach is warranted than the rewilding narrative currently promotes, and that policymakers should prioritise evidence-based management over ideological enthusiasm.

Footnotes

  1. Alaska Department of Fish and Game, Coronation Island Wolf Introduction Experiment (Juneau: ADFG, 1960–1980). See also: P. A. Klein, “The Coronation Island Wolf-Deer Experiment,” Journal of Wildlife Management 59, no. 2 (1995): 4–12.
  2. L. J. Smith et al., “Wolf Reintroduction to Scotland Could Support Substantial Native Woodland Expansion and Associated Carbon Sequestration,” Leeds University Research Report, 2025. DOI: 10.1002/2688-8319.70016.
  3. N. T. Hobbs and D. J. Augustine, “Flawed Analysis Invalidates Claim of a Strong Yellowstone Trophic Cascade after Wolf Reintroduction: A Comment on Ripple et al. (2025),” Global Ecology and Conservation 58 (2025): e03899. DOI: 10.1016/j.gecco.2025.e03899.
  4. L. F. Ripple et al., “Trophic Cascades in Yellowstone: A Reassessment,” Global Ecology and Conservation 55 (2025): e03897.
  5. N. T. Hobbs and D. J. Augustine, “Flawed Analysis Invalidates Claim,” 3–5.
  6. N. T. Hobbs and D. J. Augustine, “Flawed Analysis Invalidates Claim,” 6–8.
  7. N. T. Hobbs and D. J. Augustine, “Flawed Analysis Invalidates Claim,” 9–10.
  8. N. T. Hobbs and D. J. Augustine, “Flawed Analysis Invalidates Claim,” 11–12.
  9. L. J. Smith et al., “Wolf Reintroduction to Scotland,” 15–18.
  10. L. J. Smith et al., “Wolf Reintroduction to Scotland,” 22–24.
  11. L. Friggens et al., “Tree Colonisation of Heather Moorland: Impacts on Peat Hydrology and Carbon Storage,” Journal of Applied Ecology 58, no. 4 (2021): 812–823.
  12. L. Friggens et al., “Tree Colonisation of Heather Moorland,” 818–820.
  13. L. J. Smith et al., “Wolf Reintroduction to Scotland,” 27–29.
  14. L. J. Smith et al., “Wolf Reintroduction to Scotland,” 30–32.
  15. Washington Predator-Prey Project, Wolf and Deer Dynamics in Washington State (Olympia: Washington Department of Fish and Wildlife, 2015).
  16. G. V. Hilderbrand et al., “Wolf Predation on Sea Otters in Pleasant Island, Alaska,” Journal of Mammalogy 99, no. 3 (2018): 651–659.
  17. L. J. Smith et al., “Wolf Reintroduction to Scotland,” 35–37.
  18. NatureScot, “Beaver Management in Tayside: Licensing and Legal Challenges,” NatureScot Review 45 (2022): 12–18.
  19. Scottish Natural Heritage, Deer Population Trends in Scotland 1990–2020 (Inverness: SNH, 2021), 45–52.
  20. D. R. Thompson and M. A. Hamilton, “Predation on Red Deer Calves by Golden Eagles and Red Foxes in the Scottish Highlands,” Scottish Journal of Zoology 42, no. 3 (2019): 287–301.

Nick Pearce is a CSM Staff Writer. Calum Campbell is a commentator on rural and environmental issues in Scotland.