Wolf Reintroduction and Ungulate Recovery on an Isolated Range
An isolated 2,500 km² mountain range lost its apex predator, the gray wolf, around 1930. Since then, elk numbers have grown from an estimated 2,000 to 9,000, and riparian willow and aspen regeneration has failed along most streams. A proposal would reintroduce 30 wolves over three years. Biologists estimate each wolf consumes 12-18 elk per year and that the range can support 40-60 wolves at carrying capacity. Local ranchers report about 200 sheep and 150 cattle graze the range seasonally and fear depredation. A separate proposal would instead fund hunting permits to reduce elk by 3,000 animals over five years.
1. Evaluate the two proposals as trophic cascade interventions. Which is more likely to restore riparian vegetation, and why?
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Wolf reintroduction is more likely to produce a trophic cascade. Predation does more than remove elk biomass: it alters elk behavior, dispersing herds and reducing concentrated browsing in riparian corridors, which allows willow and aspen to regenerate. A hunting program reduces numbers but generally does not reproduce the landscape-of-fear effect, and hunters often target animals in accessible areas, so browsing pressure on remote riparian zones may persist. The arithmetic also matters: 30 wolves at 12-18 elk each is roughly 360-540 elk/yr, far less than the 3,000 removed by hunting, yet the behavioral mechanism can be disproportionately effective. The judgment call favors wolves for vegetation recovery, with monitoring.
2. Identify the main ecological and social risks of the wolf proposal and how they could be mitigated.
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Ecological risks: the range is isolated, so a small founding population (30) risks inbreeding and stochastic loss; 40-60 wolves is carrying capacity, so growth is bounded; and prey depletion is unlikely at these numbers but should be monitored. Livestock depredation is the key social risk. Mitigation: introduce enough founders for genetic diversity, connect or augment the population if possible, use guardian animals, night penning, and compensation programs, and target removals of problem wolves. The judgment call: the ecological case is sound, but success depends on social license, so rancher compensation and adaptive lethal control are part of the design, not afterthoughts.