The regulation of wild populations influenced by density (where changes in abundance induce competitive interactions that affect vital rates) is typically assessed by collecting time series of population counts. In the case of mammals, whether terrestrial or marine, density-dependent changes in vital rates can occur in an apparent theoretical sequence, affecting population persistence. However, evaluations based on changes in vital rates of invasive populations completely removed (complementing population regulation studies) are less common. Understanding how these changes occur in biological invasion contexts can improve management decisions for invasive species populations.

The North American beaver (Castor canadensis) is a territorial semiaquatic rodent. Harvested populations have lower densities and higher beaver kit proportions. Introduced to Tierra del Fuego, beavers invaded all watercourses. To assess whether differences in population density and/or vital rates induced by hunting align theoretically with density-dependent population regulation, we analyzed using a descriptive-comparative approach the effects of various population management histories on 1121 invasive beavers (C. canadensis) eradicated between 2016 and 2018 from seven areas in Tierra del Fuego (Argentina) on its density, survivorship, reproductive value, generation time, breeding onset, and age distributions.

The areas with historical management (with sustained hunting) and one area that was reinvaded after being previously cleared in 2014 (reinvaded post-eradication) exhibited the highest densities and vital rates consistent with a relaxation of density dependence: age distribution with high proportion of beaver kits, shorter generation times, high reproductive value, and lower survivorship compared to areas with null management (without previous hunting).

Areas with null management presented vital rates reflecting density dependence: higher survivorship of young, delayed breeding onset, lower offspring production, higher survivorship of adults, and low proportion of beaver kits.

Practical implication. At the local level, the density-dependence on vital rates of invasive beavers could be driven, at least in part, primarily by the effect of management history rather than by population density. Continuous but irregular management over time will increase density and exacerbate spatial damage caused by beavers, while leaving previously unmanaged areas alone may result in relatively low densities but eventually achieve density-dependent vital rates, thereby compromising environmental restoration efforts.