The reintroduction of a flagship ungulate Capra pyrenaica: Assessing sustainability by surveying woody vegetation

Reintroductions of flagship species, including charismatic wild ungulates, are becoming increasingly frequent to protect endangered species or stimulate conservation awareness. However, indicators that go beyond the target species are still needed to ensure the ecological sustainability of past and future reintroductions. Here, we examined woody vegetation to assess the ecological sustainability 25 years after the reintroduction of a wild ungulate, the Iberian ibex or Iberian wild goat (Capra pyrenaica). We used browsing intensity, foraging preferences, regeneration probability and pellet counting to estimate sustainable population densities. Currently, almost one quarter of the woody species showed unsustainable levels of browsing. Threatened woody species were more vulnerable to ungulate damage, with 50% lacking natural regeneration. Current density estimations (47 ind km−2) represent the highest densities ever recorded for this wild ungulate species and should be reduced by an effective population control. Predicted probability on tree regeneration reveals that a 50% reduction in current densities would increase the probability of successful regeneration by nearly 60%. Browsing was found to be an efficient indicator to assess the ecological sustainability and integrate management practices. Additionally, certain woody species that are both widely distributed and highly-preferred by ungulates could work as key indicators of unsustainability. We highlight that surveying browsing and successful regeneration in woody plant communities are essential monitoring tools to provide an early warning of ungulate overpopulation and to assess the suitability of a particular area to hold new ungulates. Thus, we recommend surveying woody vegetation before and after ungulate reintroductions to ensure the ecological sustainability of highly valuable woody ecosystems.