Conservation science is a relatively young crisis discipline facing a rapid and increasing global loss of biodiversity with anthropogenic causes. Despite its constant evolution, conservation science is still riddled with challenges and uncertainties related to understanding and measuring success as well as achieving effective multidisciplinarity. Conservation translocations, the human-mediated movements of wildlife species for conservation benefits, embody conservation science paradigms and the challenge of delivering positive outputs. Specifically, a wide range of socio-ecological factors and difficulties shape the outcomes of conservation translocations and reintroduction biology - the recent sub-discipline born to study these measures - is still struggling in engaging effectively with decision-making and consider their socio-ecological dimensions in an integrated way.

Here, we investigated conservation translocations in their ecological and social dimensions, seeking to build a comprehensive understanding of how diverse factors can synergically shape translocation outcomes and, hence, success. We focused on conservation translocations targeting birds of prey (hereafter raptors), given their role in socio-ecological systems, their often-endangered status and, therefore, their resulting inclusion in many conservation translocations. In particular, we studied the proposed reintroduction of hen harriers Circus cyaneus to southern England (hereafter the Southern reintroduction), a locally-endangered species at the centre of a long-standing conservation conflict in the United Kingdom.

We developed a multidimensional framework to study conservation translocations, where social and ecological dimensions are addressed at the individual and population levels. We used a multi-pronged approach based on the literature on raptor translocations as well as qualitative and quantitative data related to socio-political and ecological aspects of the Southern reintroduction.

We found that success is yet to be fully conceptualised and investigated in a holistic way in the literature on raptor translocations. Rare definitions and assessments of success are biased towards ecological considerations even though the challenges most frequently reported by practitioners are socio-political. We advised on the need for a new evaluation framework, that considers the multiple dimensions of translocations while also acknowledging the subjective component of success definition and evaluation.

Using Discourse Network Analysis, we identified characteristics and dynamics of the stakeholder debate on the conservation and management of hen harriers in the UK in national newspaper media. The debate is characterised by the presence of vocal stakeholders and has become more polarised over time. Stakeholder coalitions diverge, especially over a conservation measure (i.e. the brood management scheme), but also share common discursive ground in the form of emotional reactions associated with hen harriers and the acknowledged need for collaboration.

Through means of participant observation and semi-structured interviews, we disclosed generally favourable perspectives of local stakeholders in Salisbury Plain on the Southern reintroduction. We found key aspects of the engagement practice such as types of engagement activities, timing, and team composition shape engagement and social processes. We showed how these aspects are linked to the positive transformative potential of the Southern reintroduction for the conservation conflict in the UK.

We explored the movement behaviour of hen harriers from the reintroduction source population in France. Using Hidden Markov Models (HMMs) and Integrated Step Selection Analysis (ISSA) to analyse, we determined land cover preferences. These showed an overall preference for arable land with differences based on behavioural states (resident and dispersal) and sex. Arable land is also associated with hen harriers transitioning to a resident state.

Finally, we developed a population viability modelling approach aimed at simulating socio-ecological realism. By using this novel individual-based model, we showed the potential viability and spatial distribution of the reintroduced population of hen harriers under increasingly informed and complex scenarios where female demographic traits and farming operations significantly affect population establishment.

Our findings provide decision-makers, practitioners, and stakeholders involved in the Southern reintroduction with essential information that can be used to inform current and future stages of this conservation programme. Most importantly, we provided conservation practitioners and researchers with a novel multidimensional framework that can be used in conservation programmes, including but not limited to translocations, to investigate their socio-ecological dimensions at different scales. Overall, this work contributes to a better understanding of the roles of both ecological and social drivers in
conservation translocations, concluding with the recommendation that redefining reintroduction biology to translocation science would result in a more representative acknowledgement of the broad range of factors influencing translocation success.