Using population models to assess extinction risk and evaluate management actions for species threatened by hybridization

Anthropogenic hybridization is increasing worldwide with unpredictable outcomes for species persistence. Accurately quantifying anthropogenic hybridization in threatened populations is fundamental for assessing extinction risk and for elaborating conservation measures. Hybridization between wolves (Canis lupus) and dogs (Canis lupus familiaris) is an emblematic case that is raising concern for wolf conservation across several countries. Nonetheless, no attempts have been made to use quantitative methods to estimate the relative abundance of admixed individuals in parental wolf populations (prevalence), predict expected hybridization outcomes and elaborate management strategies. We developed quantitative methods to: i) formally estimate prevalence of admixed individuals in parental populations; ii) estimate probability of genomic extinction due to hybridization; iii) identify effective management alternatives. Based on a non-invasive survey of an admixed wolf population in the Northern Apennines (Italy), we estimated prevalence using a multievent capture-recapture modelling approach. We then used a stage-based matrix population model to simulate trajectories of the admixed population. We then performed a sensitivity analysis to identify the parameters that most affect genomic extinction probability of the parental wolf population. We estimated a remarkably high prevalence of admixed individuals of 0.74 (0.71-0.76) in our study population, comprising admixed backcrosses of various generations. Alpha individuals’ survival affected probability of wolf genomic extinction the most, followed by frequency of mating with dogs, access to reproduction, and annual wolf per capita fertility rate. Our results conrm that hybridization with dogs should be expected, under certain conditions, to be a serious threat to the wolf genomic integrity. To reduce extinction risk, management measures aimed at preserving the social and reproductive integrity of parental species, along with reducing the occurrence of interbreeding, represent effective and socially acceptable means to counteract extensive introgression. The removal and/or sterilization of admixed individuals may still be necessary to reduce prevalence in compromised situations.