Wolves and Hybridization

Abstract

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Introgressive hybridization between wolves and dogs is a conservation concern due to its potentially deleterious long-term evolutionary consequences. European legislation requires that wolf–dog hybridization be mitigated through effective management. We developed an individual-based model (IBM) to simulate the life cycle of gray wolves that incorporates aspects of wolf sociality that affect hybridization rates (e.g., the dissolution of packs after the death of one/both breeders) with the goal of informing decision-making on management of wolf–dog hybridization. We applied our model by projecting hybridization dynamics in a local wolf population under different mate choice and immigration scenarios and contrasted results of removal of admixed individuals with their sterilization and release. In several scenarios, lack of management led to complete admixture, whereas reactive management interventions effectively reduced admixture in wolf populations. Management effectiveness, however, strongly depended on mate choice and number and admixture level of individuals immigrating into the wolf population. The inclusion of anthropogenic mortality affecting parental and admixed individuals (e.g., poaching) increased the probability of pack dissolution and thus increased the probability of interbreeding with dogs or admixed individuals and boosted hybridization and introgression rates in all simulation scenarios. Recognizing the necessity of additional model refinements (appropriate parameterization, thorough sensitivity analyses, and robust model validation) to generate management recommendations applicable in real-world scenarios, we maintain confidence in our model’s potential as a valuable conservation tool that can be applied to diverse situations and species facing similar threats.

Abstract
Wolf-dog hybridisation (WDH) – a form of anthropogenic introgressive hybridisation – may have occasionally occurred since the times of domestication. More recently, however, despite the ongoing recovery of wolf populations in Europe, the high number of domestic dogs along with marginal ecological conditions may pose increased risks to their genetic integrity. Accordingly, WDH is currently recognised among the highest threats to European wolves, with potential cascading effects through socio-ecological systems. Based on high quality DNA from tissues of 748 wolves retrieved dead from 2020 to 2024, alongside 26 additional samples from 1993 to 2003, we assessed WDH in the peninsular Italian wolf population. Using 23 autosomal STR loci and 5 Y-linked loci for males, we detected a high proportion (46.7 %) of wolves admixed with dogs, 29.5 % of which recent hybrids and 17.2 % older backcross generations. While most of the original hybridisation events likely took place some 9–16 years ago, a few first-generation hybrids in our sample indicate that WDH is currently ongoing. This seriously threatens the genetic integrity not only of the Italian wolf population, but also of the neighbouring wolf populations through dispersal events. The situation we present, which has not been previously reported for any wolf population worldwide, serves as a cautionary example of the potential dynamics of WDH in human-dominated landscapes should the issue remain persistently unaddressed. They also highlight the importance of considering the genetic constituency of wolf populations when evaluating their conservation status, especially in light of the recent downgrading of their protection status across Europe.

Abstract
Anthropogenic hybridization between wild and domesticated forms of the same species is a significant concern in conservation biology. This problem is especially important for the gray wolf (Canis lupus), which hybridizes with the domestic dog (C. lupus familiaris) throughout its range. To understand the overlap between hybrid and wolf food niches, we compared the diet of hybrids from two locations with that of wolves from seven locations across Poland. We found that wolf × dog hybrids primarily consumed wild ungulates (95.5–100% of their food biomass), mainly Roe deer (Capreolus capreolus), Fallow deer (Dama dama), and wild Boar (Sus scrofa), and supplemented their diet with medium-sized wild mammals such as European hare (Lepus europaeus) and Eurasian beaver (Castor fiber). The diet of hybrids does not differ from that of wild wolves, and our findings confirm that wolf × dog hybrids may compete with wolves for the same food resources. Preventing wolf-dog hybridization is therefore crucial for safeguarding the ecological roles of wolves. Efforts in this area will be ineffective without reducing the free-ranging dog population and taking decisive steps to prevent dogs from entering wolf habitats.

bstract
Anthropogenic hybridisation, especially when introgressive through backcrossing into parental species, is a global threat to many wild taxa, including wolves (Canis lupus) interbreeding with dogs (C. familiaris or C. l. familiaris) (i.e., wolf-dog hybridisation, WDH). Despite the Standing Committee of the Bern Convention’s recently approved proposal to reduce the protection status of wolves from Appendix II to Appendix III, the assessment of Favourable Conservation Status (FCS) for wolves within the EU Habitats Directive does not consider anthropogenic hybridisation as a separate threat category. Hybrids being increasingly recognised as a relevant threat to European wolves, we advocate that WDH should be considered in assessing their conservation status. However, the lack of a clear and commonly accepted definition of wolf-dog hybrids has been limiting progress on legislation, policy, and conservation management. Therefore, to help mitigate the threat of WDH to wolves, we hereby propose a science-based definition of wolf-dog hybrids as a reference for conservation management. The definition is not intended to prescribe management, which will require case-by-case consideration of various factors including local regulations, conservation priorities, ethics, animal welfare, and human dimensions. It (1) provides an entity for legal and policy efforts, (2) promotes shared and transparent technical standards for hybrid identification, and (3) acknowledges the need for nuanced, population-based management policies. The definition provides an essential first step and an international reference that we envision will help mitigate the threat of WDH to wolves and preserve wolf ecological function.