Jacopo Cerri , Carmela Musto, Dario Capizzi, Maria Cristina Fontana, Silvia Rubini, Giuseppe Merialdi, Duccio Berzi, Francesca Ciuti, Annalisa Santi, Arianna Rossi, Filippo Barsi, Luca Gelmini, Laura Fiorentini, Giovanni Pupillo, Camilla Torreggiani, Alessandro Bianchi, Alessandra Gazzola, Paola Prati, Giovanni Sala, Marco Apollonio, Alberto Biancardi, Mauro Delogu, Laura Uboldi, Alessandro Moretti, Chiara Anna Garbarino

Second-generation Anticoagulant Rodenticides (ARs) can be particularly critical for large carnivores, due to their widespread use and time-delayed impacts on their populations. While many studies explored the impacts of ARs on small and mesocarnivores, no study explored the extent to which they could contaminate large carnivores in anthropized landscapes of Europe.

We filled this gap by exploring spatiotemporal trends in grey wolf (Canis lupus) exposure to ARs in central and northern Italy, by relying on a dataset of dead wolves (n = 186) tested with standardized laboratory protocols. The determination of anticoagulants was carried out by means of a semiquantitative LC-MS/MS method.

Most wolves (n = 115/186, 61.8%) tested positive for ARs (1 compound, n = 36; 2 compounds, n = 47; 3 compounds, n = 16; 4 or more compounds, n = 16). Bromadiolone, Brodifacoum and Difenacoum, were the most common compounds, with Brodifacoum/Bromadiolone the combination of ARs that co-occurred the most (n = 61).

Both the probability to test positive for multiple ARs and the presence of Brodifacoum, and Bromadiolone in the liver, systematically increased in wolves that were found at more anthropized sites. Moreover, wolves became more likely to test positive for ARs through time, particularly after 2020.

Our results underline that rodent control, based on ARs baiting, increases the risks of unintentional poisoning non-target wildlife. However, this risk does not only involve small and mesocarnivores, but also large carnivores at the top of the food chain, such as wolves. Therefore, rodent control is adding one further conservation threat for endangered large carnivores in anthropized landscapes of Europe, whose severity could increase through time and be far higher than previously thought. Widespread monitoring schemes for ARs in European large carnivores should be devised as soon as possible.