by Joe Eaton
(Full article from RATS Tales April 2024)
Wolves are prominent in Italian myth and tradition: the she-wolf that fostered Romulus and Remus, the Wolf of Gubbio befriended by St Francis. But for centuries, actual gray wolves were vanishingly scarce there. In 1990, naturalist Gary Paul Nabhan was told that only about 300 remained. Since then, however, wolf numbers have rebounded, especially in the Apennine range; a recent nationwide population estimate was around 3000. Unfortunately, the resurgent wolves are moving into Italy’s wildland-urban interface and encountering rodenticides, among other anthropogenic dangers.
A recently-published study (The Science of the Total Environment, Jan. 2024) by Carmela Musto of the University of Bologna, Jacopo Cerri of the University of Sassari, and multiple co-authors documents pervasive exposure to anticoagulant rodenticides (ARs) in Italian wolves. Along with mountain lions in California, these wolves are among the few mammalian apex predators known to experience AR contamination, and the first such species reported from Europe. The authors found no evidence of ARs as a direct cause of death, but raise concerns about sublethal effects. Another recent paper noted an increase in cases of sarcoptic mange among wolves in northern Italy, an alarming finding in view of the known link between AR exposure and mange in California bobcats.
Of 186 wolves found dead in three northern Italian regions—Emilia-Romagna, Lombardy, and northern Tuscany— between 2018 and 2022, 115 (62%) were positive for one or more ARs, a result the authors call “largely unexpected.” The second generation ARs (SGARs) bromadiolone (97 detections) and brodifacoum (93) were the most prevalent; both were present in 61 wolves. Ten wolves were positive for the first-generation AR (FGAR) coumatetralyl. (Although the FGAR chlorophacinone is authorized for use in Italy, it was not found in any of the samples. According to Dario Capizzi, another co-author, chlorophacinone is “hardly ever used…with only four formulations still on the market.”)
Native hoofed mammals, mainly deer and wild boar, are the traditional prey of wolves in Italy. ARs have been found in boars in Spain, and in about half of a small sample in Italy. But the authors suggest that the main exposure pathway involves wolves feeding on rodents in agricultural lands and near human dwellings.Rats are easy prey for young, inexperienced wolves or for older individuals without a pack. As wildland habitat became saturated, young breeding pairs and solitary “floaters” have moved into developed lowland areas and made rats a significant part of their diet.
Nutrias (also known as coypus), large South American aquatic rodents that have become pests in North America and Europe, are also predated by Italian wolves. Using ARs to kill nutrias is illegal in Italy, but the practice persists. Intentional poisoning of wolves is also possible, and some may have consumed poisoned bait intended for truffle hunting dogs (truffle gathering in northern Italy is highly competitive).
AR poisoning was not implicated as a cause of death in any of the 115 cases, but blood-clotting disorders were present in 19. The authors acknowledge potential sublethal effects. “Overall, 137 wolves had been involved in collision with vehicles,” Jacopo Cerri said in an email exchange. “But it is hard to identify specific causes of death…For example, it is unclear if intoxicated wolves are more prone to collide with vehicles and we could not entirely rule out this possibility, although no strong evidence exists.”
Cerri and Musto were part of an earlier study published in 2021 in Global Ecology and Conservation, with an overlapping coverage area and data set. Of 200 wolves found dead from 2005 to 2021, 45 had sarcoptic mange—an apparent increase since 2007, when it was found in only two of 154 wolves. The Italian scientists know Laurel Serieys’ work on bobcats showing that AR exposure increased susceptibility to notoedric mange. “It’s an interesting study but we’re not currently working on it,” said Musto. Sarcoptic mange, she added, “is the most widespread pathogen in the Italian population.” It’s also common in red foxes in Italy, as it is in parts of North America. Musto explained that the ranges and habitats of wolves and foxes overlap in Italy, and that wolf predation on foxes could be a mechanism of transmission.
It’s not just wolves. The authors reported AR data for other mammals and birds during the 2018-2020 period in the same regions. Exposure was highest for red foxes (60 of 67) and common buzzards, Buteo hawks comparable to North American red-tailed and red-shouldered hawks (18 of 23). ARs were also found in smaller numbers of wild boars, badgers, martens, jackals, hedgehogs, hares, other hawks, owls, falcons, gulls, and corvids—a range of species that includes active predators, scavengers, herbivores, and feeders on invertebrates. Except for one detection of coumatetralyl, all the rodenticides found were SGARs.
As in the American West, the return of the wolf in Italy has inspired mixed reactions, including pressure for lethal control. The rodenticide threat is an ironic consequence of their success. To address it, Musto, Cerri, and their co-authors call for more research on the ecology of large carnivores in human landscapes, pan-European monitoring of AR effects on these iconic creatures, and tighter control of AR use.
