Pietro Milanesi

Noninvasive sampling and genetic variability, pack structure, and dynamics in an expanding wolf population

Abstract After centuries of population decline and range contraction, gray wolves (Canis lupus) are now expanding in Europe. Understanding wolf social structure and population dynamics and predicting their future range expansion is mandatory to design sound conservation strategies, but field monitoring methods are difficult or exceedingly expensive. Noninvasive genetic sampling offers unique opportunities for the reliable monitoring of wolf populations. We conducted a 9-year-long monitoring program in a large area (approximately 19,171 km2) in northern Italy, aiming to identify individuals, estimate kinship, reconstruct packs, and describe their dynamics. Of 5,065 biological samples (99% scats), we genotyped and sexed 44% reliably using 12 unlinked autosomal microsatellites, 4 Y-linked microsatellites, and a diagnostic mitochondrial DNA control-region sequence. We identified 414 wolves, 88 dogs, and 16 wolf × dog hybrids. Wolves in the study area belonged to at least 42 packs. We reconstructed the genealogy of 26 packs. The mean pack size was 5.6 ± 2.4 SD, including adoptees, with a mean minimum pack home range of 74 km2 ± 52 SD. We detected turnovers of breeding pairs in 19% of the packs. Reproductive wolves were unrelated and unrelated dispersers founded new packs, except for 1 pack founded by a brother–sister pair. We did not detect multiple breeding females in any packs. Overall, the population was not inbred. We found significant isolation by distance and spatial autocorrelation, with nonrandom genetic structure up to a distance of approximately 17 km. We detected 37 dispersers, 14 of which became breeders in new or already existing packs. Our results can be used to model habitat use by wolves, to estimate survival rates, to predict future expansion of the wolf population, and to build risk maps of wolf–human conflicts.

European human-dominated landscapes provide ample space for the recolonization of large carnivore populations under future land change scenarios

Europe is currently being re-colonized by large carnivore species such as brown bear (Ursus arctos), Eurasian lynx (Lynx lynx) and grey wolf (Canis lupus). Approximately one-third of Europe currently hosts at least one of these large carnivore species: they show permanent occurrence in some regions and sporadic occurrence without reproduction in others. We investigated potential future range expansions of these three large carnivores using three different analyses. First, we compared niche overlap between the historical, current permanent and current sporadic occurrences using n-dimensional hypervolumes. Second, we identified the environmental variables that best explain differences between current sporadic and permanent occurrences through multi-model inference. Third, we projected permanent occurrences into the future across a range of land-use change scenarios. We also determined future refuges (i.e. sub-optimal habitat in the environmental model, good habitat in the human disturbance model) and ecological traps (i.e. good habitat in the environmental model, sub-optimal habitat in the human disturbance model). In the three large carnivores species, ecological niche overlap was higher between historical and current permanent occurrences than between historical and current sporadic occurrences, and we also found low ecological niche overlap between current permanent and sporadic occurrences. Between 20 and 24% (corresponding to 86,800 to 173,200 km2) of the current sporadic occurrences could result in permanent settlement of large carnivores in the year 2040, while 17-24% (corresponding to 122,200 to 104,100 km2) and 2.7-4.6% (corresponding to 11,800 to 28,400 km2) of the current sporadic occurrences are likely to become refuges and ecological traps, respectively. Factors affecting range expansion are human activities, which were negatively related to permanent occurrences of all three species. In light of our results, human-dominated European landscapes provide ample space for the future recolonization of large carnivores. This article is protected by copyright. All rights reserved.

Choosy Wolves? Heterozygote Advantage But No Evidence of MHC-Based Disassortative Mating

A variety of nonrandom mate choice strategies, including disassortative mating, are used by vertebrate species to avoid inbreeding, maintain heterozygosity and increase fitness. Disassortative mating may be mediated by the major histocompatibility complex (MHC), an important gene cluster controlling immune responses to pathogens. We investigated the patterns of mate choice in 26 wild-living breeding pairs of gray wolf (Canis lupus) that were identified through noninvasive genetic methods and genotyped at 3 MHC class II and 12 autosomal microsatellite (STR) loci. We tested for deviations from random mating and evaluated the covariance of genetic variables at functional and STR markers with fitness proxies deduced from pedigree reconstructions. Results did not show evidences of MHC-based disassortative mating. Rather we found a higher peptide similarity between mates at MHC loci as compared with random expectations. Fitness values were positively correlated with heterozygosity of the breeders at both MHC and STR loci, whereas they decreased with relatedness at STRs. These findings may indicate fitness advantages for breeders that, while avoiding highly related mates, are more similar at the MHC and have high levels of heterozygosity overall. Such a pattern of MHC-assortative mating may reflect local coadaptation of the breeders, while a reduction in genetic diversity may be balanced by heterozygote advantages.

Wolves and wild ungulates in the Ligurian Alps (Western Italy): prey selection and spatial-temporal interactions

Abstract We propose the integration of different non-invasive sampling methods to the study of predator-prey interactions. We analyzed the diet of the wolf (Canis lupus) to point out its elective prey and we investigated its spatial and temporal interactions with prey species from December 2012 to November 2014 in the Ligurian Alps (Southern Alps, Italy). In this area, the wolf is the only large predator, and there is a rich wild ungulate community consisting of four species. Our analyses showed that the most consumed species by wolves were the wild boar (Sus scrofa) and the roe deer (Capreolus capreolus). To successfully hunt these species, wolves need to share their spatial range, searching for them in the most suitable habitat types and in the periods of the diel cycle during which they are mainly active. Fallow deer (Dama dama) and chamois (Rupicapra rupicapra) consumption was low, and wolves showed also relatively low overlap with these species. Our results suggest that wolves might be firstly specialized on wild boar predation, as they showed substantial spatial and temporal overlap with this species, and secondly on roe deer predation, especially during the denning season when they probably take advantage of the presence of fawns.