Contact Rates in Wild Boar Populations PODGÓRSKI, TOMASZ; APOLLONIO, MARCO; KEULING, OLIVER
The Journal of wildlife management,
August 2018, Volume:
82, Issue:
6
Journal Article
Peer reviewed
Inter-individual contacts in wildlife populations are usually highly heterogeneous. This variation translates into differential disease transmission rates between individuals, which have vital ...consequences for the spread, persistence, and control of infectious diseases. Wild boar (Sus scrofa) is an abundant game species across Europe that poses serious health threats to wildlife, livestock, and humans. However, factors shaping contact rates and structure in wild boar populations, key parameters in disease ecology, remain poorly studied. We quantified dyadic association rates, as a proxy of contacts, and individual-based network centrality measures using telemetry data from 3 wild boar populations across Europe. Next, we examined the effect of sex, age, group membership, and space use on association rates and individual centrality. Contact rates depended strongly on the distance between individual home ranges; the most frequent associations occurred at distances of 0–1 km (mostly within groups), less frequent at 1–3 km (mostly between groups), and sporadic at <4 km. Association rates were an order of magnitude higher within social groups than between them. Between-group association rates were only dependent on the distance between groups, with no apparent effect of animal sex or age. At the social network level, young animals (0.5–2 yr) showed greater between-group connectivity and a more central position in the network than adults. Our results highlight substantial contact heterogeneities in wild boar populations, which should be considered in epidemiological modeling and disease control actions. First, wild boar contact rates are strongly constrained socially and spatially. Hence, management measures reducing these constraints, such as supplementary feeding and intensive hunting, may lead to increased disease transmission rates. Second, young wild boars show exceptional connectivity within the population, highlighting their high capacity for disease transmission. Therefore, targeted removal of yearlings should be considered to optimize disease control efforts.
Roe deer (Capreolus capreolus) is the most abundant cervid in Europe and, as such, has a considerable impact over several human activities. Accurate roe deer population size estimates are useful to ...ensure their proper management. We tested 3 methods for estimating roe deer abundance (drive counts, pellet-group counts, and camera trapping) during two consecutive years (2012 and 2013) in the Apennines (Italy) in order to assess their precision and applicability. During the study period, population density estimates were: drive counts 21.89±12.74 roe deer/km2 and pellet-group counts 18.74±2.31 roe deer/km2 in 2012; drive counts 19.32±11.12 roe deer/km2 and camera trapping 29.05±7.48 roe deer/km2 in 2013. Precision of the density estimates differed widely among the 3 methods, with coefficients of variation ranging from 12% (pellet-group counts) to 58% (drive counts). Drive counts represented the most demanding method on account of the higher number of operators involved. Pellet-group counts yielded the most precise results and required a smaller number of operators, though the sampling effort was considerable. When compared to the other two methods, camera trapping resulted in an intermediate level of precision and required the lowest sampling effort. We also discussed field protocols of each method, considering that volunteers, rather than technicians, will more likely be appointed for these tasks in the near future. For this reason, we strongly suggest that for each method managers of population density monitoring projects take into account ease of use as well as the quality of the results obtained and the resources required.
Activity rhythms play an important role in the ecological relations of a species and form part of its evolutionary adaptation. Such rhythms are strongly synchronised with the annual cyclic changes by ...environmental stimuli, the so-called Zeitgebers. Animals' reliance on environmental stimuli is highly species-specific and allows behavioural adjustments to be made in preparation for the conditions expected in each season. We investigated daily and annual activity rhythms of Alpine chamois (Rupicapra rupicapra) by analysing high-resolution data of animals monitored with GPS collars. This first detailed field study of chamois activity showed that this species exhibited clear daily and annual activity rhythms entrained to the light-dark cycle. Chamois were more active during spring-summer and less active during winter, likely in response to the variation in the availability of food resources: both sexes appeared to maximise energy intake during the season offering the highest amount of food resources to compensate for poor food supply during winter. Daily activity was influenced by the climatic factors considered. We showed a negative correlation between daily activity and adverse climatic conditions (i.e. precipitation and, during winter, snow depth). As activity was strongly influenced by the interplay between temperature and wind throughout the year and by radiation and wind in winter, we conjectured that it was critically dependent upon animals' thermal balance. In conclusion, our study highlighted that chamois is well adapted to the Alpine environment and seasonality but also raised questions about its ability to adapt to future climate change.
Although many studies highlighted the potential of COVID-19 to reshape existing models of wildlife management, empirical research on this topic has been scarce, particularly in Europe. We ...investigated the potential of COVID-19 pandemic to accelerate the ongoing decline in an aging population of recreational hunters in Italy. Namely, we modelled spatiotemporal trends between 2011 and 2021 in the number of recreational hunters in 50 Italian provinces with a varying incidence of COVID-19, and temporally delayed waves of infection. Compared to projections from 2011-2019 data, we detected a lower number of hunters who enrolled for the hunting season, both in 2020 (14 provinces) and in 2021 (15 provinces). The provinces with the highest incidence of COVID-19 in the Lombardy and Emilia-Romagna regions were also those experiencing the most marked decrease in hunting participation. Our findings revealed that a wildlife management system based on recreational hunting can be rapidly destabilized by epidemics and their associated public health measures, particularly when the average age of hunters is high, like in Italy. Considered the high incidence attained by COVID-19 in many European countries, where hunters are pivotal for the management of large ungulates and where they were already declining before the pandemic, our findings call for further large-scale research about the impact of COVID-19 on hunting participation.
Wolves (Canis lupus) in Italy represent a relict west European population. They are classified as vulnerable by IUCN, though have increased in number and expanded their range in recent decades. Here ...we use 17 years of monitoring data (from 1993 to 2010) collected in a mountainous region of central Italy (Arezzo, Tuscany) in an ecological niche-based model (MaxEnt) to characterize breeding sites (i.e. the areas where pups were raised) within home ranges, as detected from play-back responses. From a suite of variables related to topography, habitat and human disturbance we found that elevation and distance to protected areas were most important in explaining the locality of wolf responses. Rendezvous sites (family play-back response sites) typically occurred between 800 and 1200 m a.s.l., inside protected areas, and were usually located along mountain chains distant from human settlements and roads. In these areas human disturbance is low and the densities of ungulates are typically high. Over recent years, rendezvous sites have occurred closer to urban areas as the wolf population has continued to expand, despite the consequent human disturbance. This suggests that undisturbed landscapes may be reaching their carrying capacity for wolves. This, in turn, may lead to the potential for increased human-wolf interactions in future. Applying our model, both within and beyond the species' current range, we identify sites both within the current range and also further afield, that the species could occupy in future. Our work underlines the importance of the present protected areas network in facilitating the recolonisation by wolves. Our projections of suitability of sites for future establishment as the population continues to expand could inform planning to minimize future wolf-human conflicts.
Density estimation is a key issue in wildlife management but is particularly challenging and labour-intensive for elusive species. Recently developed approaches based on remotely collected data and ...capture-recapture models, though representing a valid alternative to more traditional methods, have found little application to species with limited morphological variation. We implemented a camera trap capture-recapture study to survey wolf packs in a 560-km
area of Central Italy. Individual recognition of focal animals (alpha) in the packs was possible by relying on morphological and behavioural traits and was validated by non-invasive genotyping and inter-observer agreement tests. Two types (Bayesian and likelihood-based) of spatially explicit capture-recapture (SCR) models were fitted on wolf pack capture histories, thus obtaining an estimation of pack density in the area.
In two sessions of camera trapping surveys (2014 and 2015), we detected a maximum of 12 wolf packs. A Bayesian model implementing a half-normal detection function without a trap-specific response provided the most robust result, corresponding to a density of 1.21 ± 0.27 packs/100 km
in 2015. Average pack size varied from 3.40 (summer 2014, excluding pups and lone-transient wolves) to 4.17 (late winter-spring 2015, excluding lone-transient wolves).
We applied for the first time a camera-based SCR approach in wolves, providing the first robust estimate of wolf pack density for an area of Italy. We showed that this method is applicable to wolves under the following conditions:
) the existence of sufficient phenotypic/behavioural variation and the recognition of focal individuals (i.e. alpha, verified by non-invasive genotyping);
) the investigated area is sufficiently large to include a minimum number of packs (ideally 10);
) a pilot study is carried out to pursue an adequate sampling design and to train operators on individual wolf recognition. We believe that replicating this approach in other areas can allow for an assessment of density variation across the wolf range and would provide a reliable reference parameter for ecological studies.
ABSTRACT
1
Despite the vast literature on genetic variation in the domestic pig Sus scrofa, little is known about genetic differentiation in wild boar populations.
2
Here we present an up‐to‐date ...review of published data on the past and recent history of the European wild boar, its genetic diversity and the spatial distribution of genetic variation throughout the continent.
3
The phylogeography of the species seems to be shaped mostly by past large‐scale events (like postglacial recolonization) rather than by more recent human manipulation. Genetic differentiation is observed both on a continental and a regional scale, and non‐intuitive barriers to gene flow occur.
4
From an indirect estimate, hybridization between wild boar and domestic pigs is seemingly a minor source of genetic variation for wild boar populations, yet risks are still linked to the release of captive hybrids in some areas.
5
Finally, we present future perspectives concerning the development of powerful molecular tools and their possible application to the study and management of this species.
High‐density populations of large ungulates are now widespread. However, the perception of overabundance only appears when it produces a problem for humans, such as a loss of plant diversity, damage ...to agricultural crops and forestry, ungulate‐vehicle collisions, a nuisance to humans, disease transmission to livestock or changes in habitat for other species. The admissible level of density depends on the ecological and socio‐economic context in which the population is located, and defining this level is important, in order to determine management strategies and actions.
We describe the main contexts in which ungulate overabundance occurs in Europe, record the causes of overabundance and evaluate which set of indicators of ecological change is the most appropriate for monitoring and diagnosing overabundance in each scenario.
Our review of 318 published papers revealed six contexts of wild ungulate overabundance in Europe (protected areas, hunting areas, forestry, arable farming, livestock farming and periurban areas). In addition to population abundance, four sets of indicators of environmental change could be used to monitor overabundance within these contexts (impacts on habitats, impact on animal performance, increments in diseases and parasite loads, and increments in nuisance to humans).
Nine species of ungulate were found to be overabundant. Red deer Cervus elaphus was the species most likely to be overabundant in the contexts of protected areas (detailed in 27% of papers on that context) and hunting areas (38%); roe deer Capreolus capreolus in forestry (28%); wild boar Sus scrofa in arable farming (60%), livestock farming (29%) and (peri)urban areas (38%). Our evidence shows that the diagnosis and monitoring of ungulate population overabundance via indicators of ecological change, and the management actions required to control these undesirable situations, are strongly context‐dependent.
RESUMEN EN ESPAÑOL
Las poblaciones de ungulados con altas densidades están ahora muy extendidas. Sin embargo, la percepción de sobreabundancia poblacional solo aparece cuando dicha población produce un problema para los humanos, como: una pérdida de diversidad de plantas, daños a cultivos agrícolas y forestales, colisiones de vehículos ungulados, molestias para los humanos, transmisión de enfermedades al ganado o cambios en el hábitat para otras especies. El nivel de densidad admisible depende del contexto ecológico y socioeconómico en el que se encuentra la población, y es importante definir este nivel para determinar las estrategias y acciones de gestión.
Describimos los principales escenarios en los que aparecen situaciones de sobreabundancia de ungulados en Europa, registramos sus causas y evaluamos qué conjunto de indicadores de cambio ecológico es el más apropiado para monitorizar y diagnosticar la sobreabundancia en cada escenario.
Nuestra revisión de 318 artículos publicados reveló seis escenarios de sobreabundancia de ungulados silvestres en Europa (áreas protegidas, áreas de caza, silvicultura, agricultura, ganadería y áreas peri urbanas). Además de la abundancia de la población, se podrían utilizar cuatro conjuntos de indicadores para monitorizar la sobreabundancia (impactos en hábitats, impacto en el rendimiento animal, incrementos en enfermedades y cargas parasitarias, e incrementos en molestias para los humanos).
Se encontraron ejemplos de nueve especies de ungulados sobreabundantes. El ciervo Cervus elaphus fue la especie más frecuentemente sobreabundante en las áreas protegidas (detalladas en el 27% de los trabajos centrados en ese escenario) y áreas de caza (38%); el corzo Capreolus capreolus lo es en silvicultura (28%); el jabalí Sus scrofa en la agricultura (60%), ganadería (29%) y áreas (peri)urbanas (38%). Mostramos que el diagnóstico y el monitoreo de la sobreabundancia poblacional de ungulados a través de indicadores de cambio ecológico, y las acciones de gestión necesarias para controlar estas situaciones indeseables, dependen en gran medida del escenario.
We describe six contexts of wild ungulate overabundance in Europe (protected areas, hunting areas, forestry, arable farming, livestock farming and periurban areas). Protected areas are mainly devoted to conservation, where hunting of ungulates is either limited to management culling or, in a minority of cases, prohibited. Hunting areas are characterised by land where the main human activity is hunting and where hunting is carried out under commercial interests. The forestry context occurs in areas where the main land use is for forest, which is very common in northern and central Europe. The arable farming context is characterised by areas where the main land use is for growing agricultural crops. The livestock farming context occurs in land areas dedicated to animal husbandry, mainly in extensive systems, where livestock–wildlife interactions are currently frequent. Peri‐urban and urban areas are characterised by built‐up areas connected by roads and highways, as well as green areas composed of a mosaic of patches of various types.
Population dynamics studies and harvesting strategies often take advantage of body size measurements. Selected elements of the skeletal system such as mandibles, are often used as retrospective ...indices to describe body size. The variation in mandibular measurements reflects the variation in the ecological context and hence the variation in animal performance. We investigated the length of the anterior and posterior sections of the mandible in relation to the conditions experienced by juveniles of 8-10 months of age during prenatal and early postnatal life and we evaluated these parameters as ecological indicators of juvenile condition as well as female reproductive condition in a roe deer population living in the southern part of the species range. We analyzed a sample of over 24,000 mandibles of roe deer shot in 22 hunting districts in the Arezzo province (Tuscany, Central Italy) from 2005 to 2015 per age class. Mandible total length in juveniles is equal to 90% of total length in adults. In this stage of life the growing of the mandible's anterior section is already completed while that of the posterior section is still ongoing. Environmental conditions conveyed by forest productivity, agricultural land use, local population density and climate strongly affected the growth of the anterior and posterior sections of the mandibles. Conditions experienced both by pregnant females and offspring played an important role in shaping the length of the anterior section, while the size of the posterior section was found to be related to the conditions experienced by offspring. Temporal changes of the length of the anterior section are a particularly suitable index of growth constraints. Anterior section length in fact differs according to more or less advantageous conditions recorded not only in the year of birth, but also in the previous year. Similarly, the sexual size dimorphism of the anterior section of the roe deer mandible can be used to describe the quality of females above two years of age, as well as habitat value. Hence the anterior section length of the mandible and its sexual size dimorphism are indexes that can provide cues of population performance, because they capture the system's complexities, while remain simple enough to be easily and routinely used in the majority of European countries where roe deer hunting period extends from early autumn to late spring.
The Sardinian population of wild boar (WB, Sus scrofa meridionalis) has evolved on this Mediterranean island since its arrival in Neolithic age. Climate and land use vary across the island; high ...temperatures and dryness represent limiting factors for the development and reproduction of the species. Hence, the environment can have contributed to create the morphological differences we observe today across the island and could sustain the genetic structure that has been previously observed using neutral molecular markers. We therefore searched for genomic signatures of local adaptation in a sample of Sardinian WB genotyped at almost 50 K single nucleotide polymorphisms (SNPs). Genetic structure was observed in the population separating the northwest and southwest from the east of the island, where internal substructure also emerged. We identified 49 SNPs as candidate loci involved in adaptation and 61 genes. Gene ontology enrichment analysis revealed over-representation of terms related to cell localization, motility, and adhesion, but also related to anatomical development and immunity. According to our results, the environment seems to have played a role in shaping the genetic differentiation of the Sardinian wild boar in a limited evolutionary timescale.
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