Too many wild boar? Modelling fertility control and culling to reduce wild boar numbers in isolated populations

Abstract

Wild boar and feral swine number and range are increasing worldwide in parallel with their impact on biodiversity and human activities. The ecological and economic impact of this species include spread of diseases, vehicle collisions, damage to crops, amenities and infrastructures and reduction in plant and animal abundance and richness. As traditional methods such as culling have not contained the growth and spread of wild boar and feral pigs, alternative methods such as fertility control are now advocated. We used empirical data on two isolated wild boar populations to model and compare the effects of different regimes of culling and fertility control on population trends. We built a Bayesian population model and applied it to explore the implications for population control of various management options combining culling and/or contraception. The results showed that, whilst fertility control on its own was not sufficient to achieve the target reduction in wild boar number, adding fertility control to culling was more effective than culling alone. In particular, using contraceptives on 40% of the population to complement the culling of 60% of the animals, halved the time to achieve our target reduction compared with culling only. We conclude that, assuming the effort of adding fertility control to culling was found to be cost-effective in terms of population reduction, these two methods should be used simultaneously if a rapid decrease in wild boar number is required for a closed population.

Factors affecting the crop damage by wild boar (Sus scrofa) and effects of population control in the Ticino and Lake Maggiore Park (North-western Italy)

“…Several studies have shown that, in open populations, a high harvest rate could be useful to obtain a fast decrease in population size (Keuling et al 2013;Bengsen et al 2014;González-Crespo et al 2018) and, in specific, applying a removal of 30-40% of post-birth population can be possible to stop population growth (Croft et al 2020;Vetter et al 2020), but applying massive culling could be costly and unrealistic in the long run. A recent study, which concerned the wild boar populations of the Castelporziano State Reserve (Croft et al 2020) in Italy also showed that in a closed population, it is necessary to have a high harvest rate, similar to what emerged from our simulations, to obtain a marked reduction of the population in a reasonable time. The authors also evaluated the effects of the simultaneous application of culling and fertility control methods which showed how integrating a realistic culling rate with fertility reduction allows to obtain significant results in a short time.…”

Improving Hunted Wild Boar Carcass Hygiene: Roles of Different Factors Involved in the Harvest Phase

“…Wild boar is the most widespread species in Europe, due to its adaptability and fertility [10,11], along with the increased availability of forest and abandoned rural areas where they can live [6]. The increased wild boar population is generating problems in some countries due to expanding contact with urban environments, such as damage to crop production, collisions with vehicles, and possible spread of zoonoses [11]. The population dynamics are generally controlled by hunters; therefore, the availability of wild boar meat is growing [3], and this could become a relevant part of regional economies not only for fresh meat production but also several typical meat products appreciated by consumers [12].…”

“…Wild boar is the most widespread species in Europe, due to its adaptability and fertility [ 10 , 11 ], along with the increased availability of forest and abandoned rural areas where they can live [ 6 ]. The increased wild boar population is generating problems in some countries due to expanding contact with urban environments, such as damage to crop production, collisions with vehicles, and possible spread of zoonoses [ 11 ].…”

The wild boar Sus scrofa as a threat to ground‐nesting bird species: an artificial nest experiment

“…Its extraordinary physiological and ecological plasticity have made it a successful invader worldwide (Barrios‐Garcia & Ballari, 2012; Massei et al ., 2015). Wild boar numbers are increasing particularly in Europe, where this species is native, emphasizing concerns about ensuing negative impacts on ecosystems and human activities (e.g., Massei et al ., 2015; Genov et al ., 2017; Croft et al ., 2020).…”