A snapshot of the wild boar population in Catalonia: twice as many animals per km² as in the early 2000s

BarcelonaIn the early 2000s, the wild boar population density in Catalonia was around three and a half animals per square kilometer. This meant that approximately 106,000 wild boars roamed the Catalan fields and forests. Today, 25 years later, the number of wild boars in Catalonia has risen to around 200,000. In fact, according to the latest data from Wild boar population monitoring program in Catalonia According to the Department of Agriculture, Livestock, Fisheries and Food, in the 24-25 season the density of wild boars per km² in Catalonia reached 6.4 km², almost double that at the beginning of the millennium.

Although the wild boar population density has decreased considerably in recent years—in the 2021-22 season there were 8.76 wild boar per km², two points higher than the current figure—the dramatic increase in the presence of these animals is more than evident when compared to data from a quarter of a century ago. This overpopulation has once again become the focus of debate after Catalonia has detected cases of African swine fever (ASF) in wild boars in CollserolaA virus that had not been detected in the country since 1998.

The density of wild boar in Catalonia is currently "excessive," according to annual reports from specialists and the entities and administrations responsible for the wild boar monitoring program. Therefore, they deem it necessary to continue with population control strategies, prioritizing areas where the number of wild boar per km² is highest.

Several factors lie behind the rise in the wild boar population: from the evolution of agriculture to the consequences of keeping Vietnamese pot-bellied pigs as pets. "If you were to create a Google Earth map of Catalonia from 70 years ago, you would see that a large part of the territory consisted of carefully cultivated monoculture crops, and therefore, it wasn't a place where wild boar felt comfortable," explains wildlife veterinarian Carles Conejero, PhD from the Autonomous University of Barcelona (UAB), whose Barcelona faculty focused on wild boar. According to the expert, who currently runs a company specializing in the capture, handling, and management of urban wildlife, the problem began forty years ago: "When these crops were abandoned, they gave way to young, uncultivated forests, full of twigs and spaces where an animal could hide and live safely."

From three piglets per wild boar to a dozen

In addition to the growing areas where wild boar feel comfortable, which Conejero insists must be managed just like forest fire prevention, there's the fact that this animal has the highest reproductive rate of all hoofed animals. A female can reproduce once she reaches 30 kg, and in her first litter she can have three piglets, while in her second litter she can have up to six. However, the veterinarian explains that, normally, in a "natural" environment, a female reaches 30 kg in a year or a year and a half, while in urban areas they reach this weight threshold at six months of age and, therefore, begin reproducing much earlier. The reason is that wild boar have become accustomed to sharing space with people, and urban areas offer them more readily available food, such as garbage scraps or food given to other animals. The UAB doctor warns that one of the remaining challenges in managing the wild boar population is reaching an agreement with animal welfare organizations that feed other stray animals. "Almost every time we find a wild boar, there's a cat colony very close by. Cat food is very tasty, and wild boars can smell it from miles away," Conejero insists.

In addition to the premature nature of their reproduction, there's another factor that explains the wild boar's expansion: hybridization with Asian pig breeds, something that occurred especially around 2010, with the growing popularity in Catalan households of raising them. to have a Vietnamese pot-bellied pig as a pet, the animal from the TV3 seriesSow Misery. "If on average a wild boar has between three and six piglets, an Asian variety can have up to sixteen per birth," explains the veterinarian, who also says that his team has even found a wild boar sow hybridized with a Vietnamese pig that weighed 130 kg and was carrying up to thirteen piglets.

The presence of these animals is worrying experts in the wild boar monitoring program, who emphasize in their annual reports the need to capture them as quickly as possible to prevent them from remaining in the wild and potentially interbreeding with wild boars, due to the potential harm this could cause. Beyond being potential carriers of certain diseases, one of the main problems associated with wild boars is the damage they cause, especially when they approach areas inhabited by humans. In fact, according to data from the Department of Agriculture, Livestock, Fisheries and Food, wild boars are responsible for half of the damage caused by animals in Catalonia, which is recorded through hunting permits issued when an abundance of a particular species has caused damage or poses a danger to agriculture or livestock.

Wild boar were responsible for almost half (49%) of these cases, with over a thousand during the 2024-2025 season, far surpassing the figures for the second most frequent culprit: rabbits, which were behind 238 cases, 11% of the total.

Alt Empordà and the Guilleries, a wild boar paradise

Although in recent days the focus of wild boar management has been on Collserola because it is the epicenter of African swine fever (ASF) and because of its proximity to the Catalan capital, according to data from Wild boar population monitoring program in CataloniaIn the 2024-2025 season, the highest wild boar counts per square kilometer were recorded at the Alt Empordà (14.7) and Guilleries-Savassona (12.6) natural area observation points. During the last season, a density of 9.2 wild boar per square kilometer was also recorded at the Montnegre-Corredor observation point and 9.1 at the Montseny observation point. Conversely, the lowest densities were found at the Cadí and Boumort observation points, with a rate of 2.7 in both cases. In this regard, Conejero points out that male wild boar tend to disperse and that some individuals have been found to have traveled more than 600 kilometers, so densities in different areas can vary from season to season. In fact, he explains that by tagging wild boars, they have found animals that, in just fifteen days, had been seen in La Floresta (Sant Cugat del Vallès), Molins de Rei, Esplugues, and in the Parc del Matadero in Barcelona's Eixample district. Despite this movement, the veterinarian insists that, ultimately, the areas with the highest wild boar density are those where "the ecosystem allows it," and he gives the example of the Garrotxa region. "In that area, the density of holm oaks and oaks, and therefore the production of acorns—one of the wild boar's main food sources—is higher than that of the forests around Tortosa," he explains. The acorn production of trees like the holm oak and oak also explains one of the reasons why drastic increases (and decreases) in wild boar density are observed every three or four years. "All acorn-producing trees synchronize their production, so every four years there's one in which they reach 100% capacity," explains Conejero, who adds that during this period there's a "population boom" of the species that feed on this fruit. However, he also warns that the year after this peak, not all the trees produce acorns, and some of this overpopulation dies from lack of food.

More than 60,000 captures per year

Given the high number of incidents involving wild boars and the damage they cause to crops, specialists have studied different ways to control these pig populations due to the risks associated with their increasing density. Currently, the main method of Controlling the wild boar population means capturing themLast year, 68,694 wild boars were captured, about 5,000 fewer than the previous year, but 10,000 more than in 2017.

Regarding capture and hunting, the veterinarian asserts that the killing of the animals "has become taboo" and that hunting has been relegated to a leisure activity rather than a management technique. Another technique proposed to reduce the overpopulation of these pigs is sterilization with a contraceptive vaccine, but Conejero warns that it is "not logistically viable" to apply it in environments like Collserola Park. For the measure to be effective in this area, 70% of the fertile females would have to be captured and sterilized, and according to Conejero, this vaccine—which renders the animal sterile for one to two years—would only be effective in environments where the animals are kept in enclosed spaces.

Collserola Management

Although the presence of wild boar in Catalonia has skyrocketed since the late 1990s, in the last three years the Collserola area has experienced a drastic decrease in these animals to the point that, in the latest assessment of Wild boar population monitoring program in CataloniaThe density of wild boar was 4.09 per km², three times lower than in Alt Empordà and Les Guilleries. In the 2022-2023 season, after years of sustained growth, the area reached 9.6 wild boar/km². "In Barcelona, ​​in the last two years we have reduced wild boar incidents by 70%, a clear indicator of success," argues Conejero.

In this regard, the creation of the Wild Boar Roundtable two years ago was key, as it proposed 98 actions that went beyond hunting to manage the species. "Measures have been taken to ensure that the urban environment is not unattractive to wild boar," explains the veterinarian. These include, for example, clearing vegetation in wooded areas, sealing litter bins, and reducing vegetation in some parks.