A doctoral thesis evaluates the effectiveness of birds of prey to prevent farm vole pests

    The thesis studies the applications of biological control using birds of prey as a tool to prevent agricultural pests of peasant vole, as well as the potential effects of this method on other non-target wildlife species and on the transmission dynamics of pathogens such as tularemia.


    In Europe, common vole (Microtus arvalis) It is considered the vertebrate species that produces the greatest agricultural damage during periods of high population density. Starting in the 1970s, the species colonized most of the cereal-growing plains of the northern sub-plateau of the Iberian Peninsula. Since practically the beginning of this geographical expansion there have been regular population explosions, accompanied by significant agricultural damage.

    During plague episodes, rodent population control has been carried out systematically through chemical control campaigns based on the application of anticoagulant rodenticides. However, due to the serious negative effects that this type of chemical treatment has on ecosystems, for years it has been suggested that development of biological control techniques as sustainable alternatives to protect crops.

     

    The peasant vole has colonized Tierra de Campos and is the cause of important ecological and socioeconomic impacts during the periods in which it becomes a pest.

    A doctoral thesis from the University of Alcalá, defended by the recently appointed doctor Alfonso Paz Luna, and directed by the researchers Javier Viñuela and Juan Antonio Fargallo, from the Research Group in Game Resources and Wildlife Management of the Instituto de Investigación en Recursos Cinegéticos (IREC – CSIC, UCLM, JCCM) and the Department of Evolutionary Ecology of the National Museum of Natural Sciences (CSIC), respectively, have evaluated the applications of biological control through birds of prey as a tool to prevent agricultural pests of peasant vole.

    In it, they have explored the effectiveness of biological control by predation in agricultural ecosystems of the Iberian Peninsula that are highly deforested and where both damage has been recorded due to the presence of peasant vole and Mediterranean vole (Microtus duodecimcostatus). For this they selected two species of native predators whose populations can be increased relatively easily by installing nest boxes: the common kestrel (Falco tinnunculus) and the barn owl (Tyto alba).

    The results of the different scientific works that make up the doctoral thesis have shown that the installation of nest boxes was effective in reducing the abundance of both vole species at the local scale, especially in crops of alfalfa and fruit trees. They also observed how the abundance of peasant voles decreased in the vicinity of occupied nest boxes.

    Regarding possible adverse effects on other bird species, a negative effect of nest boxes on the abundance of two common bird species in agricultural environments, the cowboy washerwoman (motacilla flava) and the white wagtail (motacilla alba). Considering the possible effects of biological control on a hunting species, specifically the red partridge (Alectoris rufa), in this thesis have found that the presence of nest boxes can vary the detectability in the density estimates depending on the census methodology used.

    In relation to the dynamics of the transmission of pathogens such as tularemia (Francisella tularensis) in populations of peasant vole, it has been observed that during a period of high density of this small mammal, the prevalence of tularemia was higher in the vicinity of the nest boxes, indicating that predation could favor the prevalence of the bacterium due to the negative effects of stress on the immune response of voles. No cases of tularemia in humans were recorded in the municipalities with the highest prevalence observed in voles, which suggests that other factors could be involved in the epidemiology of tularemia in humans.